###
NeoLife is a global health and wellness company that offers a range of products designed to improve overall health and well-being. Their products for women encompass various categories, including nutrition, weight management, and skincare. In this comprehensive set of notes, we'll delve into the specific NeoLife products tailored for women, their benefits, ingredients, and usage.
### 1. **Introduction to NeoLife**
**History and Mission**
NeoLife was founded in 1958 and has since been committed to providing high-quality, scientifically researched nutritional supplements. The company's mission is to make the world a healthier and happier place by providing essential nutrients that are often lacking in modern diets.
**Philosophy**
NeoLife’s products are based on nature and backed by science. They aim to bridge the nutritional gap that many people face due to poor diet choices, busy lifestyles, and the consumption of processed foods.
### 2. **Core Product Categories for Women**
NeoLife offers a range of products that cater specifically to women's health needs. These products fall into several core categories:
- **Nutrition**
- **Weight Management**
- **Skincare**
- **Energy and Fitness**
### 3. **Nutrition**
#### **3.1. Multivitamins and Minerals**
**Formula IV Plus**
- **Description**: A comprehensive multivitamin that supports overall health.
- **Key Benefits**: Provides essential vitamins and minerals, supports energy levels, and boosts immune function.
- **Ingredients**: Vitamins A, C, D, E, B-complex, minerals like calcium, magnesium, iron, and a proprietary whole-food blend.
- **Usage**: Take one packet daily with a meal.
**Women’s Vitality Pack**
- **Description**: A targeted pack designed to meet the unique nutritional needs of women.
- **Key Benefits**: Supports bone health, hormonal balance, and overall vitality.
- **Ingredients**: Calcium, magnesium, vitamin D, omega-3 fatty acids, and a phytonutrient blend.
- **Usage**: Take one pack daily with a meal.
#### **3.2. Omega-3 Supplements**
**Salmon Oil Plus**
- **Description**: A potent omega-3 supplement derived from pure salmon oil.
- **Key Benefits**: Supports heart health, brain function, and reduces inflammation.
- **Ingredients**: Omega-3 fatty acids (EPA and DHA), vitamin E.
- **Usage**: Take three capsules daily with meals.
#### **3.3. Targeted Nutrition**
**Cruciferous Plus**
- **Description**: A supplement that provides the health benefits of cruciferous vegetables.
- **Key Benefits**: Supports detoxification, hormonal balance, and reduces cancer risk.
- **Ingredients**: Broccoli, radish, kale, black mustard, and other cruciferous vegetables.
- **Usage**: Take one tablet daily with a meal.
**Full Motion**
- **Description**: A supplement designed to support joint health and mobility.
- **Key Benefits**: Reduces joint pain, improves flexibility, and supports cartilage health.
- **Ingredients**: Glucosamine, herbal blend, and essential minerals.
- **Usage**: Take one tablet daily with a meal.
### 4. **Weight Management**
#### **4.1. Meal Replacement Shakes**
**NeoLifeShake**
- **Description**: A protein-rich meal replacement shake that supports weight loss and muscle maintenance.
- **Key Benefits**: Helps control hunger, supports muscle repair, and provides sustained energy.
- **Ingredients**: Protein blend (whey, casein, soy), vitamins, minerals, and fiber.
- **Usage**: Replace one or two meals daily with a shake.
**Tré**
- **Description**: A nutritional essence that supports weight management and overall health.
- **Key Benefits**: Boosts metabolism, supports detoxification, and provides antioxidants.
- **Ingredients**: Pomegranate, acai berry, green tea extract, and resveratrol.
- **Usage**: Take 1-2 ounces daily.
#### **4.2. Fat Burners and Metabolism Boosters**
**GR2 Control Appetite Reducer**
- **Description**: A supplement designed to help control appetite and reduce cravings.
- **Key Benefits**: Supports weight loss, reduces hunger, and promotes satiety.
- **Ingredients**: Glucomannan fiber, chromium, and herbal extracts.
- **Usage**: Take one capsule 30 minutes before meals.
**GR2 Control Thermogenic Enhancer**
- **Description**: A supplement that boosts metabolism and supports fat burning.
- **Key Benefits**: Increases energy expenditure, promotes fat loss, and enhances workout performance.
- **Ingredients**: Green tea extract, caffeine, and capsicum.
- **Usage**: Take one capsule before workouts or meals.
### 5. **Skincare**
#### **5.1. Daily Skincare Regimen**
**Nutriance Organic Hydrating Serum**
- **Description**: A hydrating serum that revitalizes and nourishes the skin.
- **Key Benefits**: Improves skin elasticity, provides deep hydration, and reduces the appearance of fine lines.
- **Ingredients**: Marine botanicals, hyaluronic acid, and essential oils.
- **Usage**: Apply a few drops to clean skin twice daily.
**Nutriance Organic Ultra Moisturizing Cream**
- **Description**: A rich moisturizing cream that provides intense hydration.
- **Key Benefits**: Nourishes dry skin, improves skin texture, and provides long-lasting moisture.
- **Ingredients**: Shea butter, jojoba oil, and marine botanicals.
- **Usage**: Apply to face and neck twice daily.
#### **5.2. Anti-Aging Solutions**
**Nutriance Organic Restorative Night Cream**
- **Description**: A night cream that supports skin regeneration and reduces signs of aging.
- **Key Benefits**: Promotes skin repair, reduces wrinkles, and improves skin tone.
- **Ingredients**: Marine peptides, antioxidants, and essential oils.
- **Usage**: Apply to face and neck before bedtime.
**Nutriance Organic Instant Lifting Serum**
- **Description**: A serum that provides an instant lifting effect and smoothens fine lines.
- **Key Benefits**: Tightens skin, reduces puffiness, and enhances radiance.
- **Ingredients**: Marine polysaccharides, aloe vera, and essential oils.
- **Usage**: Apply to targeted areas as needed.
### 6. **Energy and Fitness**
#### **6.1. Energy Boosters**
**NeoLife Tea**
- **Description**: An energizing tea blend that supports mental alertness and physical endurance.
- **Key Benefits**: Increases energy, improves focus, and provides antioxidants.
- **Ingredients**: Green tea, black tea, and natural flavors.
- **Usage**: Enjoy one to two cups daily.
**CoQ10**
- **Description**: A supplement that supports cellular energy production and cardiovascular health.
- **Key Benefits**: Boosts energy levels, supports heart health, and reduces oxidative stress.
- **Ingredients**: Coenzyme Q10, vitamin E, and mixed tocopherols.
- **Usage**: Take one capsule daily with a meal.
#### **6.2. Fitness and Muscle Support**
**Performance Protein**
- **Description**: A high-quality protein supplement that supports muscle growth and recovery.
- **Key Benefits**: Enhances muscle repair, supports strength, and provides sustained energy.
- **Ingredients**: Whey protein isolate, BCAAs, and essential vitamins.
- **Usage**: Take one serving post-workout or as needed.
**Sport Endurance**
- **Description**: A supplement designed to enhance athletic performance and endurance.
- **Key Benefits**: Increases stamina, reduces fatigue, and supports recovery.
- **Ingredients**: Amino acids, electrolytes, and herbal extracts.
- **Usage**: Take one serving before or during workouts.
### 7. **Scientific Research and Quality Assurance**
**Scientific Advisory Board**
NeoLife’s products are developed and reviewed by a team of scientists and nutrition experts. The Scientific Advisory Board ensures that all products are based on the latest scientific research and meet high standards of quality and efficacy.
**Quality Control**
NeoLife adheres to stringent quality control processes. Their products are manufactured in facilities that follow Good Manufacturing Practices (GMP) and are subject to rigorous testing for purity, potency, and safety.
### 8. **Customer Testimonials and Success Stories**
Many women have reported significant improvements in their health and well-being after using NeoLife products. Testimonials highlight benefits such as increased energy levels, better skin health, weight loss, and improved overall vitality.
### 9. **Conclusion**
NeoLife offers a comprehensive range of products designed to meet the unique health needs of women. From essential vitamins and minerals to targeted nutritional supplements, weight management solutions, and skincare products, NeoLife’s offerings are grounded in scientific research and high-quality ingredients. By incorporating these products into a daily routine, women can support their overall health, enhance their beauty, and achieve their wellness goals.
### 10. **References and Further Reading**
For more detailed information about NeoLife products and their benefits, please refer to the following resources:
- NeoLife Official Website: [www.neolife.com](https://www.neolife.com)
- NeoLife Product Catalogs
- Scientific Publications on Nutritional Supplements and Skincare
---
These notes provide a comprehensive overview of NeoLife products for women, highlighting the benefits, ingredients, and usage of each product. They serve as a useful guide for anyone looking to understand how NeoLife can support women's health and wellness.
**What They Don't Tell You About Pregnancy**
**Physical Changes and Symptoms**
1. **Morning Sickness**:
- Can occur at any time of the day, not just in the morning.
- May last beyond the first trimester.
2. **Fatigue**:
- Extreme tiredness is common, especially in the first and third trimesters.
- Rest as needed; listen to your body.
3. **Skin Changes**:
- Stretch marks, acne, and pigmentation changes (like the “pregnancy mask”).
- Itchy skin due to stretching.
4. **Digestive Issues**:
- Constipation and heartburn are common.
- Increased gas and bloating.
5. **Frequent Urination**:
- Pressure from the growing uterus on the bladder increases the need to pee.
6. **Swelling**:
- Swelling in feet, ankles, and hands due to increased fluid retention.
7. **Body Aches**:
- Back pain, pelvic pain, and leg cramps due to the added weight and changing body.
8. **Breast Changes**:
- Tenderness, enlargement, and possible leakage of colostrum.
**Emotional and Mental Health**
1. **Mood Swings**:
- Hormonal changes can lead to unpredictable emotions.
- Anxiety and depression can occur; seek support if needed.
2. **Brain Fog**:
- Forgetfulness and difficulty concentrating, often referred to as “pregnancy brain.”
3. **Body Image**:
- Changes in appearance can affect self-esteem and body image.
- Embrace the changes and seek support if struggling.
**Lifestyle Adjustments**
1. **Dietary Restrictions**:
- Avoid certain foods (e.g., raw fish, deli meats, unpasteurized cheese).
- Need for prenatal vitamins, especially folic acid and iron.
2. **Exercise**:
- Important for health, but modifications may be necessary.
- Consult with a healthcare provider about safe exercises.
3. **Sleep Disruptions**:
- Difficulty sleeping due to discomfort, frequent urination, and vivid dreams.
- Find comfortable sleeping positions, use pillows for support.
4. **Medical Appointments**:
- Frequent prenatal visits and tests.
- Monitoring for conditions like gestational diabetes and preeclampsia.
**Social and Relationship Changes**
1. **Support System**:
- Importance of a strong support system from family and friends.
- Open communication with partner about needs and concerns.
2. **Social Expectations**:
- Managing unsolicited advice and comments from others.
- Balancing work and personal life with pregnancy demands.
**Labor and Delivery Realities**
1. **Birth Plans**:
- Birth plans may not go as expected; flexibility is key.
- Be prepared for different scenarios, including potential complications.
2. **Pain Management**:
- Various pain relief options (e.g., epidural, natural methods).
- Educate yourself on choices and discuss with your healthcare provider.
3. **Postpartum Recovery**:
- Recovery time varies; includes healing from delivery and adjusting to new routines.
- Physical and emotional changes continue after birth.
**Unexpected Changes**
1. **Hair and Nail Changes**:
- Hair may become thicker during pregnancy but may shed post-birth.
- Nails may grow faster but can become brittle.
2. **Vision Changes**:
- Some women experience vision changes or increased prescription needs.
3. **Increased Sensitivity**:
- Heightened sense of smell and taste.
- Sensitivity to certain fabrics or materials.
**Financial and Practical Considerations**
1. **Costs**:
- Consider the costs of prenatal care, delivery, and baby supplies.
- Plan and budget accordingly.
2. **Work Adjustments**:
- Maternity leave policies vary; understand your options.
- Discuss plans with your employer early.
3. **Home Preparation**:
- Preparing the home for the baby (nursery, safety measures).
- Consider necessary purchases (e.g., car seats, strollers).
**Long-term Considerations**
1. **Parenting Classes**:
- Helpful to prepare for the realities of caring for a newborn.
- Topics can include breastfeeding, infant CPR, and basic baby care.
2. **Bonding and Attachment**:
- Early bonding with the baby is important for emotional development.
- Skin-to-skin contact and breastfeeding can enhance bonding.
3. **Future Planning**:
- Consider long-term plans such as child care, education, and family planning.
- Discuss and plan with your partner.
### **Conclusion**
Pregnancy is a unique journey with various physical, emotional, and practical changes. Being informed and prepared can help manage expectations and navigate the challenges. Seeking support, maintaining open communication, and staying flexible are key to a positive pregnancy experience.
---
**Introduction to Poop**
- Poop, also called stool or feces, is the waste left after digestion.
- It's a natural and essential part of the digestive process.
- Understanding poop can provide insights into overall health.
**The Digestive Process**
1. **Mouth**: Food is chewed and mixed with saliva, starting the digestion process.
2. **Esophagus**: Food travels down this tube to the stomach.
3. **Stomach**: Food is mixed with digestive juices, turning it into a liquid mixture called chyme.
4. **Small Intestine**: Nutrients are absorbed from chyme into the bloodstream.
5. **Large Intestine**: Water is absorbed from the remaining waste, forming solid stool.
6. **Rectum and Anus**: Stool is stored in the rectum until it's ready to be excreted through the anus.
**Components of Poop**
- **Water**: Makes up about 75% of poop.
- **Bacteria**: Helps break down food and produce vitamins.
- **Fiber**: Adds bulk to stool, making it easier to pass.
- **Cells and Mucus**: Help stool pass smoothly.
- **Color**: Comes from bile, a digestive fluid from the liver.
**Healthy Poop**
- **Color**: Typically brown, but can be green, yellow, or slightly red depending on diet.
- **Consistency**: Should be soft and easy to pass.
- **Shape**: Usually long and sausage-shaped.
- **Frequency**: Varies from three times a day to three times a week.
**Signs of Unhealthy Poop**
- **Color Changes**: Very dark, black, or red can indicate bleeding; very pale can indicate liver problems.
- **Consistency Changes**: Hard stools may mean constipation; watery stools can indicate diarrhea.
- **Smell Changes**: Extremely foul-smelling poop can indicate an infection or poor digestion.
- **Frequency Changes**: Significant changes in how often you poop can signal a problem.
**Common Digestive Issues**
- **Constipation**: Hard, dry stools that are difficult to pass, often due to lack of fiber or water.
- **Diarrhea**: Loose, watery stools, often caused by infections or certain foods.
- **Irritable Bowel Syndrome (IBS)**: Causes cramping, pain, bloating, and changes in bowel habits.
- **Hemorrhoids**: Swollen veins in the rectum or anus, often from straining.
- **Infections**: Bacterial, viral, or parasitic infections affecting digestion.
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**Keeping Your Digestive System Healthy**
- **Eat a Balanced Diet**: Include fruits, vegetables, and whole grains for fiber.
- **Stay Hydrated**: Drink plenty of water.
- **Exercise Regularly**: Helps stimulate digestion.
- **Eat Regular Meals**: Helps regulate your digestive system.
- **Listen to Your Body**: Don’t ignore the urge to poop.
**Poop and Mental Health**
- **Gut-Brain Axis**: Connection between gut and brain; gut health can affect mood.
- **Gut Microbiome**: Trillions of bacteria in the gut aid in digestion and affect overall health.
- **Neurotransmitters**: Gut produces serotonin, impacting mood.
- **Stress and Digestion**: Stress can cause digestive issues like stomachaches, diarrhea, or constipation.
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**Cultural Perspectives on Poop**
- **Toilets and Hygiene**: Varied practices around the world; squat toilets and bidets are common in some cultures.
- **Dietary Practices**: Traditional diets impact digestive health; high-fiber diets are common in many cultures.
- **Taboos and Discussions**: Talking about poop is taboo in some cultures but normal in others.
**Fun Facts About Poop**
- **Animals Poop Differently**: Example: rabbits produce two types of poop.
- **Poop for Communication**: Animals like wolves use poop to mark territory.
- **Guano**: Bird and bat poop used as fertilizer.
- **Bristol Stool Chart**: Tool used by doctors to categorize poop types.
- **Poop Transplants**: Fecal microbiota transplants treat certain infections.
**Environmental Impact of Poop**
- **Sewage Treatment**: Treats human waste to remove harmful bacteria and chemicals.
- **Composting Toilets**: Turn human waste into compost for use as fertilizer.
- **Livestock Waste**: Must be managed to prevent water pollution.
**Detailed Notes**
1. **What Is Poop?**
- Waste product after digestion.
- Essential for removing waste from the body.
2. **How Poop Forms**
- Starts with chewing food in the mouth.
- Travels through the esophagus to the stomach.
- Mixed with digestive juices in the stomach.
- Nutrients absorbed in the small intestine.
- Water absorbed in the large intestine, forming stool.
- Stored in the rectum until excreted.
3. **What’s in Poop?**
- Mostly water (75%).
- Bacteria that aid digestion.
- Fiber from plant foods.
- Shed cells and mucus from intestines.
- Bile from the liver gives it color.
4. **Healthy Poop Characteristics**
- Brown color from bile.
- Soft and easy to pass.
- Sausage-shaped.
- Frequency varies: 3 times a day to 3 times a week.
5. **Unhealthy Poop Signs**
- Dark, black, or red: possible bleeding.
- Pale or clay-colored: possible liver issues.
- Hard or watery consistency: constipation or diarrhea.
- Extremely foul smell: possible infection.
- Significant changes in frequency.
6. **Common Digestive Problems**
- **Constipation**: Hard, dry stools; caused by lack of fiber, water, or exercise.
- **Diarrhea**: Loose, watery stools; caused by infections or certain foods.
- **IBS**: Cramping, pain, bloating, and bowel habit changes.
- **Hemorrhoids**: Swollen veins from straining.
- **Infections**: Bacterial, viral, or parasitic.
7. **Tips for Digestive Health**
- **Diet**: Eat fiber-rich foods like fruits, vegetables, and whole grains.
- **Hydration**: Drink plenty of water.
- **Exercise**: Regular physical activity.
- **Regular Meals**: Helps regulate digestion.
- **Listen to Your Body**: Don’t hold in poop.
8. **Mental Health and Digestion**
- **Gut-Brain Axis**: Connection between gut and brain.
- **Gut Microbiome**: Bacteria in the gut aid digestion and affect health.
- **Neurotransmitters**: Gut produces serotonin, affecting mood.
- **Stress**: Can cause stomachaches, diarrhea, or constipation.
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9. **Cultural Views on Poop**
- **Toilets**: Different types (e.g., squat toilets, bidets).
- **Diet**: Traditional diets impact digestive health.
- **Taboos**: Some cultures find poop discussions taboo, others don’t.
10. **Interesting Poop Facts**
- **Animals**: Different animals have different poop habits.
- **Communication**: Some animals use poop to mark territory.
- **Guano**: Used as fertilizer.
- **Bristol Stool Chart**: Categorizes poop types.
- **Poop Transplants**: Treat certain infections.
11. **Environmental Impact**
- **Sewage Treatment**: Cleans waste before releasing it.
- **Composting Toilets**: Eco-friendly alternative, turns waste into compost.
- **Livestock Waste**: Managed to prevent pollution.
**Conclusion**
- Poop is a natural and necessary function.
- Understanding poop helps monitor health.
- Healthy diet, hydration, and exercise are key to good digestion.
- Mental health impacts digestion.
- Cultural perspectives vary, but open discussions can improve health.
---
What They Don't Tell You About Vagina Health
Vagina health is often surrounded by myths and misconceptions. Here are some important and often overlooked aspects of vaginal health:
1. **Natural Cleaning**: The vagina is self-cleaning. It naturally maintains its balance of bacteria and pH levels. Overuse of douches, scented products, or harsh soaps can disrupt this balance, leading to infections.
2. **Discharge is Normal**: Vaginal discharge is a normal bodily function and can vary throughout the menstrual cycle. It's a sign that the vagina is healthy and self-cleaning. Changes in color, consistency, or smell can indicate an issue, but daily discharge is typical.
3. **Diet Affects Vaginal Health**: What you eat can influence your vaginal health. A diet high in sugar can contribute to yeast infections, while foods rich in probiotics (like yogurt) can support a healthy balance of bacteria.
4. **Exercise Impact**: Regular exercise promotes overall health, but activities like cycling or horseback riding can cause friction and irritation. Wearing proper clothing and using protective gear can help.
5. **Sexual Health and Lubrication**: Using adequate lubrication during sex can prevent microtears and discomfort. It's also important to urinate after sex to reduce the risk of urinary tract infections.
6. **Menstrual Products**: Using tampons, pads, or menstrual cups safely is crucial. Changing them regularly helps prevent toxic shock syndrome (TSS) and other infections.
7. **Medical Check-ups**: Regular gynecological exams are essential for early detection of issues. Pap smears, HPV tests, and STI screenings can catch problems before they become serious.
8. **Mental Health Connection**: Stress and mental health can affect vaginal health. High stress levels can lead to conditions like bacterial vaginosis. Maintaining mental well-being is part of maintaining physical health.
9. **Impact of Hormones**: Hormonal changes throughout life (puberty, pregnancy, menopause) affect vaginal health. Understanding these changes helps in managing symptoms and maintaining health during these phases.
10. **Clothing Choices**: Tight clothing and non-breathable fabrics can create a warm, moist environment that promotes bacterial growth. Cotton underwear and loose clothing help maintain a healthy environment.
Understanding these aspects helps in maintaining vaginal health and preventing common issues. Always consult a healthcare provider for personalized advice.
Certainly! Lowering cholesterol levels is important for maintaining heart health and overall well-being. Here's a comprehensive guide in simple language on how to lower cholesterol:
---
# How to Lower Cholesterol: A Simple Guide
## Introduction
Cholesterol is a fatty substance found in your blood that is necessary for building healthy cells. However, high levels of cholesterol can increase your risk of heart disease and stroke. Lowering cholesterol involves making healthy lifestyle choices and sometimes using medications under medical supervision. This guide will explore effective strategies to lower cholesterol naturally and improve your heart health.
## Understanding Cholesterol
Cholesterol is categorized into two types: LDL (low-density lipoprotein) and HDL (high-density lipoprotein). LDL cholesterol is often referred to as "bad" cholesterol because high levels can lead to plaque buildup in your arteries, increasing the risk of heart disease. HDL cholesterol, on the other hand, is known as "good" cholesterol because it helps remove LDL cholesterol from your bloodstream.
## Lifestyle Changes to Lower Cholesterol
### 1. **Healthy Eating Habits**
- **Choose Heart-Healthy Fats:** Opt for unsaturated fats found in olive oil, avocados, nuts, and seeds rather than saturated fats found in red meat, butter, and full-fat dairy products.
- **Increase Fiber Intake:** Eat more fruits, vegetables, whole grains, and legumes to help lower LDL cholesterol levels.
- **Limit Trans Fats:** Avoid foods with trans fats, often found in fried and processed foods, as they can raise LDL cholesterol.
- **Reduce Dietary Cholesterol:** Limit foods high in cholesterol, such as egg yolks and organ meats.
### 2. **Regular Exercise**
- **Aim for Aerobic Exercise:** Engage in activities like brisk walking, jogging, swimming, or cycling for at least 150 minutes per week to improve cholesterol levels.
- **Include Strength Training:** Incorporate resistance exercises like weightlifting or bodyweight exercises to boost HDL cholesterol.
### 3. **Maintain a Healthy Weight**
- **Calorie Control:** Balance the number of calories you consume with those you burn through physical activity.
- **Healthy Portions:** Practice portion control to prevent overeating and maintain a healthy weight.
### 4. **Quit Smoking**
- **Benefits of Quitting:** Smoking lowers HDL cholesterol levels and damages the walls of your blood vessels, increasing the risk of heart disease. Quitting smoking can improve cholesterol levels and overall heart health.
### 5. **Manage Stress**
- **Stress Reduction Techniques:** Practice relaxation techniques such as deep breathing, meditation, yoga, or hobbies to reduce stress levels, which can impact cholesterol levels.
## Medical Treatment Options
### 1. **Medications**
- **Statins:** Prescription medications that lower LDL cholesterol levels by blocking a substance your body needs to make cholesterol.
- **Other Medications:** Your doctor may prescribe other medications, such as bile acid sequestrants, cholesterol absorption inhibitors, or PCSK9 inhibitors, depending on your cholesterol levels and health status.
### 2. **Regular Monitoring**
- **Cholesterol Tests:** Regular blood tests (lipid panel) to monitor cholesterol levels and assess the effectiveness of lifestyle changes and medications.
## Conclusion
Lowering cholesterol levels is essential for reducing the risk of heart disease and improving overall health. By adopting healthy eating habits, engaging in regular physical activity, maintaining a healthy weight, quitting smoking, managing stress, and potentially using medications under medical supervision, you can effectively lower cholesterol levels and support your heart health. Consult your healthcare provider for personalized advice and guidance tailored to your specific needs and health status.
---
This guide provides practical advice in simple language to help you understand and implement strategies for lowering cholesterol levels naturally and improving your heart health.
# NeoLife and its Role in Addressing Cancer, Malaria, and Cholera
## Introduction
NeoLife is a global health and wellness company committed to improving lives through superior nutrition. Founded in 1958, NeoLife offers a range of nutritional supplements, weight management products, and personal care items designed to support optimal health. Over the decades, NeoLife has built a reputation for scientific excellence and product efficacy. This article explores the role of NeoLife products in addressing three significant health challenges: cancer, malaria, and cholera.
## Cancer: A Global Health Challenge
### Understanding Cancer
Cancer is a complex group of diseases characterized by the uncontrolled growth and spread of abnormal cells. It can develop in virtually any organ or tissue of the body and is one of the leading causes of death worldwide. The primary factors contributing to cancer include genetic mutations, lifestyle factors (such as smoking, diet, and physical activity), environmental exposures, and infections.
### NeoLife’s Approach to Cancer Prevention and Support
NeoLife emphasizes the importance of a holistic approach to health, which includes balanced nutrition, regular physical activity, and maintaining a healthy lifestyle. While no supplement can cure cancer, certain nutrients have been shown to support the body’s natural defenses and potentially reduce the risk of developing cancer.
#### Antioxidants and Cancer Prevention
Antioxidants are compounds that protect cells from damage caused by free radicals, which are unstable molecules that can damage DNA and other cellular components, leading to cancer. NeoLife offers several products rich in antioxidants, including:
- **Carotenoid Complex**: This supplement contains a blend of carotenoids, such as beta-carotene, lycopene, and lutein, derived from fruits and vegetables. Carotenoids have been shown to enhance immune function and protect cells from oxidative damage.
- **Flavonoid Complex**: Rich in flavonoids from a variety of fruits and vegetables, this product provides powerful antioxidant protection and supports cardiovascular health.
- **Cruciferous Plus**: Contains extracts from cruciferous vegetables like broccoli, kale, and Brussels sprouts. These vegetables are known for their cancer-protective properties, particularly in reducing the risk of hormone-related cancers.
#### Omega-3 Fatty Acids and Inflammation
Chronic inflammation is a known risk factor for cancer development. Omega-3 fatty acids, found in fish oil and certain plant oils, have anti-inflammatory properties and may help reduce the risk of cancer. NeoLife’s **Omega-3 Salmon Oil Plus** provides a rich source of omega-3 fatty acids, including EPA and DHA, which support overall health and reduce inflammation.
### Supporting Cancer Patients
For individuals undergoing cancer treatment, maintaining optimal nutrition is crucial. Cancer and its treatments can lead to malnutrition, weight loss, and a weakened immune system. NeoLife offers several products that can help support nutritional needs during this challenging time:
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals. It can be particularly beneficial for cancer patients who have difficulty eating solid foods.
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants. It supports overall health and vitality.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
## Malaria: An Enduring Threat
### Understanding Malaria
Malaria is a life-threatening disease caused by parasites transmitted to humans through the bites of infected mosquitoes. Despite significant progress in reducing malaria cases and deaths, it remains a major public health challenge, particularly in sub-Saharan Africa. Symptoms of malaria include fever, chills, headache, and, in severe cases, organ failure and death.
### NeoLife’s Role in Malaria Prevention and Support
Preventing and managing malaria involves a multifaceted approach, including the use of insecticide-treated bed nets, indoor residual spraying, and prompt treatment with antimalarial medications. While nutritional supplements cannot replace these primary interventions, they can play a supportive role in enhancing the body’s immune response and overall health.
#### Immune Support
A strong immune system is vital for defending against infections, including malaria. NeoLife offers several products that can help boost immune function:
- **Vita-Squares**: A multivitamin and mineral supplement designed for children, providing essential nutrients to support growth and immune health.
- **Vitamin C Sustained Release**: Provides a steady release of vitamin C, an important antioxidant that supports immune function and helps the body fight infections.
- **All-C**: A chewable vitamin C supplement that provides antioxidant protection and supports immune health.
#### Nutritional Support During Malaria
Malaria can lead to significant nutritional deficiencies due to loss of appetite, vomiting, and increased metabolic demands. NeoLife’s nutritional supplements can help address these deficiencies and support recovery:
- **Formula IV Plus**: A comprehensive multivitamin and mineral supplement that provides essential nutrients for overall health and vitality.
- **Phytodefense**: Contains a blend of fruit and vegetable extracts rich in phytonutrients and antioxidants, supporting immune function and overall health.
### Collaborations and Community Programs
NeoLife has been involved in various community programs aimed at improving health and nutrition in malaria-endemic regions. These initiatives often include education on the importance of nutrition and the distribution of supplements to vulnerable populations.
## Cholera: A Preventable Disease
### Understanding Cholera
Cholera is an acute diarrheal illness caused by the ingestion of food or water contaminated with the bacterium *Vibrio cholerae*. It can cause severe dehydration and death if not treated promptly. Cholera outbreaks often occur in settings with inadequate water and sanitation infrastructure.
### NeoLife’s Role in Cholera Prevention and Support
Preventing cholera involves ensuring access to clean water, proper sanitation, and hygiene practices. Nutritional support can also play a role in bolstering the body’s defenses and aiding recovery.
#### Hydration and Electrolyte Balance
The primary treatment for cholera involves rehydration to replace lost fluids and electrolytes. While NeoLife does not offer specific products for rehydration, maintaining overall health and nutrition can help support recovery:
- **NeoLifeTea**: A naturally flavored tea that provides hydration and contains antioxidants to support overall health.
- **NeoLifeShake**: Provides balanced nutrition and can be part of a rehydration strategy when combined with oral rehydration solutions.
#### Immune Support and Recovery
Supporting the immune system is crucial for preventing and recovering from infections like cholera. NeoLife’s products that boost immune function can be beneficial:
- **Garlic Allium Complex**: Contains garlic and other allium vegetables known for their immune-boosting and antimicrobial properties.
- **Zinc**: An essential mineral that supports immune function and aids in recovery from infections.
### Community Education and Outreach
NeoLife has a history of involvement in community education programs, emphasizing the importance of hygiene, sanitation, and nutrition in preventing diseases like cholera. These efforts are crucial in reducing the incidence of cholera in vulnerable populations.
## Conclusion
NeoLife’s commitment to improving health through superior nutrition extends to addressing some of the world’s most pressing health challenges, including cancer, malaria, and cholera. While nutritional supplements alone cannot cure these diseases, they can play a vital role in prevention, supporting the immune system, and aiding recovery. Through a combination of scientifically formulated products, community education, and outreach programs, NeoLife continues to make a positive impact on global health.
By promoting balanced nutrition, supporting immune health, and advocating for holistic wellness, NeoLife contributes to the fight against cancer, malaria, and cholera, helping individuals lead healthier, more resilient lives.
# A Guide to Living a Happy and Long Life
## Table of Contents
1. **Introduction**
- Understanding the Importance of Longevity and Happiness
- How This Guide Can Help You Achieve Both
2. **Physical Health and Longevity**
- Importance of Exercise and Physical Activity
- Healthy Eating Habits for Longevity
- Regular Health Check-ups and Preventive Care
3. **Mental Well-being and Happiness**
- Strategies for Managing Stress
- Importance of Mental Health Awareness
- Practices for Cultivating a Positive Mindset
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4. **Social Connections and Longevity**
- Impact of Social Relationships on Longevity
- Building and Nurturing Meaningful Connections
- Community Engagement and Its Benefits
5. **Emotional Resilience and Happiness**
- Developing Emotional Intelligence
- Coping Strategies for Adversity
- Practicing Gratitude and Mindfulness
6. **Purpose and Meaning in Life**
- Finding Your Life's Purpose
- Setting Meaningful Goals
- Contribution to Others and Society
7. **Healthy Habits for a Long Life**
- Quality Sleep and Its Impact on Longevity
- Importance of Hydration
- Avoiding Harmful Substances and Habits
8. **Cognitive Health and Happiness**
- Brain Exercises and Mental Stimulation
- Importance of Continuous Learning
- Strategies for Maintaining Cognitive Function
9. **Environmental Factors**
- Creating a Healthy Living Environment
- Sustainable Practices for Longevity
- Connecting with Nature and Its Benefits
10. **Spirituality and Inner Peace**
- Role of Spirituality in Longevity
- Practices for Inner Peace and Tranquility
- Finding Balance in Life
11. **Conclusion**
- Recap of Key Strategies for a Happy and Long Life
- Final Thoughts and Encouragement
---
This guide aims to provide practical insights and actionable steps to help you enhance both your happiness and longevity. By focusing on physical health, mental well-being, social connections, purposeful living, healthy habits, cognitive health, environmental factors, and spirituality, you can achieve a more fulfilling and extended life. Let's explore these dimensions together to pave the way for a happier and longer journey ahead!
Welcome to Neolife.offersupermarket.com, your premier destination for a wide range of Neolife products designed to enhance your health and well-being. At Neolife.offersupermarket.com, we are committed to offering scientifically-backed nutritional supplements and wellness solutions that support a balanced lifestyle.
Discover our extensive selection of Neolife products, meticulously curated to meet your diverse health needs. Whether you're looking for high-quality vitamins, nourishing supplements, or natural health-enhancing formulas, Neolife.offersupermarket.com is your trusted source.
Our e-commerce store provides a user-friendly shopping experience, ensuring you can easily find and purchase the products that align with your health goals. From immunity-boosting supplements to products that promote heart health and overall vitality, each item at Neolife.offersupermarket.com is chosen for its effectiveness and quality.
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Join the community of health-conscious individuals who trust Neolife.offersupermarket.com for their nutritional needs. Whether you're starting a new wellness journey or maintaining a healthy lifestyle, our store is here to support you every step of the way.
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Certainly! Here's a word search puzzle using keywords related to Neolife:
```
N E O L I F E A H T R O F L A T E M I T R O V E P R O D U C T S
S E E N O H T L A E H E A L T H Y M E A L S S U P P L E M E N T
U S E S C I E N T I F I C A L L Y B A C K E D Q U A L I T Y Y E
T U R N B A C K T O L I F E B A L A N C E D N U T R I T I O N
M U L T I V I T A M I N S T E S T E D N U T R I E N T S U P P L
I E S N A T U R A L L Y D E V E L O P E D N O U R I S H E S K
```
**Words to find:**
1. NEOLIFE
2. HEALTHY
3. PRODUCTS
4. SCIENTIFICALLY
5. QUALITY
6. TURNBACKTOLIFE
7. BALANCED
8. NUTRITION
9. MULTIVITAMINS
10. TESTED
11. NUTRIENTS
12. SUPPLEMENTS
13. NATURALLY
14. DEVELOPED
15. NOURISHES
**Instructions:**
- Find the listed words in the grid.
- Words can be placed horizontally, vertically, diagonally, and backwards.
- Circle each word as you find it.
Enjoy solving the puzzle!
neolife Products Available For Purchase at neolife.offersupermarket.com
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neo-laxhttps://neolife.offersupermarket.com/product/fullmotion
### Understanding Mental Health, Suicide, and Depression
Mental health refers to our emotional, psychological, and social well-being. It affects how we think, feel, and act, influencing how we handle stress, relate to others, and make choices. When someone experiences poor mental health, it can lead to conditions such as depression.
**Depression** is a common mental health disorder characterized by persistent sadness and loss of interest in activities. It affects how you feel, think, and handle daily activities, impacting your ability to function normally.
**Suicide** is the tragic outcome of severe depression and other mental health issues. It occurs when individuals feel overwhelmed by emotional pain and see no other solution to their problems.https://neolife.offersupermarket.com/product/stresspack
### How Neolife Products Can Help with Mental Health
Neolife offers products designed to support mental well-being through natural ingredients and scientifically-backed formulations:
1. **Omega-3 Supplements**: Omega-3 fatty acids are crucial for brain health and can help alleviate symptoms of depression by supporting neurotransmitter function.neolife.offersupermarket.com/product/omega-salmon-oil
2. **Probiotics**: Gut health is linked to mental health. Probiotics promote a healthy gut microbiome, which can positively influence mood and reduce symptoms of anxiety and depression.
3. **Multivitamins**: Nutrient deficiencies can contribute to poor mental health. Neolife’s multivitamins provide essential vitamins and minerals that support overall well-being, including mental health.
4. **Herbal Supplements**: Ingredients like adaptogens (e.g., ashwagandha, rhodiola) and herbs (e.g., St. John’s Wort) have been shown to reduce stress, anxiety, and symptoms of depression.
5. **Protein Shakes and Bars**: Proper nutrition is vital for mental health. Neolife’s protein products provide balanced nutrition that supports mood regulation and overall mental well-being.https://neolife.offersupermarket.com/product/healthymilkshake
### Conclusion
Maintaining good mental health is essential for a fulfilling life. O products offer natural solutions to support mental well-being, complementing healthy lifestyle choices and professional mental health care. By addressing nutritional needs and promoting overall wellness, Neolife contributes to a holistic approach to mental health management.
! Here's a detailed guide on how NeoLife products can support mental health:
---
### Introduction to NeoLife Products for Mental Health
Maintaining good mental health is crucial for overall well-being and quality of life. NeoLife offers a range of nutritional supplements that can complement a healthy lifestyle and support mental health. This comprehensive guide explores the benefits of NeoLife products and their potential impact on mental well-being.
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### Section 1: Understanding Mental Health
1. **Importance of Mental Health**
- Mental health encompasses emotional, psychological, and social well-being.
- Good mental health enables individuals to cope with stress, maintain relationships, and lead fulfilling lives.
2. **Factors Affecting Mental Health**
- **Nutrition:** Diet plays a role in brain function and mood regulation.
- **Physical Activity:** Exercise promotes mental clarity and reduces stress.
- **Sleep:** Adequate sleep supports cognitive function and emotional resilience.
- **Stress Management:** Techniques like mindfulness and relaxation can improve mental health.
### Section 2: NeoLife Products for Mental Health Support
1. **Omega-3 Supplements (NeoLife Salmon Oil Plus)**
- **Benefits:** Omega-3 fatty acids (EPA and DHA) support brain function and mood regulation.
- **Usage:** Take NeoLife Salmon Oil Plus daily to promote cognitive health and emotional well-being.
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2. **Multivitamins and Minerals (Pro Vitality+)**
- **Benefits:** Comprehensive nutrition with vitamins, minerals, and Tre-en-en for overall health.
- **Usage:** Support mental clarity and energy levels with Pro Vitality+.
3. **Antioxidants (Carotenoid Complex)**
- **Benefits:** Carotenoids like lutein and beta-carotene protect brain cells from oxidative stress.
- **Usage:** Promote brain health and protect against cognitive decline.
4. **Probiotics and Digestive Health (NeoLife Acidophilus Plus)**
- **Benefits:** Gut-brain connection supports mood and mental clarity.
- **Usage:** Maintain gut health with NeoLife Acidophilus Plus for overall well-being.
5. **Vitamin D (Chelated Cal-Mag with Vitamin D3)**
- **Benefits:** Vitamin D supports neurotransmitter function and mood regulation.
- **Usage:** Ensure adequate Vitamin D intake for mental health support.
### Section 3: Lifestyle Factors and Mental Health
1. **Nutrition and Diet**
- **Balanced Diet:** Include fruits, vegetables, whole grains, lean proteins, and healthy fats to support brain function.
- **Hydration:** Drink plenty of water to maintain cognitive function and mood stability.
2. **Physical Activity**
- **Exercise Benefits:** Boost mood through endorphin release and reduce stress levels.
- **Routine:** Incorporate regular exercise into your routine for long-term mental health benefits.
3. **Sleep Hygiene**
- **Quality Sleep:** Aim for 7-9 hours of sleep per night to support cognitive function and emotional resilience.
- **Routine:** Establish a consistent sleep schedule and create a relaxing bedtime routine.
4. **Stress Management**
- **Techniques:** Practice mindfulness, meditation, deep breathing, or yoga to reduce stress levels.
- **Support Systems:** Seek social support and engage in activities that promote relaxation and enjoyment.
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### Section 4: Incorporating NeoLife Products into Your Routine
1. **Consultation and Guidance**
- **Distributor Support:** Consult with a NeoLife distributor for personalized recommendations based on your health goals.
- **Product Usage:** Follow recommended dosages and integrate NeoLife products into your daily routine for optimal mental health support.
### Section 5: Research and Evidence
1. **Scientific Studies**
- **Omega-3 Fatty Acids:** Research supports the role of EPA and DHA in improving mood disorders such as depression and anxiety.
- **Vitamins and Minerals:** Studies indicate that deficiencies in certain nutrients can affect mental health outcomes.
### Conclusion
NeoLife products can play a valuable role in supporting mental health when used as part of a holistic approach that includes nutrition, physical activity, sleep, and stress management. By prioritizing mental well-being and incorporating NeoLife supplements into your routine, you can enhance cognitive function, mood regulation, and overall quality of life.
### References
- Include citations and sources used to compile information on NeoLife products and their benefits for mental health.
---
Losing weight with NeoLife products is straightforward when you follow these simple steps:
### Step-by-Step Guide to Losing Weight with NeoLife Products
1. **NeoLifeShake for Meal Replacement**
- **What it does:** NeoLifeShake provides balanced nutrition with protein, vitamins, and fiber.
- **How to use:** Replace one or two meals a day with NeoLifeShake to cut down on calories while still getting essential nutrients.
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2. **Pro Vitality+ for Daily Nutrition**
- **What it does:** Pro Vitality+ gives you vitamins, minerals, and special fats (like Tre-en-en) for overall health.
- **How to use:** Take Pro Vitality+ every day to fill in any nutritional gaps and keep your energy levels up.
3. **NeoLifeTea for Energy and Metabolism**
- **What it does:** NeoLifeTea boosts your metabolism and gives you energy with natural ingredients like green tea.
- **How to use:** Drink NeoLifeTea daily to help burn more calories and stay energized throughout the day.
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4. **NeoLifeBar for Healthy Snacking**
- **What it does:** NeoLifeBar is a handy snack that's high in protein and fiber, keeping you full between meals.
- **How to use:** Use NeoLifeBar as a healthy snack option to satisfy cravings without derailing your weight loss efforts.
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### Tips for Success
- **Consistency:** Stick to your NeoLife routine daily for best results.
- **Healthy Eating:** Choose balanced meals with lots of fruits, veggies, lean proteins, and whole grains.
- **Exercise:** Stay active with regular workouts to burn calories and improve your fitness.
### Safety Notes
- **Consultation:** Talk to your doctor before starting any weight loss plan, especially if you have health issues or take medications.
- **Monitoring:** Keep track of your progress and adjust your NeoLife product usage as needed.
By combining NeoLife products with healthy eating and exercise, you can effectively lose weight and improve your overall health.
Losing weight effectively and sustainably involves a combination of healthy eating habits, regular physical activity, and lifestyle changes. Here’s a comprehensive guide on how to lose weight:
---
### Introduction to Weight Loss
Losing weight is a goal for many individuals seeking to improve their health and well-being. While the process can vary depending on individual circumstances, understanding the fundamentals of weight loss is crucial for achieving sustainable results.
### Section 1: Understanding Weight Loss
1. **Basics of Weight Loss**
- Weight loss occurs when there is a calorie deficit, meaning you consume fewer calories than your body needs to maintain its current weight.
- 1 pound of body weight is roughly equivalent to 3,500 calories. To lose 1 pound per week, you need a deficit of about 500 calories per day.
2. **Factors Affecting Weight Loss**
- **Metabolism:** Your metabolic rate influences how quickly you burn calories.
- **Genetics:** Genetic factors can affect weight loss and body composition.
- **Lifestyle:** Habits such as diet, physical activity, sleep, and stress management play critical roles.
### Section 2: Creating a Weight Loss Plan
1. **Setting Realistic Goals**
- Establish achievable goals based on your current weight, health status, and lifestyle.
- Aim for gradual weight loss (1-2 pounds per week) to promote long-term success.
2. **Nutrition for Weight Loss**
- **Calorie Deficit:** Calculate your daily calorie needs and create a deficit through diet.
- **Balanced Diet:** Focus on whole foods, lean proteins, fruits, vegetables, whole grains, and healthy fats.
- **Portion Control:** Monitor serving sizes to manage calorie intake effectively.
3. **Physical Activity**
- **Types of Exercise:** Incorporate aerobic activities (walking, jogging, swimming) and strength training to build muscle and burn calories.
- **Frequency and Duration:** Aim for at least 150 minutes of moderate-intensity exercise per week, plus muscle-strengthening activities on two or more days.
4. **Behavioral Changes**
- **Mindful Eating:** Pay attention to hunger cues and avoid emotional eating.
- **Food Journaling:** Track food intake to identify patterns and make adjustments.
- **Sleep and Stress Management:** Prioritize adequate sleep and manage stress to support weight loss efforts.
### Section 3: Strategies for Success
1. **Support System**
- Engage with friends, family, or support groups for encouragement and accountability.
- Consider working with a registered dietitian or personal trainer for personalized guidance.
2. **Monitoring Progress**
- Track weight loss using measurements, body composition analysis, or progress photos.
- Celebrate milestones and adjust goals as needed based on progress.
3. **Maintaining Weight Loss**
- Transition to a balanced diet that supports weight maintenance.
- Continue regular physical activity and monitor habits to prevent weight regain.
### Section 4: Potential Challenges and Solutions
1. **Plateaus**
- Adjust calorie intake or exercise routine to overcome weight loss plateaus.
- Evaluate habits and make changes to break through barriers.
2. **Social and Environmental Factors**
- Navigate social situations and environments that may influence eating habits.
- Plan ahead and make healthier choices when dining out or attending gatherings.
### Section 5: Health Considerations and Safety
1. **Consultation with Healthcare Professionals**
- Seek medical advice before starting any weight loss program, especially if you have underlying health conditions or are taking medications.
- Monitor health metrics such as blood pressure, cholesterol levels, and blood sugar levels during weight loss.
2. **Healthy Weight Loss vs. Fad Diets**
- Avoid quick-fix diets or supplements promising rapid weight loss.
- Focus on sustainable habits that promote overall health and well-being.
### Conclusion
Achieving and maintaining a healthy weight involves adopting a balanced approach to nutrition, physical activity, and lifestyle. By understanding the principles of weight loss, setting realistic goals, and making sustainable changes, individuals can successfully manage their weight and improve their quality of life.
##
---
| **Benefits of Tre-en-en** https://neolife.offersupermarket.com/product/tre-en-en |
|----------------------------------------------------------------|
| **1. Cellular Nutrition:** Provides essential lipids and sterols to support cellular membrane function and efficiency. |https://neolife.offersupermarket.com/product/tre-en-en
| **2. Enhances Energy:** Helps improve cellular energy production and utilization. |
| **3. Supports Cardiovascular Health:** Promotes healthy circulation and cardiovascular function. |
| **4. Boosts Immunity:** Supports immune system function by promoting healthy cell membranes. |
| **5. Promotes Healthy Skin:** Supports skin health and appearance by nourishing cells from within. |
| **6. Improves Overall Vitality:** Helps maintain overall vitality and well-being through cellular support. |
---
**Note:** Tre-en-en is formulated to support cellular health and function, which can have wide-ranging benefits for various aspects of health and well-being. Adjust the information based on specific scientific studies or testimonials related to Tre-en-en from NeoLife.
---
**Word Finder Game: Health Words Edition**
**Objective:** Find as many health-related words as you can from the grid below.
**Instructions:** Look horizontally, vertically, and diagonally to find the words. When you find a word, circle it or mark it off. The words can be forwards or backwards.
```
R S T L I F E S T Y L E A
A N A E R O B I C T D F H
U H Y G I E N E C R H S I
F O O D Q U A L I T Y G E
I M M U N I T Y H B S G D
T S U N S C R E E N U T A
R E L A X A T I O N R U I
E E R A P Y M E D I T A T
D I E T R E S T T K R C Y
```
**List of Health Words:**
- Lifestyle
- Aerobic
- Hygiene
- Food
- Quality
- Immunity
- Sunscreen
- Relaxation
- Therapy
- Diet
- Rest
- Meditation
**Scoring:** Count how many words you find correctly. Challenge yourself to find them all!
---
### Tre-en-en: Comprehensive Notes
**Introduction to Tre-en-en**
Tre-en-en is a whole-grain concentrate supplement developed by Neolife. It is designed to support cellular nutrition by providing essential lipids and sterols, which are crucial for cell membrane function. Tre-en-en aims to enhance overall health by ensuring cells receive the nutrients they need to operate efficiently.
### History and Development
#### Origin of Tre-en-en
Tre-en-en was introduced by Neolife in 1958, making it one of the company's flagship products. It was the first nutritional supplement to provide a scientifically formulated blend of whole-grain concentrates, specifically targeting cell membrane health.
#### Scientific Foundation
The development of Tre-en-en was based on research indicating that certain essential lipids and sterols found in whole grains are critical for optimal cell function. The product was created to address the nutritional gap left by modern food processing, which often strips away these vital nutrients.
### Composition of Tre-en-en
Tre-en-en is formulated with extracts from wheat, rice, and soybeans, each providing a unique profile of lipids and sterols:https://neolife.offersupermarket.com/product/tre-en-en
#### Wheat Germ Oil
- **Benefits:** Rich in octacosanol, which supports physical endurance and performance.
- **Nutritional Profile:** Contains essential fatty acids, vitamin E, and other antioxidants that protect cells from oxidative stress.
#### Rice Bran Oil
- **Benefits:** High in gamma-oryzanol and phytosterols, which help maintain healthy cholesterol levels and support hormonal balance.
- **Nutritional Profile:** Provides a balanced spectrum of lipids, including omega-6 fatty acids.
#### Soybean Oil
- **Benefits:** Contains lecithin, which supports brain function and liver health.
- **Nutritional Profile:** A rich source of essential fatty acids, including omega-3 and omega-6.
### Mechanism of Action
Tre-en-en works by enhancing the function of cell membranes. Healthy cell membranes are essential for nutrient absorption, waste removal, and overall cellular communication. The lipids and sterols in Tre-en-en help to:
1. **Improve Cell Membrane Structure:** They ensure that cell membranes remain fluid and flexible, allowing for efficient transport of nutrients and waste.
2. **Enhance Nutrient Utilization:** By improving cell membrane permeability, cells can better absorb nutrients from the bloodstream.
3. **Support Hormonal Function:** Sterols serve as precursors for hormones, aiding in the regulation of various bodily functions.
4. **Boost Energy Levels:** Improved cellular function translates to better energy production at the cellular level, enhancing overall vitality.
### Health Benefits of Tre-en-en
#### Enhanced Cellular Nutrition
By providing essential lipids and sterols, Tre-en-en ensures that cells receive the nutrients they need to function optimally. This can lead to improved overall health and vitality.
#### Improved Immune Function
Healthy cell membranes are crucial for immune cell function. Tre-en-en supports the immune system by ensuring immune cells can effectively communicate and respond to threats.
#### Cardiovascular Health
The lipids and sterols in Tre-en-en help maintain healthy cholesterol levels, supporting overall cardiovascular health. Phytosterols, in particular, are known to reduce LDL cholesterol levels.https://neolife.offersupermarket.com/product/tre-en-en
#### Hormonal Balance
Sterols in Tre-en-en serve as precursors for hormones, helping to maintain hormonal balance. This can be beneficial for conditions like premenstrual syndrome (PMS) and menopause.
#### Enhanced Energy Levels
Improved cellular function can lead to increased energy production. Users often report feeling more energetic and less fatigued when taking Tre-en-en regularly.
#### Cognitive Function
The lipids in Tre-en-en, especially lecithin, support brain health and cognitive function. This can lead to improved memory, focus, and overall mental clarity.
### Scientific Research and Evidence
#### Early Studies
Early research on Tre-en-en focused on the role of lipids and sterols in cellular nutrition. Studies demonstrated that these nutrients are essential for maintaining healthy cell membranes and overall cellular function.
#### Clinical Trials
Several clinical trials have been conducted to evaluate the efficacy of Tre-en-en. These studies have shown that Tre-en-en supplementation can lead to improvements in various health markers, including cholesterol levels, immune function, and energy levels.
#### Ongoing Research
Neolife continues to invest in research to further understand the benefits of Tre-en-en. Current studies are exploring its potential role in supporting healthy aging, cognitive function, and overall metabolic health.
### Usage and Dosage
#### Recommended Dosage
The recommended dosage of Tre-en-en is typically 1 to 3 capsules per day, taken with meals. It is important to follow the dosage instructions provided on the product label or as advised by a healthcare professional.
#### Usage Guidelines
- **Consistency:** For best results, Tre-en-en should be taken consistently as part of a daily routine.
- **With Meals:** Taking Tre-en-en with meals enhances the absorption of its nutrients.
- **Hydration:** Adequate hydration is important for optimal cellular function and nutrient absorption.
### Potential Side Effects and Safety
#### General Safety
Tre-en-en is considered safe for most individuals when taken as directed. It is formulated with natural ingredients and does not contain artificial additives or preservatives.
#### Potential Side Effects
While side effects are rare, some individuals may experience mild digestive discomfort when first starting Tre-en-en. This can include symptoms like bloating or gas, which typically subside as the body adjusts to the supplement.
#### Precautions
- **Allergies:** Individuals with allergies to wheat, rice, or soy should consult a healthcare professional before taking Tre-en-en.
- **Medical Conditions:** Those with pre-existing medical conditions or who are taking other medications should seek medical advice before starting any new supplement.
### Comparisons with Other Supplements
#### Unique Selling Points
Tre-en-en stands out from other supplements due to its unique blend of whole-grain concentrates, providing a comprehensive profile of essential lipids and sterols. Unlike many supplements that focus solely on vitamins and minerals, Tre-en-en addresses the often-overlooked need for cellular lipids.
#### Similar Products
While there are other supplements that provide essential fatty acids or plant sterols, Tre-en-en's formulation is unique in its focus on whole-grain extracts and the specific combination of wheat, rice, and soybean oils.
### Testimonials and Case Studies
#### User Experiences
Many users have reported significant health benefits from taking Tre-en-en, including increased energy levels, improved immune function, and better overall well-being. Testimonials often highlight the supplement's role in enhancing daily vitality and supporting long-term health.
#### Case Studies
Neolife has documented several case studies showcasing the impact of Tre-en-en on individuals with specific health conditions. These case studies provide valuable insights into the supplement's effectiveness and real-world applications.
### Market Presence and Availability
#### Global Reach
Tre-en-en is available in numerous countries worldwide, reflecting Neolife's extensive global reach. The product can be purchased through Neolife's network of independent distributors or online.
#### Distribution Channels
Neolife utilizes a direct selling model, allowing independent distributors to market and sell Tre-en-en. This model provides a personalized approach to customer service and product education.
### Pricing and Value
#### Cost
The cost of Tre-en-en can vary depending on the region and purchasing method. While it may be more expensive than some generic supplements, its unique formulation and quality ingredients offer significant value.
#### Value Proposition
Tre-en-en provides a unique combination of essential lipids and sterols, supporting comprehensive cellular nutrition. Its scientifically-backed formulation and numerous health benefits make it a valuable addition to a daily health regimen.
### Future Prospects and Innovations
#### Ongoing Development
Neolife continues to innovate and develop new products to complement Tre-en-en. Future formulations may include enhanced versions or new delivery methods to improve convenience and efficacy.
#### Research and Expansion
Neolife is committed to ongoing research to further validate the benefits of Tre-en-en and explore new applications. The company's focus on scientific advancement ensures that Tre-en-en remains a leading product in the nutritional supplement market.
### Conclusion
Tre-en-en is a pioneering nutritional supplement that provides essential lipids and sterols from whole-grain concentrates. Its unique formulation supports cellular health, enhances energy levels, and promotes overall well-being. With a strong scientific foundation, extensive research, and numerous user testimonials, Tre-en-en stands out as a valuable tool for those seeking to improve their health through better cellular nutrition. Neolife's commitment to quality and innovation ensures that Tre-en-en will continue to be a trusted and effective supplement for years to come.
NeoLife is a company ownfor its nutritional products and supplements. Here are a few questions:
1. **What does NeoLife specialize in?*
- A) Cosmetics
- B) Nutritional products
- C) Electronics
- D) Clothing
2. **Where was NeoLife founded?**
- A) United States
- B) United Kingdom
- C) Canada
- D) Germany
3. **Which of the following is a popular NeoLife product category?**
- A) Exercise equipment
- B) Household appliances
- C) Weight loss supplements
- D) Pet supplies
4. **True or False: NeoLife emphasizes the use of natural ingredients in its products.**
5. **What is the NeoLife motto?**
- A) "Healthy living for everyone"
- B) "Live well, be well"
- C) "Nutrition for life"
- D) "Wellness starts here"
Feel free to answer these questions, and I'll provide feedback on your responses!
Tre-en-en is a product offered by NeoLife, known for its unique formulation of whole grain concentrates. Here are some benefits associated with Tre-en-en:
1. **Cellular Nutrition**: Tre-en-en provides essential lipids and sterols to support cellular membrane function, which can enhance overall cellular health and function.
2. **Energy Production**: By supporting cellular membrane function, Tre-en-en helps cells function more efficiently, potentially leading to improved energy production within the body.
3. **Nutrient Absorption**: It can enhance nutrient absorption by promoting healthy cellular membranes, which are essential for transporting nutrients into cells.
4. **Overall Health**: Users often report improved vitality and overall well-being due to better cellular function and nutrient absorption.
These benefits make Tre-en-en a popular choice among those looking to support their cellular health and overall vitality.
Fun Neolife And Health Quiz
Certainly! Here's a health quiz with answers provided:
1. **Which of the following nutrients is essential for healthy vision?**
- A) Vitamin C
- B) Vitamin D
- C) Vitamin A
- D) Vitamin K
**Answer: C) Vitamin A**
2. **What is the normal resting heart rate for adults?**
- A) 50-70 beats per minute
- B) 80-100 beats per minute
- C) 110-130 beats per minute
- D) 30-40 beats per minute
**Answer: A) 50-70 beats per minute**
3. **Which food is a good source of omega-3 fatty acids?**
- A) Beef
- B) Salmon
- C) Chicken
- D) Pork
**Answer: B) Salmon**
4. **Which type of exercise primarily improves flexibility?**
- A) Running
- B) Cycling
- C) Yoga
- D) Weightlifting
**Answer: C) Yoga**
5. **What is the recommended amount of physical activity per week for adults, according to guidelines?**
- A) 30 minutes
- B) 60 minutes
- C) 150 minutes
- D) 300 minutes
**Answer: C) 150 minutes**
6. **Which organ is primarily responsible for detoxifying the body?**
- A) Liver
- B) Kidneys
- C) Lungs
- D) Heart
**Answer: A) Liver**
7. **What is the best way to reduce the risk of spreading infections?**
- A) Washing hands frequently
- B) Taking antibiotics daily
- C) Avoiding vaccinations
- D) Sharing personal items
**Answer: A) Washing hands frequently**
8. **Which of the following is a symptom of a heart attack?**
- A) Sudden blurred vision
- B) Persistent headache
- C) Chest pain or discomfort
- D) Muscle cramps
**Answer: C) Chest pain or discomfort**
9. **What is the recommended daily intake of fiber for adults?**
- A) 5 grams
- B) 10 grams
- C) 25 grams
- D) 50 grams
**Answer: C) 25 grams**
10. **Which habit contributes to good oral health?**
- A) Brushing teeth once a week
- B) Eating sugary snacks frequently
- C) Flossing daily
- D) Drinking sugary beverages before bed
**Answer: C) Flossing daily**
### Comprehensive Notes on NeoLife
#### Overview
NeoLife is a global company focused on providing high-quality nutrition products. The company's mission is to improve lives by offering scientifically researched and tested products that support optimal health.
#### History and Background
1. **Foundation**: NeoLife was founded in 1958 by Jerry Brassfield. Initially, the company operated under the name Golden Products and later became known as GNLD International before rebranding to NeoLife.
2. **Mission**: The company’s mission is to make a positive difference in people’s lives by providing the highest quality nutrition products backed by science.
3. **Global Presence**: NeoLife operates in over 50 countries, demonstrating its broad international reach and appeal.
#### Product Categories
NeoLife offers a wide range of products across several categories:
1. **Nutritional Supplements**:
- **Vitamins and Minerals**: Essential vitamins and minerals to support overall health.
- **Omega-3 Supplements**: Products like Salmon Oil Plus for heart and brain health.https://neolife.offersupermarket.com/product/tre-en-en
- **Pro Vitality**: A daily pack combining essential nutrients.
2. **Weight Management**:
- **NeoLifeShake**: A meal replacement shake designed to support weight loss and management.https://neolife.offersupermarket.com/product/healthymilkshake
- **GR2 Control**: A program focusing on balanced, glycemic-responsive nutrition.
3. **Sport Performance**:
- **Sport Performance Protein**: Whey-based protein blend to support muscle building and recovery.
- **Recovery Products**: Supplements designed to aid post-exercise recovery.
4. **Herbal Alternatives**:
- **Herbal Products**: Items like NeoLifeTea and NeoLifeBar for natural energy and health benefits.
5. **Personal Care**:
- **Nutriance Organic**: A line of skin care products made with organic ingredients.
6. **Home Care**:
- **Golden Home Care**: A range of eco-friendly cleaning products.
#### Key Products and Ingredients
1. **NeoLife Aloe Vera Plus**:
- **Aloe Vera Juice**: Supports gastrointestinal health.
- **Herbal Tea Blend**: Includes ginseng and chamomile for energy and relaxation.
- **Vitamin C**: Provides 170% of the daily value to support immune health.
2. **Pro Vitality Pack**:
- **Tre-en-en® Grain Concentrates**: Supports cell membrane function.
- **Carotenoid Complex**: Antioxidants for immune support.https://neolife.offersupermarket.com/product/tre-en-en
- **Omega-3 Salmon Oil Plus**: Heart and brain health.
- **Essential Vitamins & Minerals**: Comprehensive daily nutrition.
3. **NeoLifeShake**:https://neolife.offersupermarket.com/product/healthymilkshake
- **Protein Blend**: Whey and soy proteins for muscle support.
- **Vitamins and Minerals**: Ensures balanced nutrition.
- **Glycemic Edge Technology**: Helps maintain stable blood sugar levels.
#### Scientific Research and Development
1. **Scientific Advisory Board (SAB)**: A team of renowned scientists and nutrition experts who guide product development.
2. **Clinical Studies**: Many NeoLife products are backed by peer-reviewed clinical studies that validate their efficacy and safety.
3. **High-Quality Ingredients**: Commitment to using non-GMO ingredients, and ensuring all products are free from artificial colors, flavors, and preservatives.
#### Business Model
1. **Direct Selling**: NeoLife operates primarily through a network marketing model, empowering individuals to become distributors and build their own businesses.
2. **Distributor Support**: Provides extensive training, resources, and support to help distributors succeed.
3. **Incentives and Rewards**: Offers various incentives, including bonuses, trips, and recognition programs for high-performing distributors.
#### Health and Wellness Philosophy
1. **Holistic Approach**: Emphasizes the importance of balanced nutrition, regular exercise, and mental well-being.
2. **Preventive Health**: Focuses on prevention through nutrition to maintain optimal health and avoid chronic diseases.
3. **Community and Education**: Engages in community outreach and educational initiatives to promote health and wellness.
#### Corporate Social Responsibility
1. **Environmental Sustainability**: Committed to eco-friendly practices in product formulation and packaging.
2. **Philanthropy**: Supports various charitable organizations and initiatives aimed at improving health and wellness globally.
3. **Ethical Practices**: Adheres to high ethical standards in all business operations.
#### Customer Testimonials and Reviews
1. **Positive Feedback**: Many customers report significant health improvements and satisfaction with NeoLife products.
2. **Success Stories**: Testimonials often highlight weight loss, increased energy, improved digestion, and overall better health.
#### Challenges and Criticisms
1. **Price Point**: Some consumers find NeoLife products to be on the pricier side compared to other brands.
2. **Skepticism Towards MLM**: The multi-level marketing business model is sometimes met with skepticism.
3. **Market Competition**: Faces competition from other health and wellness brands that offer similar products.
#### Future Outlook
1. **Innovation**: Continuously invests in research and development to introduce new and improved products.
2. **Expansion**: Aims to expand its global footprint and reach more consumers worldwide.
3. **Health Trends**: Plans to align with emerging health trends and consumer demands, such as plant-based nutrition and personalized health solutions.
### Summary
NeoLife stands out for its commitment to quality, scientific backing, and a holistic approach to health and wellness. While it faces challenges common to the industry, it continues to grow and innovate, maintaining a strong presence in the global nutrition market.
For more detailed information about NeoLife and its products, you can visit their official website or consult with a NeoLife distributor.
NeoLife Aloe Vera products, particularly Aloe Vera Plus, are formulated to harness the numerous benefits of aloe vera combined with other natural ingredients to support overall health and wellness.
### Key Ingredients:
1. **Aloe Vera Juice**: The primary ingredient is pure aloe vera juice, sourced through a "gel only" filleting process that preserves aloe polysaccharides for maximum efficacy.
2. **Herbal Tea Blend**: This includes ginseng (Eleuthero) for energy, chamomile and passionflower to promote relaxation and reduce stress.
3. **Electrolytes**: Potassium and magnesium are included to support metabolic processes, particularly for cardiovascular and nervous system health.
4. **Vitamin C**: Each serving provides 170% of the daily value for vitamin C, an antioxidant that supports immune health, skin tone, and overall vitality.
5. **Natural Sweeteners**: The product is sweetened with fructose, which provides a "glycemic edge" for sustained energy without causing insulin spikes, making it suitable for people monitoring their blood sugar levels.
### Benefits:
- **Digestive Health**: Aloe Vera Plus is known for soothing the digestive system, alleviating discomfort caused by stress-induced digestive issues.
- **Energy and Relaxation**: The combination of ginseng and chamomile in the herbal tea blend provides a balanced effect of energy and relaxation.
- **Immune Support**: The high vitamin C content aids in bolstering the immune system.
- **Low Calorie**: With only 16 calories per 2-ounce serving, it is a low-calorie option for those looking to maintain or lose weight while still benefiting from its nutritional properties.
### Usage:
- Recommended daily intake is between 50-120 ml, and it is best enjoyed chilled. It is advised not to exceed the recommended dosage and to store the product in a cool place after opening.
Overall, NeoLife Aloe Vera Plus is designed to be a refreshing and beneficial addition to your daily routine, helping to manage stress, support digestion, and provide essential nutrients for overall well-being【https://neolife.offersupermarket.com/product/aloe-vera
! Here are notes for 30 products suitable for pregnancy:
1. **Prenatal Vitamins**: Essential for supporting the health of both mother and baby, providing key nutrients like folic acid, iron, and calcium.
https://neolife.offersupermarket.com/product/allnaturalfiber
2. **Maternity Clothing**: Comfortable and stylish apparel designed to accommodate a growing belly, including tops, bottoms, dresses, and bras.https://oldnavy.gap.com/browse/division.do?cid=5758
3. **Body Pillows**: Provide support for the back, hips, and abdomen, promoting better sleep and relieving discomfort during pregnancy.
https://www.nytimes.com/wirecutter/reviews/best-body-pillow/
4. **Stretch Mark Creams/Oils**: Help moisturize the skin and reduce the appearance of stretch marks caused by the stretching of the belly.https://www.google.com/amp/s/www.nbcnews.com/select/amp/rcna156737
5. **Pregnancy Books**: Informative resources covering pregnancy, childbirth, and newborn care, offering guidance and reassurance to expecting mothers.https://www.thebump.com/a/pregnancy-books
6. **Maternity Support Belt**: Provides abdominal and lower back support, reducing strain and discomfort as the belly grows.
7. **Pregnancy Journal**: Allows mothers to document their pregnancy journey, emotions, and milestones, creating a keepsake for years to come.
8. **Nausea Relief Products**: Including ginger candies, acupressure wristbands, and over-the-counter medications approved by healthcare providers.
9. **Comfortable Shoes**: Supportive footwear to accommodate swollen feet and provide stability, reducing the risk of falls and discomfort.http://Nike.com
10. **Water Bottle with Straw**: Encourages hydration, which is crucial during pregnancy, and makes it easier for mothers to drink enough water throughout the day.
11. **Pregnancy Pillow**: Provides support for the belly, back, and knees, improving sleep quality and reducing pregnancy-related discomfort.
12. **Breastfeeding Pillow**: Supports the baby during nursing sessions, promoting proper positioning and reducing strain on the mother's back and arms.
13. **Prenatal Yoga DVD/Classes**: Gentle exercises and stretches tailored to pregnant women, promoting relaxation, flexibility, and overall well-being.
14. **Labor and Delivery Gown**: Comfortable and stylish gowns designed specifically for childbirth, offering easy access for medical procedures.
15. **Compression Socks**: Help prevent swelling and improve circulation in the legs and feet, which is common during pregnancy.
16. **Fetal Doppler Monitor**: Allows mothers to listen to their baby's heartbeat at home, providing reassurance and bonding opportunities.
17. **Pregnancy-Safe Skincare Products**: Gentle cleansers, moisturizers, and sunscreen formulated without harmful ingredients like retinoids or salicylic acid.
18. **Birth Ball**: Promotes proper posture and relaxation during pregnancy and can be used for exercises to prepare for labor and childbirth.
19. **Maternity Belt**: Offers support and relief for the pelvis and lower back, particularly helpful for women experiencing pelvic girdle pain or SPD.
20. **Healthy Snacks**: Nutritious options like fruits, nuts, and yogurt to satisfy cravings and maintain energy levels throughout the day.
https://neolife.offersupermarket.com/details/p6908624_20256811.aspx
21. **Perineal Massage Oil**: Helps prepare the perineum for childbirth by moisturizing and increasing flexibility, potentially reducing the risk of tearing.
22. **Postpartum Belly Wrap**: Provides support to the abdomen and helps shrink the uterus back to its pre-pregnancy size after childbirth.
23. **Maternity Underwear**: Comfortable underwear designed to accommodate a growing belly and provide support during pregnancy and postpartum.
24. **Breast Pads**: Absorbent pads to manage leakage of colostrum or breast milk during pregnancy and breastfeeding.
25. **Pregnancy-Safe Essential Oils**: Relaxing scents like lavender or chamomile, used in aromatherapy to promote relaxation and alleviate stress.
26. **Gentle Stool Softener**: Helps prevent or relieve constipation, a common issue during pregnancy due to hormonal changes and pressure on the digestive system.
https://neolife.offersupermarket.com/product/allnaturalfiber
27. **Childbirth Education Classes**: Informative courses covering topics such as childbirth techniques, pain management options, and newborn care.
28. **Portable Pregnancy Seat Belt Adjuster**: Ensures proper positioning of the seat belt over the belly, reducing the risk of injury in case of a car accident.
https://shop.saferide4kids.com/products/tummy-shield
29. **Pregnancy Workout DVDs/Classes**: Safe exercises tailored to pregnant women, promoting strength, flexibility, and overall fitness.
https://www.childbirthgraphics.com/71418-Understanding-Pregnancy-DVD
30. **Breast Pump**: Allows mothers to express breast milk for feeding their baby when they are unable to breastfeed directly, providing flexibility and convenience.
https://thebreastpumpstore.com/collections/all
These products can help expecting mothers navigate the journey of pregnancy with comfort, support, and peace of mind.
Living a healthy life involves various factors, including nutrition, exercise, sleep, stress management, and overall well-being. Here are some notes on products that can contribute to a healthy lifestyle:
1. **Nutritional Supplements**:
- Multivitamins: Provide essential vitamins and minerals to support overall health and fill nutritional gaps in the diet.
- Omega-3 Fatty Acids: Support heart health, brain function, and joint health.https://neolife.offersupermarket.com/product/omega-salmon-oil
- Probiotics: Promote gut health and strengthen the immune system.https://neolife.offersupermarket.com/product/betagard
- Antioxidants: Help combat oxidative stress and reduce the risk of chronic diseases.
https://neolife.offersupermarket.com/product/stresspack
2. **Healthy Food Options**:
- Whole Foods: Include plenty of fruits, vegetables, whole grains, lean proteins, and healthy fats in your diet.
- Organic Products: Opt for organic produce and foods to minimize exposure to pesticides and other harmful chemicals.
- Superfoods: Incorporate nutrient-dense foods like berries, leafy greens, nuts, seeds, and fatty fish into your diet for added health benefits.
3. **Fitness Equipment and Gear**:
- Exercise Mat: Provides cushioning and support for various floor exercises and yoga poses.
https://www.amazon.com/exercise-mats-gym-mats/b?ie=UTF8&node=3407941
- Resistance Bands: Offer a portable and versatile way to strength train and improve flexibility.
- Running Shoes: Provide support, stability, and cushioning for running and other physical activities.
https://www.nike.com/w/running-shoes-37v7jzy7ok
- Fitness Tracker: Monitors daily activity levels, heart rate, sleep quality, and other health metrics to help you stay on track with your fitness goals.
4. **Sleep Aids**:
- Mattress and Pillows: Choose a comfortable and supportive mattress and pillows to promote better sleep posture and quality.
https://www.amazon.com/sleep-aid/s?k=sleep+aid
- Sleep Masks and Earplugs: Block out light and noise for a more restful sleep environment.
- White Noise Machines: Create a soothing background noise to mask disruptive sounds and promote relaxation.
https://www.bestbuy.com/site/shop/best-sound-machines
5. **Stress Relief Products**:
- Aromatherapy Essential Oils: Use calming scents like lavender, chamomile, and eucalyptus to reduce stress and promote relaxation.https://elsieorganics.com/product/lavender-buds-dried/
- Stress Balls: Provide a simple and effective way to relieve tension and improve hand strength.https://www.aliexpress.com/w/wholesale-stress-ball.html
- Meditation Apps: Offer guided meditation sessions, breathing exercises, and mindfulness practices to help manage stress and anxiety.
6. **Hydration Products**:
- Water Bottles: Carry a reusable water bottle to stay hydrated throughout the day and avoid sugary beverages.
https://www.nytimes.com/wirecutter/reviews/best-water-bottle/
- Electrolyte Drinks: Replenish electrolytes lost through sweat during exercise or hot weather to maintain proper hydration levels.
7. **Safety and Wellness Accessories**:
- Sunscreen: Protects the skin from harmful UV rays and reduces the risk of sunburn, skin cancer, and premature aging.https://allure.com.ng/product-category/face/sun-protection/sunscreen/
- First Aid Kit: Includes essential supplies for treating minor injuries and emergencies at home or on the go.https://kidshealth.org/en/parents/firstaid-kit.html
- Hand Sanitizer: Helps kill germs and prevent the spread of infectious diseases when soap and water are not available.
https://www.fda.gov/drugs/information-drug-class/qa-consumers-hand-sanitizers-and-covid-19
By incorporating these products into your daily routine, you can support your overall health and well-being and take proactive steps towards living a healthier life. Remember to consult with healthcare professionals before starting any new supplements or wellness practices, especially if you have underlying health conditions or concerns.
In summary, while both NeoLife and Norland share a commitment to promoting health and wellness, they differ in their product offerings, ingredient sourcing practices, scientific research approaches, regulatory compliance measures, company philosophies, and customer engagement strategies. Ultimately, the choice between NeoLife and Norland may depend on individual preferences, health goals, and values.https://Norland.com
Title: Assessing the Safety of NeoLife Products
NeoLife, a renowned health and wellness company, offers a range of products claiming various health benefits. However, ensuring the safety of these products is paramount for consumers. Here's an analysis of NeoLife products' safety:
1. **Ingredients Transparency**: NeoLife prides itself on using natural ingredients sourced from reputable suppliers. Transparency in ingredient sourcing is crucial for ensuring safety and efficacy. Consumers can access detailed information about the ingredients used in each product, allowing them to make informed decisions.
2. **Quality Assurance**: NeoLife adheres to rigorous quality control standards throughout the manufacturing process. From raw material sourcing to final product packaging, every step undergoes meticulous scrutiny. Quality assurance measures include testing for purity, potency, and safety to ensure that products meet regulatory requirements and industry standards.
3. **Scientific Research**: NeoLife invests in scientific research to validate the safety and efficacy of its products. Through clinical studies and collaborations with research institutions, the company aims to provide evidence-based support for product claims. This commitment to research contributes to consumer confidence in the safety and effectiveness of NeoLife products.
4. **Regulatory Compliance**: NeoLife operates in compliance with regulatory guidelines and standards set by governing bodies such as the Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA). Adhering to these regulations ensures that products meet safety requirements and undergo thorough testing before reaching the market.
5. **Independent Testing**: In addition to internal quality control measures, NeoLife products may undergo third-party testing for an extra layer of assurance. Independent testing by reputable laboratories helps verify product safety and provides objective assessments of quality and efficacy.
6. **Adverse Event Monitoring**: NeoLife maintains a system for monitoring and reporting adverse events associated with its products. This proactive approach allows the company to promptly address any safety concerns and take appropriate action, such as reformulating products or issuing recalls if necessary.
7. **Customer Feedback**: Customer feedback and testimonials can offer insights into product safety and efficacy. Positive experiences from satisfied customers can enhance trust in NeoLife products, while any reported issues are carefully investigated and addressed by the company.
8. **Consultation with Healthcare Professionals**: NeoLife encourages consumers to consult with healthcare professionals before using its products, especially if they have pre-existing medical conditions or are taking medication. This proactive approach to health management ensures that individuals receive personalized recommendations and can make informed decisions about product safety.
In conclusion, NeoLife products prioritize safety through transparent ingredient sourcing, rigorous quality assurance, scientific research, regulatory compliance, independent testing, adverse event monitoring, customer feedback mechanisms, and consultation with healthcare professionals. While no product can guarantee zero risk, NeoLife strives to provide consumers with safe and effective solutions for their health and wellness needs. By upholding these standards, NeoLife reinforces its commitment to product safety and consumer trust.
10. **Adaptability**: Be willing to adapt to changes in the market, customer preferences, and business strategies to stay competitive and relevant.
Is Neolife A Pyramid Scheme
Ultimate Neolife is not considered a pyramid scheme
Neolife, also known as GNLD (Golden NeoLife Diamite International), has faced criticism and accusations of being a pyramid scheme in the past. However, it's essential to differentiate between legitimate network marketing companies and illegal pyramid schemes.
Here are some points to consider:
1. **Product Focus**: Neolife emphasizes the sale of health and wellness products. A legitimate network marketing company focuses on selling products or services, not solely recruiting members.
2. **Compensation Structure**: While Neolife operates on a multi-level marketing (MLM) model where distributors earn commissions not only from their sales but also from the sales of their downline, it's important to assess whether the primary focus is on product sales or recruitment. Pyramid schemes typically prioritize recruitment over product sales.
3. **Compliance with Laws**: Neolife operates in various countries and must comply with the laws and regulations governing direct selling and MLM businesses in those regions. Investigate whether the company has faced legal challenges or regulatory scrutiny related to its business practices.
4. **Transparency**: Legitimate MLM companies are transparent about their compensation plans, product quality, and business practices. Evaluate whether Neolife provides clear information about its operations and addresses concerns openly.
5. **Customer Base**: A legitimate MLM company should have a significant customer base that purchases and uses its products regularly, not just distributors buying products to qualify for commissions.
6. **Independent Business Owners**: Neolife distributors are considered independent business owners who can earn income through product sales and building their teams. Assess whether the company provides adequate support and training for distributors to succeed in their business endeavors.
Ultimately, whether Neolife or any MLM company not considered a pyramid scheme depends on various factors, including its business practices, focus on product sales versus recruitment, compliance with laws, and transparency. It's essential for individuals to conduct thorough research and exercise caution before getting involved in any MLM opportunity.
The Essential Role of Vitamins in Maintaining Health and Well-being
Introduction:
Vitamins are organic compounds essential for the proper functioning of the human body. While needed in small amounts, they play crucial roles in various physiological processes, from energy production to immune function. In this article, we delve into the significance of vitamins, their sources, and the potential consequences of deficiencies.
Understanding Vitamins:
Vitamins are classified into two categories: fat-soluble (A, D, E, K) and water-soluble (B-complex and C). Fat-soluble vitamins are stored in the body's fatty tissues, while water-soluble vitamins are not stored and are excreted through urine. Each vitamin serves specific functions, such as supporting vision (vitamin A), bone health (vitamin D), antioxidant protection (vitamin E), blood clotting (vitamin K), and energy metabolism (B-complex vitamins).
Sources of Vitamins:
A balanced diet rich in fruits, vegetables, whole grains, lean proteins, and dairy products typically provides an adequate supply of vitamins. For instance, vitamin C is abundant in citrus fruits, strawberries, and bell peppers, while vitamin A is found in carrots, sweet potatoes, and spinach. Fatty fish like salmon and mackerel are excellent sources of vitamin D, while nuts and seeds contain vitamin E. Additionally, fortified foods and dietary supplements can help meet specific vitamin needs, especially in cases of dietary restrictions or insufficient intake.
Consequences of Vitamin Deficiencies:
Insufficient intake or absorption of vitamins can lead to various health issues. For example, vitamin D deficiency may result in weakened bones (osteoporosis) and increased susceptibility to infections, while inadequate vitamin C intake can lead to scurvy, characterized by fatigue, swollen gums, and easy bruising. Vitamin B12 deficiency may cause anemia and neurological problems, while a lack of vitamin
A can impair vision and immune function. It's essential to recognize the symptoms of vitamin deficiencies and address them through dietary changes or supplementation.
Balancing Vitamin Intake:
While vitamins are crucial for health, excessive intake can also have adverse effects. For instance, excessive vitamin A consumption can lead to toxicity, resulting in liver damage and bone abnormalities. Similarly, megadoses of vitamin C can cause gastrointestinal discomfort. Therefore, it's important to follow recommended dietary guidelines and avoid unnecessary supplementation unless advised by a healthcare professional.
Conclusion:
Vitamins are indispensable for maintaining optimal health and well-being. A balanced diet rich in a variety of foods is the best way to ensure an adequate intake of vitamins. By understanding the roles of different vitamins and their food sources, individuals can make informed dietary choices to support their overall health and vitality.
: The Essential Role of Vitamins in Maintaining Health and Well-being
Introduction:
Vitamins are organic compounds essential for the proper functioning of the human body. While needed in small amounts, they play crucial roles in various physiological processes, from energy production to immune function. In this article, we delve into the significance of vitamins, their sources, and the potential consequences of deficiencies.
Understanding Vitamins:
Vitamins are classified into two categories: fat-soluble (A, D, E, K) and water-soluble (B-complex and C). Fat-soluble vitamins are stored in the body's fatty tissues, while water-soluble vitamins are not stored and are excreted through urine. Each vitamin serves specific functions, such as supporting vision (vitamin A), bone health (vitamin D), antioxidant protection (vitamin E), blood clotting (vitamin K), and energy metabolism (B-complex vitamins).
Sources of Vitamins:
A balanced diet rich in fruits, vegetables, whole grains, lean proteins, and dairy products typically provides an adequate supply of vitamins. For instance, vitamin C is abundant in citrus fruits, strawberries, and bell peppers, while vitamin A is found in carrots, sweet potatoes, and spinach. Fatty fish like salmon and mackerel are excellent sources of vitamin D, while nuts and seeds contain vitamin E. Additionally, fortified foods and dietary supplements can help meet specific vitamin needs, especially in cases of dietary restrictions or insufficient intake.
Consequences of Vitamin Deficiencies:
Insufficient intake or absorption of vitamins can lead to various health issues. For example, vitamin D deficiency may result in weakened bones (osteoporosis) and increased susceptibility to infections, while inadequate vitamin C intake can lead to scurvy, characterized by fatigue, swollen gums, and easy bruising. Vitamin B12 deficiency may cause anemia and neurological problems, while a lack of vitamin A can impair vision and immune function. It's essential to recognize the symptoms of vitamin deficiencies and address them through dietary changes or supplementation.
Balancing Vitamin Intake:
While vitamins are crucial for health, excessive intake can also have adverse effects. For instance, excessive vitamin A consumption can lead to toxicity, resulting in liver damage and bone abnormalities. Similarly, megadoses of vitamin C can cause gastrointestinal discomfort. Therefore, it's important to follow recommended dietary guidelines and avoid unnecessary supplementation unless advised by a healthcare professional.
:
Vitamins are indispensable for maintaining optimal health and well-being. A balanced diet rich in a variety of foods is the best way to ensure an adequate intake of vitamins. By understanding the roles of different vitamins and their food sources, individuals can make informed dietary choices to support their overall health and vitality.
NeoLife: A Holistic Approach to Health and Wellness
Introduction:
In an era where health and wellness are paramount, the pursuit of holistic solutions has gained significant traction. Among the array of wellness brands, NeoLife stands out for its commitment to delivering high-quality nutritional products backed by science. In this article, we delve into the ethos of NeoLife, its products, and its impact on promoting a healthier lifestyle.
The NeoLife Philosophy:
At the core of NeoLife's philosophy lies the belief that good nutrition is the foundation of a vibrant and fulfilling life. Founded in 1958 by Jerry Brassfield, NeoLife emphasizes the power of nature and science in creating products that optimize health and vitality. The company's mission is to make the world a healthier and happier place by providing individuals with the tools they need to thrive.
Science-Backed Products:
NeoLife's product line encompasses a diverse range of nutritional supplements, weight management solutions, skincare products, and home care essentials. What sets NeoLife apart is its unwavering commitment to scientific research and quality assurance. The company collaborates with leading scientists, researchers, and health professionals to develop formulations that are safe, effective, and backed by rigorous scientific evidence.
Key Products and Their Benefits:
NeoLifeShake: A nutritious meal replacement shake packed with protein, fiber, vitamins, and minerals to support weight management and muscle health.
Pro Vitality+: A comprehensive daily supplement pack containing essential vitamins, minerals, omega-3 fatty acids, and antioxidants to promote overall wellness.
Nutriance Organic Skincare: A line of organic skincare products formulated with botanical extracts and cutting-edge technology to nourish and rejuvenate the skin.
Golden Home Care: Eco-friendly household cleaning products that are gentle on the environment yet powerful in eliminating dirt and grime.
Community and Support:
Beyond its product offerings, NeoLife fosters a sense of community and support through its network of independent distributors known as NeoLife Club Members. These individuals are passionate advocates for health and wellness, providing personalized guidance and support to customers on their wellness journey. Through educational events, workshops, and online resources, NeoLife empowers individuals to take charge of their health and make informed lifestyle choices.
Conclusion:
In a world inundated with health fads and quick-fix solutions, NeoLifee stands as a beacon of integrity and efficacy in the wellness industry. By prioritizing science, quality, and community, NeoLife continues to make strides in promoting holistic health and empowering individuals to live their best lives. Whether you're seeking to improve your nutrition, enhance your skincare routine, or create a healthier home environment, NeoLife offers a holistic approach to achieving your wellness goals.
NeoLife offers a comprehensive range of vitamin B supplements designed to support various aspects of health and well-being. Here's an overview of some of their key vitamin B products:
1. **NeoLife B-Complex**: This supplement provides a balanced blend of all eight essential B-vitamins, including B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cyanocobalamin). B-vitamins are crucial for energy metabolism, nervous system function, and overall vitality. NeoLife B-Complex ensures optimal absorption and utilization of these important nutrients.
2. **NeoLife B12-Plus**: Specifically formulated to deliver a potent dose of vitamin B12, NeoLife B12-Plus supports red blood cell production, nerve function, and energy metabolism. Vitamin B12 deficiency is common, especially among vegetarians, older adults, and individuals with certain medical conditions. NeoLife B12-Plus provides a convenient solution to ensure adequate B12 intake for optimal health.
3. **NeoLife Stress Relief**: This supplement combines a unique blend of B-vitamins, along with vitamin C and botanical extracts, to support the body's response to stress. Chronic stress can deplete B-vitamin levels and impair adrenal function, leading to fatigue, mood swings, and compromised immune function. NeoLife Stress Relief helps replenish vital nutrients and promotes a sense of calm and well-being.
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Hypertension, also known as high blood pressure, is a long-term medical condition in which the blood pressure in the arteries is persistently elevated.[11] High blood pressure usually does not cause symptoms itself.[1] It is, however, a major risk factor for stroke, coronary artery disease, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia.[2][3][4][12] Hypertension is a major cause of premature death worldwide.[13]
High blood pressure is classified as primary (essential) hypertension or secondary hypertension.[5] About 90–95% of cases are primary, defined as high blood pressure due to nonspecific lifestyle and genetic factors.[5] Lifestyle factors that increase the risk include excess salt in the diet, excess body weight, smoking, physical inactivity and alcohol use.[1][5] The remaining 5–10% of cases are categorized as secondary hypertension, defined as high blood pressure due to a clearly identifiable cause, such as chronic kidney disease, narrowing of the kidney arteries, an endocrine disorder, or the use of birth control pills.[5]
Blood pressure is classified by two measurements, the systolic (first number) and diastolic (second number) pressures.[1] For most adults, normal blood pressure at rest is within the range of 100–140 millimeters mercury (mmHg) systolic and 60–90 mmHg diastolic.[6][7] For most adults, high blood pressure is present if the resting blood pressure is persistently at or above 130/80 or 140/90 mmHg.[5][6][7] Different numbers apply to children.[14] Ambulatory blood pressure monitoring over a 24-hour period appears more accurate than office-based blood pressure measurement.[5][11]
Lifestyle changes and medications can lower blood pressure and decrease the risk of health complications.[8] Lifestyle changes include weight loss, physical exercise, decreased salt intake, reducing alcohol intake, and a healthy diet.[5] If lifestyle changes are not sufficient, blood pressure medications are used.[8] Up to three medications taken concurrently can control blood pressure in 90% of people.[5] The treatment of moderately high arterial blood pressure (defined as >160/100 mmHg) with medications is associated with an improved life expectancy.[15] The effect of treatment of blood pressure between 130/80 mmHg and 160/100 mmHg is less clear, with some reviews finding benefit[6][16][17] and others finding unclear benefit.[18][19][20] High blood pressure affects 33% of the population globally.[9] About half of all people with high blood pressure do not know that they have it.[9] In 2019, high blood pressure was believed to have been a factor in 19% of all deaths (10.4 million globally).[9]
Duration: 3 minutes and 39 seconds.3:39Subtitles available.CC
Video summary (script)
Signs and symptoms
Hypertension is rarely accompanied by symptoms.[1] Half of all people with hypertension are unaware that they have it.[9] Hypertension is usually identified as part of health screening or when seeking healthcare for an unrelated problem.
Some people with high blood pressure report headaches, as well as lightheadedness, vertigo, tinnitus (buzzing or hissing in the ears), altered vision or fainting episodes.[21] These symptoms, however, might be related to associated anxiety rather than the high blood pressure itself.[22]
Long-standing untreated hypertension can cause organ damage with signs such as changes in the optic fundus seen by ophthalmoscopy.[23] The severity of hypertensive retinopathy correlates roughly with the duration or the severity of the hypertension.[21] Other hypertension-caused organ damage include chronic kidney disease and thickening of the heart muscle.[9]
Secondary hypertension
Main article: Secondary hypertension
Secondary hypertension is hypertension due to an identifiable cause, and may result in certain specific additional signs and symptoms. For example, as well as causing high blood pressure, Cushing's syndrome frequently causes truncal obesity,[24] glucose intolerance, moon face, a hump of fat behind the neck and shoulders (referred to as a buffalo hump), and purple abdominal stretch marks.[25] Hyperthyroidism frequently causes weight loss with increased appetite, fast heart rate, bulging eyes, and tremor. Renal artery stenosis may be associated with a localized abdominal bruit to the left or right of the midline, or in both locations. Coarctation of the aorta frequently causes a decreased blood pressure in the lower extremities relative to the arms, or delayed or absent femoral arterial pulses. Pheochromocytoma may cause abrupt episodes of hypertension accompanied by headache, palpitations, pale appearance, and excessive sweating.[25]
Hypertensive crisis
Main article: Hypertensive crisis
Severely elevated blood pressure (equal to or greater than a systolic 180 mmHg or diastolic of 120 mmHg) is referred to as a hypertensive crisis.[26] Hypertensive crisis is categorized as either hypertensive urgency or hypertensive emergency, according to the absence or presence of end organ damage, respectively.[27][28]
In hypertensive urgency, there is no evidence of end organ damage resulting from the elevated blood pressure. In these cases, oral medications are used to lower the BP gradually over 24 to 48 hours.[29]
In hypertensive emergency, there is evidence of direct damage to one or more organs.[30][31] The most affected organs include the brain, kidney, heart and lungs, producing symptoms which may include confusion, drowsiness, chest pain and breathlessness.[29] In hypertensive emergency, the blood pressure must be reduced more rapidly to stop ongoing organ damage;[29] however, there is a lack of randomized controlled trial evidence for this approach.[31]
Pregnancy
Main articles: Gestational hypertension and Pre-eclampsia
Hypertension occurs in approximately 8–10% of pregnancies.[25] Two blood pressure measurements six hours apart of greater than 140/90 mmHg are diagnostic of hypertension in pregnancy.[32] High blood pressure in pregnancy can be classified as pre-existing hypertension, gestational hypertension, or pre-eclampsia.[33] Women who have chronic hypertension before their pregnancy are at increased risk of complications such as premature birth, low birthweight or stillbirth.[34] Women who have high blood pressure and had complications in their pregnancy have three times the risk of developing cardiovascular disease compared to women with normal blood pressure who had no complications in pregnancy.[35][36]
Pre-eclampsia is a serious condition of the second half of pregnancy and following delivery characterised by increased blood pressure and the presence of protein in the urine.[25] It occurs in about 5% of pregnancies and is responsible for approximately 16% of all maternal deaths globally.[25] Pre-eclampsia also doubles the risk of death of the baby around the time of birth.[25] Usually there are no symptoms in pre-eclampsia and it is detected by routine screening. When symptoms of pre-eclampsia occur the most common are headache, visual disturbance (often "flashing lights"), vomiting, pain over the stomach, and swelling. Pre-eclampsia can occasionally progress to a life-threatening condition called eclampsia, which is a hypertensive emergency and has several serious complications including vision loss, brain swelling, seizures, kidney failure, pulmonary edema, and disseminated intravascular coagulation (a blood clotting disorder).[25][37]
In contrast, gestational hypertension is defined as new-onset hypertension during pregnancy without protein in the urine.[33]
Children
Failure to thrive, seizures, irritability, lack of energy, and difficulty in breathing[38] can be associated with hypertension in newborns and young infants. In older infants and children, hypertension can cause headache, unexplained irritability, fatigue, failure to thrive, blurred vision, nosebleeds, and facial paralysis.[38][39]
Causes
Primary hypertension
Main article: Essential hypertension
Hypertension results from a complex interaction of genes and environmental factors. Numerous common genetic variants with small effects on blood pressure have been identified[40] as well as some rare genetic variants with large effects on blood pressure.[41] Also, genome-wide association studies (GWAS) have identified 35 genetic loci related to blood pressure; 12 of these genetic loci influencing blood pressure were newly found.[42] Sentinel SNP for each new genetic locus identified has shown an association with DNA methylation at multiple nearby CpG sites. These sentinel SNP are located within genes related to vascular smooth muscle and renal function. DNA methylation might affect in some way linking common genetic variation to multiple phenotypes even though mechanisms underlying these associations are not understood. Single variant test performed in this study for the 35 sentinel SNP (known and new) showed that genetic variants singly or in aggregate contribute to risk of clinical phenotypes related to high blood pressure.[42]
Blood pressure rises with aging when associated with a western diet and lifestyle and the risk of becoming hypertensive in later life is significant.[43][44] Several environmental factors influence blood pressure. High salt intake raises the blood pressure in salt sensitive individuals; lack of exercise and central obesity can play a role in individual cases. The possible roles of other factors such as caffeine consumption,[45] and vitamin D deficiency[46] are less clear. Insulin resistance, which is common in obesity and is a component of syndrome X (or the metabolic syndrome), also contributes to hypertension.[47]
Events in early life, such as low birth weight, maternal smoking, and lack of breastfeeding may be risk factors for adult essential hypertension, although the mechanisms linking these exposures to adult hypertension remain unclear.[48] An increased rate of high blood uric acid has been found in untreated people with hypertension in comparison with people with normal blood pressure, although it is uncertain whether the former plays a causal role or is subsidiary to poor kidney function.[49] Average blood pressure may be higher in the winter than in the summer.[50] Periodontal disease is also associated with high blood pressure.[51]
Secondary hypertension
Main article: Secondary hypertension
Secondary hypertension results from an identifiable cause. Kidney disease is the most common secondary cause of hypertension.[25] Hypertension can also be caused by endocrine conditions, such as Cushing's syndrome, hyperthyroidism, hypothyroidism, acromegaly, Conn's syndrome or hyperaldosteronism, renal artery stenosis (from atherosclerosis or fibromuscular dysplasia), hyperparathyroidism, and pheochromocytoma.[25][52] Other causes of secondary hypertension include obesity, sleep apnea, pregnancy, coarctation of the aorta, excessive eating of liquorice, excessive drinking of alcohol, certain prescription medicines, herbal remedies, and stimulants such as coffee, cocaine and methamphetamine.[25][53] Arsenic exposure through drinking water has been shown to correlate with elevated blood pressure.[54][55] Depression was also linked to hypertension.[56] Loneliness is also a risk factor.[57] Air pollution may be associated with hypertension.[58]
A 2018 review found that any alcohol increased blood pressure in males while over one or two drinks increased the risk in females.[59]
Pathophysiology
Main article: Pathophysiology of hypertension
Determinants of mean arterial pressure
Illustration depicting the effects of high blood pressure
In most people with established essential hypertension, increased resistance to blood flow (total peripheral resistance) accounts for the high pressure while cardiac output remains normal.[60] There is evidence that some younger people with prehypertension or 'borderline hypertension' have high cardiac output, an elevated heart rate and normal peripheral resistance, termed hyperkinetic borderline hypertension.[61] These individuals develop the typical features of established essential hypertension in later life as their cardiac output falls and peripheral resistance rises with age.[61] Whether this pattern is typical of all people who ultimately develop hypertension is disputed.[62] The increased peripheral resistance in established hypertension is mainly attributable to structural narrowing of small arteries and arterioles,[63] although a reduction in the number or density of capillaries may also contribute.[64]
It is not clear whether or not vasoconstriction of arteriolar blood vessels plays a role in hypertension.[65] Hypertension is also associated with decreased peripheral venous compliance,[66] which may increase venous return, increase cardiac preload and, ultimately, cause diastolic dysfunction. For patients having hypertension, higher heart rate variability (HRV) is a risk factor for atrial fibrillation.[67]
Pulse pressure (the difference between systolic and diastolic blood pressure) is frequently increased in older people with hypertension.[68] This can mean that systolic pressure is abnormally high, but diastolic pressure may be normal or low, a condition termed isolated systolic hypertension.[69] The high pulse pressure in elderly people with hypertension or isolated systolic hypertension is explained by increased arterial stiffness, which typically accompanies aging and may be exacerbated by high blood pressure.[70]
Many mechanisms have been proposed to account for the rise in peripheral resistance in hypertension. Most evidence implicates either disturbances in the kidneys' salt and water handling (particularly abnormalities in the intrarenal renin–angiotensin system)[71] or abnormalities of the sympathetic nervous system.[72] These mechanisms are not mutually exclusive and it is likely that both contribute to some extent in most cases of essential hypertension. It has also been suggested that endothelial dysfunction and vascular inflammation may also contribute to increased peripheral resistance and vascular damage in hypertension.[73][74] Interleukin 17 has garnered interest for its role in increasing the production of several other immune system chemical signals thought to be involved in hypertension such as tumor necrosis factor alpha, interleukin 1, interleukin 6, and interleukin 8.[75]
Excessive sodium or insufficient potassium in the diet leads to excessive intracellular sodium, which contracts vascular smooth muscle, restricting blood flow and so increases blood pressure.[76][77] Non-modulating essential hypertension is a form of salt-sensitive hypertension, where sodium intake does not modulate either adrenal or renal vascular responses to angiotensin II.[78] They make up 25% of the hypertensive population.[79]
Diagnosis
Hypertension is diagnosed on the basis of a persistently high resting blood pressure. Elevated blood pressure measurements on at least two separate occasions is required for a diagnosis of hypertension.[6][7][13]
Measurement technique
For an accurate diagnosis of hypertension to be made, it is essential for proper blood pressure measurement technique to be used.[80] Improper measurement of blood pressure is common and can change the blood pressure reading by up to 10 mmHg, which can lead to misdiagnosis and misclassification of hypertension.[80] Correct blood pressure measurement technique involves several steps. Proper blood pressure measurement requires the person whose blood pressure is being measured to sit quietly for at least five minutes which is then followed by application of a properly fitted blood pressure cuff to a bare upper arm.[80] The person should be seated with their back supported, feet flat on the floor, and with their legs uncrossed.[80] The person whose blood pressure is being measured should avoid talking or moving during this process.[80] The arm being measured should be supported on a flat surface at the level of the heart.[80] Blood pressure measurement should be done in a quiet room so the medical professional checking the blood pressure can hear the Korotkoff sounds while listening to the brachial artery with a stethoscope for accurate blood pressure measurements.[80][81] The blood pressure cuff should be deflated slowly (2–3 mmHg per second) while listening for the Korotkoff sounds.[81] The bladder should be emptied before a person's blood pressure is measured since this can increase blood pressure by up to 15/10 mmHg.[80] Multiple blood pressure readings (at least two) spaced 1–2 minutes apart should be obtained to ensure accuracy.[81] Ambulatory blood pressure monitoring over 12 to 24 hours is the most accurate method to confirm the diagnosis.[82] An exception to this is those with very high blood pressure readings especially when there is poor organ function.[83]
With the availability of 24-hour ambulatory blood pressure monitors and home blood pressure machines, the importance of not wrongly diagnosing those who have white coat hypertension has led to a change in protocols. In the United Kingdom, current best practice is to follow up a single raised clinic reading with ambulatory measurement, or less ideally with home blood pressure monitoring over the course of 7 days.[83] The United States Preventive Services Task Force also recommends getting measurements outside of the healthcare environment.[82] Pseudohypertension in the elderly or noncompressibility artery syndrome may also require consideration. This condition is believed to be due to calcification of the arteries resulting in abnormally high blood pressure readings with a blood pressure cuff while intra arterial measurements of blood pressure are normal.[84] Orthostatic hypertension is when blood pressure increases upon standing.[85]
Other investigations
Once the diagnosis of hypertension has been made, further testing may be performed to find secondary hypertension, identify comorbidities such as diabetes, identify hypertension-caused organ damage such as chronic kidney disease or thickening of the heart muscle, and for cardiovascular disease risk stratification.[9]
Secondary hypertension is more common in preadolescent children, with most cases caused by kidney disease. Primary or essential hypertension is more common in adolescents and adults and has multiple risk factors, including obesity and a family history of hypertension.[86]
Initial assessment upon diagnosis of hypertension should include a complete history and physical examination. The World Health Organization suggests the following initial tests: serum electrolytes, serum creatinine, lipid panel, HbA1c or fasting glucose, urine dipstick and electrocardiogram (ECG/EKG).[9] Serum creatinine is measured to assess for the presence of kidney disease, which can be either the cause or the result of hypertension.[30] eGFR can also provide a baseline measurement of kidney function that can be used to monitor for side effects of certain anti-hypertensive drugs on kidney function. Testing of urine samples for protein is used as a secondary indicator of kidney disease. Lipid panel and glucose tests are done to identify comorbidities such as diabetes and hyperlipidemia and for cardiovascular risk stratification. Electrocardiogram (EKG/ECG) testing is done to check for evidence that the heart is under strain from high blood pressure, such as thickening of the heart muscle or whether the heart has experienced a prior minor disturbance such as a silent heart attack.
Classification in adults
Blood pressure classifications
Categories Systolic blood pressure, mmHg and/or Diastolic blood pressure, mmHg
Method Office 24h ambulatory Office 24h ambulatory
Hypotension[87] <110 <100 or <70 <60
American College of Cardiology/American Heart Association (2017)[88]
Normal <120 <115 and <80 <75
Elevated 120–129 115–124 and <80 <75
Hypertension, stage 1 130–139 125–129 or 80–89 75–79
Hypertension, stage 2 ≥140 ≥130 or ≥90 ≥80
European Society of Hypertension (2023)[7]
Optimal <120 — and <80 —
Normal 120–129 — and/or 80–84 —
High normal 130–139 — and/or 85–89 —
Hypertension, grade 1 140–159 ≥130 and/or 90–99 ≥80
Hypertension, grade 2 160–179 — and/or 100–109 —
Hypertension, grade 3 ≥180 — and/or ≥110 —
Diastolic vs systolic blood pressure chart comparing European Society of Cardiology and European Society of Hypertension classification with reference ranges in children
In people aged 18 years or older, hypertension is defined as either a systolic or a diastolic blood pressure measurement consistently higher than an accepted normal value (this is above 129 or 139 mmHg systolic, 89 mmHg diastolic depending on the guideline).[5][6] Lower thresholds are used if measurements are derived from 24-hour ambulatory or home monitoring.[88]
Children
Hypertension occurs in around 0.2 to 3% of newborns; however, blood pressure is not measured routinely in healthy newborns.[39] Hypertension is more common in high risk newborns. A variety of factors, such as gestational age, postconceptional age and birth weight needs to be taken into account when deciding if a blood pressure is normal in a newborn.[39]
Hypertension defined as elevated blood pressure over several visits affects 1% to 5% of children and adolescents and is associated with long-term risks of ill-health.[89] Blood pressure rises with age in childhood and, in children, hypertension is defined as an average systolic or diastolic blood pressure on three or more occasions equal or higher than the 95th percentile appropriate for the sex, age and height of the child. High blood pressure must be confirmed on repeated visits however before characterizing a child as having hypertension.[89] In adolescents, it has been proposed that hypertension is diagnosed and classified using the same criteria as in adults.[89]
Prevention
Much of the disease burden of high blood pressure is experienced by people who are not labeled as hypertensive.[90] Consequently, population strategies are required to reduce the consequences of high blood pressure and reduce the need for antihypertensive medications. Lifestyle changes are recommended to lower blood pressure.
Recommended lifestyle changes for the prevention of hypertension include:
maintain normal body weight for adults (e.g. body mass index below 25 kg/m2)[7]
reduce dietary sodium intake to <100 mmol/day (<6 g of salt (sodium chloride) or <2.4 g of sodium per day)[7]
engage in regular aerobic physical activity with moderate intensity (minimum 150 minutes per week)[7]
limit alcohol consumption,[7] max 1 drink for women and 2 for men per day[13]
consume a diet rich in whole grains, fruit and vegetables,[7] such as the DASH diet[7]
not smoking[7]
stress reduction and management,[7] e.g. by meditation and yoga[7]
Effective lifestyle modification may lower blood pressure as much as an individual antihypertensive medication. Combinations of two or more lifestyle modifications can achieve even better results.[90] There is considerable evidence that reducing dietary salt intake lowers blood pressure, but whether this translates into a reduction in mortality and cardiovascular disease remains uncertain.[91] Estimated sodium intake ≥6 g/day and <3 g/day are both associated with high risk of death or major cardiovascular disease, but the association between high sodium intake and adverse outcomes is only observed in people with hypertension.[92] Consequently, in the absence of results from randomized controlled trials, the wisdom of reducing levels of dietary salt intake below 3 g/day has been questioned.[91] ESC guidelines mention periodontitis is associated with poor cardiovascular health status.[93]
The value of routine screening for hypertension is debated.[94][95][96] In 2004, the National High Blood Pressure Education Program recommended that children aged 3 years and older have blood pressure measurement at least once at every health care visit[89] and the National Heart, Lung, and Blood Institute and American Academy of Pediatrics made a similar recommendation.[97] However, the American Academy of Family Physicians[98] supports the view of the U.S. Preventive Services Task Force that the available evidence is insufficient to determine the balance of benefits and harms of screening for hypertension in children and adolescents who do not have symptoms.[99][100] The US Preventive Services Task Force recommends screening adults 18 years or older for hypertension with office blood pressure measurement.[96][101]
Management
Main article: Management of hypertension
According to one review published in 2003, reduction of the blood pressure by 5 mmHg can decrease the risk of stroke by 34%, of ischemic heart disease by 21%, and reduce the likelihood of dementia, heart failure, and mortality from cardiovascular disease.[102]
Target blood pressure
See also: Comparison of international blood pressure guidelines
Various expert groups have produced guidelines regarding how low the blood pressure target should be when a person is treated for hypertension. These groups recommend a target below the range 140–160 / 90–100 mmHg for the general population.[7][14][103][104] Cochrane reviews recommend similar targets for subgroups such as people with diabetes[105] and people with prior cardiovascular disease.[106] Additionally, Cochrane reviews have found that for older individuals with moderate to high cardiovascular risk, the benefits of trying to achieve a lower than standard blood pressure target (at or below 140/90 mmHg) are outweighed by the risk associated with the intervention.[107] These findings may not be applicable to other populations.[107]
Many expert groups recommend a slightly higher target of 150/90 mmHg for those over somewhere between 60 and 80 years of age.[103][104][108] The JNC 8 and American College of Physicians recommend the target of 150/90 mmHg for those over 60 years of age,[14][108] but some experts within these groups disagree with this recommendation.[109] Some expert groups have also recommended slightly lower targets in those with diabetes[110] or chronic kidney disease,[111] but others recommend the same target as for the general population.[14][105] The issue of what is the best target and whether targets should differ for high risk individuals is unresolved,[112] although some experts propose more intensive blood pressure lowering than advocated in some guidelines.[113]
For people who have never experienced cardiovascular disease who are at a 10-year risk of cardiovascular disease of less than 10%, the 2017 American Heart Association guidelines recommend medications if the systolic blood pressure is >140 mmHg or if the diastolic BP is >90 mmHg.[6] For people who have experienced cardiovascular disease or those who are at a 10-year risk of cardiovascular disease of greater than 10%, it recommends medications if the systolic blood pressure is >130 mmHg or if the diastolic BP is >80 mmHg.[6]
Lifestyle modifications
The first line of treatment for hypertension is lifestyle changes, including dietary changes, physical activity, and weight loss. Though these have all been recommended in scientific advisories,[114] a Cochrane systematic review found no evidence (due to lack of data) for effects of weight loss diets on death, long-term complications or adverse events in persons with hypertension.[115] The review did find a decrease in body weight and blood pressure.[115] Their potential effectiveness is similar to and at times exceeds a single medication.[7] If hypertension is high enough to justify immediate use of medications, lifestyle changes are still recommended in conjunction with medication.
Dietary changes shown to reduce blood pressure include diets with low sodium,[116][117] the DASH diet (Dietary Approaches to Stop Hypertension),[118] which was the best against 11 other diet in an umbrella review,[119] and plant-based diets.[120] There is some evidence green tea consumption may help lower blood pressure, but this is insufficient for it to be recommended as a treatment.[121] Hibiscus tea consumption may reduce blood pressure.[122][123] Beetroot juice consumption also may lower blood pressure.[124][125][126]
Increasing dietary potassium has a potential benefit for lowering the risk of hypertension.[127][128] The 2015 Dietary Guidelines Advisory Committee (DGAC) stated that potassium is one of the shortfall nutrients which is under-consumed in the United States.[129] However, people who take certain antihypertensive medications (such as ACE-inhibitors or ARBs) should not take potassium supplements or potassium-enriched salts due to the risk of high levels of potassium.[130]
Physical exercise regimens which are shown to reduce blood pressure include isometric resistance exercise, aerobic exercise, resistance exercise, and device-guided breathing.[131]
Stress reduction techniques such as biofeedback or transcendental meditation may be considered as an add-on to other treatments to reduce hypertension, but do not have evidence for preventing cardiovascular disease on their own.[131][132][133] Self-monitoring and appointment reminders might support the use of other strategies to improve blood pressure control, but need further evaluation.[134]
Medications
Several classes of medications, collectively referred to as antihypertensive medications, are available for treating hypertension.
First-line medications for hypertension include thiazide-diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors (ACE inhibitors), and angiotensin receptor blockers (ARBs).[135][14] These medications may be used alone or in combination (ACE inhibitors and ARBs are not recommended for use together); the latter option may serve to minimize counter-regulatory mechanisms that act to restore blood pressure values to pre-treatment levels,[14][136] although the evidence for first-line combination therapy is not strong enough.[137] Most people require more than one medication to control their hypertension.[114] Medications for blood pressure control should be implemented by a stepped care approach when target levels are not reached.[134] Withdrawal of such medications in the elderly can be considered by healthcare professionals, because there is no strong evidence of an effect on mortality, myocardial infarction, or stroke.[138]
Previously, beta-blockers such as atenolol were thought to have similar beneficial effects when used as first-line therapy for hypertension. However, a Cochrane review that included 13 trials found that the effects of beta-blockers are inferior to that of other antihypertensive medications in preventing cardiovascular disease.[139]
The prescription of antihypertensive medication for children with hypertension has limited evidence. There is limited evidence which compare it with placebo and shows modest effect to blood pressure in short term. Administration of higher dose did not make the reduction of blood pressure greater.[140]
Resistant hypertension
Resistant hypertension is defined as high blood pressure that remains above a target level, in spite of being prescribed three or more antihypertensive drugs simultaneously with different mechanisms of action.[141] Failing to take prescribed medications as directed is an important cause of resistant hypertension.[142]
Some common secondary causes of resistant hypertension include obstructive sleep apnea, primary aldosteronism and renal artery stenosis, and some rare secondary causes are pheochromocytoma and coarctation of the aorta.[143] As many as one in five people with resistant hypertension have primary aldosteronism, which is a treatable and sometimes curable condition.[144] Resistant hypertension may also result from chronically high activity of the autonomic nervous system, an effect known as neurogenic hypertension.[145] Electrical therapies that stimulate the baroreflex are being studied as an option for lowering blood pressure in people in this situation.[146]
Refractory hypertension is described by one source as elevated blood pressure unmitigated by five or more concurrent antihypertensive agents of different classes.[147] People with refractory hypertension typically have increased sympathetic nervous system activity, and are at high risk for more severe cardiovascular diseases and all-cause mortality.[147][148]
Epidemiology
Rates of hypertension in adult men in 2014[149]
Disability-adjusted life year for hypertensive heart disease per 100,000 inhabitants in 2004:[150]
no data
<110
110–220
220–330
330–440
440–550
550–660
660–770
770–880
880–990
990–1100
1100–1600
>1600
Adults
As of 2019, one in three or 33% of the world population were estimated to have hypertension.[9][10] Of all people with hypertension, about 46% do not have a diagnosis of hypertension and are unaware that they have the condition.[13][9] In 1975, almost 600 million people had a diagnosis of hypertension, a number which increased to 1.13 billion by 2015 mostly due to risk factors for hypertension increasing in low- and middle-income countries.[13]
Hypertension is slightly more frequent in men.[10] In people aged under 50 years, more men than women have hypertension,[10] and in ages above 50 years the prevalence of hypertension is the same in men and women.[10] In ages above 65 years, more women than men have hypertension.[7] Hypertension becomes more common with age.[5] Hypertension is common in high, medium, and low-income countries.[13][2] It is more common in people of low socioeconomic status.[151] Hypertension is around twice as common in diabetics.[152]
In 2019, rates of diagnosed hypertension were highest in Africa (30% for both sexes), and lowest in the Americas (18% for both sexes).[10] Rates also vary markedly within regions with country-level rates as low as 22.8% (men) and 18.4% (women) in Peru and as high as 61.6% (men) and 50.9% (women) in Paraguay.[10]
In 1995 it was estimated that 24% of the United States population had hypertension or were taking antihypertensive medication.[153] By 2004 this had increased to 29%[154][155] and further to 32% (76 million US adults) by 2017.[6] In 2017, with the American guidelines' change in definition for hypertension, 46% of people in the United States are affected.[6] African-American adults in the United States have among the highest rates of hypertension in the world at 44%.[156] Differences in hypertension rates are multifactorial and under study.[157]
Children
Rates of high blood pressure in children and adolescents have increased in the last 20 years in the United States.[158] Childhood hypertension, particularly in pre-adolescents, is more often secondary to an underlying disorder than in adults. Kidney disease is the most common secondary cause of hypertension in children and adolescents. Nevertheless, primary or essential hypertension accounts for most cases.[159]
Prognosis
Main article: Complications of hypertension
Diagram illustrating the main complications of persistent high blood pressure
Hypertension is the most important preventable risk factor for premature death worldwide.[160] It increases the risk of ischemic heart disease,[161] stroke,[25] peripheral vascular disease,[162] and other cardiovascular diseases, including heart failure, aortic aneurysms, diffuse atherosclerosis, chronic kidney disease, atrial fibrillation, cancers, leukemia and pulmonary embolism.[12][25] Hypertension is also a risk factor for cognitive impairment and dementia.[25] Other complications include hypertensive retinopathy and hypertensive nephropathy.[30]
History
Main article: History of hypertension
Image of veins from Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus
Measurement
Modern understanding of the cardiovascular system began with the work of physician William Harvey (1578–1657), who described the circulation of blood in his book "De motu cordis". The English clergyman Stephen Hales made the first published measurement of blood pressure in 1733.[163][164] However, hypertension as a clinical entity came into its own with the invention of the cuff-based sphygmomanometer by Scipione Riva-Rocci in 1896.[165] This allowed easy measurement of systolic pressure in the clinic. In 1905, Nikolai Korotkoff improved the technique by describing the Korotkoff sounds that are heard when the artery is ausculted with a stethoscope while the sphygmomanometer cuff is deflated.[164] This permitted systolic and diastolic pressure to be measured.
Identification
The symptoms similar to symptoms of patients with hypertensive crisis are discussed in medieval Persian medical texts in the chapter of "fullness disease".[166] The symptoms include headache, heaviness in the head, sluggish movements, general redness and warm to touch feel of the body, prominent, distended and tense vessels, fullness of the pulse, distension of the skin, coloured and dense urine, loss of appetite, weak eyesight, impairment of thinking, yawning, drowsiness, vascular rupture, and hemorrhagic stroke.[167] Fullness disease was presumed to be due to an excessive amount of blood within the blood vessels.
Descriptions of hypertension as a disease came among others from Thomas Young in 1808 and especially Richard Bright in 1836.[163] The first report of elevated blood pressure in a person without evidence of kidney disease was made by Frederick Akbar Mahomed (1849–1884).[168]
Until the 1990s, systolic hypertension was defined as systolic blood pressure of 160 mm Hg or greater.[169] In 1993, the WHO/ISH guidelines defined 140 mmHg as the threshold for hypertension.[170]
Treatment
Historically the treatment for what was called the "hard pulse disease" consisted in reducing the quantity of blood by bloodletting or the application of leeches.[163] This was advocated by The Yellow Emperor of China, Cornelius Celsus, Galen, and Hippocrates.[163] The therapeutic approach for the treatment of hard pulse disease included changes in lifestyle (staying away from anger and sexual intercourse) and dietary program for patients (avoiding the consumption of wine, meat, and pastries, reducing the volume of food in a meal, maintaining a low-energy diet and the dietary usage of spinach and vinegar).
In the 19th and 20th centuries, before effective pharmacological treatment for hypertension became possible, three treatment modalities were used, all with numerous side-effects: strict sodium restriction (for example the rice diet[163]), sympathectomy (surgical ablation of parts of the sympathetic nervous system), and pyrogen therapy (injection of substances that caused a fever, indirectly reducing blood pressure).[163][171]
The first chemical for hypertension, sodium thiocyanate, was used in 1900 but had many side effects and was unpopular.[163] Several other agents were developed after the Second World War, the most popular and reasonably effective of which were tetramethylammonium chloride, hexamethonium, hydralazine, and reserpine (derived from the medicinal plant Rauvolfia serpentina). None of these were well tolerated.[172][173] A major breakthrough was achieved with the discovery of the first well-tolerated orally available agents. The first was chlorothiazide, the first thiazide diuretic and developed from the antibiotic sulfanilamide, which became available in 1958.[163][174] Subsequently, beta blockers, calcium channel blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers, and renin inhibitors were developed as antihypertensive agents.[171]
Society and culture
Awareness
Graph showing prevalence of awareness, treatment and control of hypertension compared between the four studies of NHANES[154]
The World Health Organization has identified hypertension (high blood pressure) as the leading cause of cardiovascular mortality.[175] The World Hypertension League (WHL), an umbrella organization of 85 national hypertension societies and leagues, recognized that more than 50% of the hypertensive population worldwide are unaware of their condition.[175] To address this problem, the WHL initiated a global awareness campaign on hypertension in 2005 and dedicated 17 May of each year as World Hypertension Day.[176]
Economics
High blood pressure is the most common chronic medical problem prompting visits to primary health care providers in US. The American Heart Association estimated the direct and indirect costs of high blood pressure in 2010 as $76.6 billion.[156] In the US 80% of people with hypertension are aware of their condition, 71% take some antihypertensive medication, but only 48% of people aware that they have hypertension adequately control it.[156] Adequate management of hypertension can be hampered by inadequacies in the diagnosis, treatment, or control of high blood pressure.[177] Health care providers face many obstacles to achieving blood pressure control, including resistance to taking multiple medications to reach blood pressure goals. People also face the challenges of adhering to medicine schedules and making lifestyle changes. Nonetheless, the achievement of blood pressure goals is possible, and most importantly, lowering blood pressure significantly reduces the risk of death due to heart disease and stroke, the development of other debilitating conditions, and the cost associated with advanced medical care.[178][179]
Other animals
Hypertension in cats is indicated with a systolic blood pressure greater than 150 mmHg, with amlodipine the usual first-line treatment. A cat with a systolic blood pressure above 170 mmHg is considered hypertensive. If a cat has other problems such as any kidney disease or retina detachment then a blood pressure below 160 mmHg may also need to be monitored.[180]
Normal blood pressure in dogs can differ substantially between breeds but hypertension is often diagnosed if systolic blood pressure is above 160 mmHg particularly if this is associated with target organ damage.[181] Inhibitors of the renin-angiotensin system and calcium channel blockers are often used to treat hypertension in dogs, although other drugs may be indicated for specific conditions causing high blood pressure.[181]
S
Obesity is a medical condition, sometimes considered a disease,[8][9][10] in which excess body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classified as obese when their body mass index (BMI)—a person's weight divided by the square of the person's height—is over 30 kg/m2; the range 25–30 kg/m2 is defined as overweight.[1] Some East Asian countries use lower values to calculate obesity.[11] Obesity is a major cause of disability and is correlated with various diseases and conditions, particularly cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis.[2][12][13]
Obesity has individual, socioeconomic, and environmental causes. Some known causes are diet, physical activity, automation, urbanization, genetic susceptibility, medications, mental disorders, economic policies, endocrine disorders, and exposure to endocrine-disrupting chemicals.[1][4][14][15]
While a majority of obese individuals at any given time attempt to lose weight and are often successful, maintaining weight loss long-term is rare.[16] There is no effective, well-defined, evidence-based intervention for preventing obesity. Obesity prevention requires a complex approach, including interventions at societal, community, family, and individual levels.[1][13] Changes to diet as well as exercising are the main treatments recommended by health professionals.[2] Diet quality can be improved by reducing the consumption of energy-dense foods, such as those high in fat or sugars, and by increasing the intake of dietary fiber, if these dietary choices are available, affordable, and accessible.[1] Medications can be used, along with a suitable diet, to reduce appetite or decrease fat absorption.[5] If diet, exercise, and medication are not effective, a gastric balloon or surgery may be performed to reduce stomach volume or length of the intestines, leading to feeling full earlier, or a reduced ability to absorb nutrients from food.[6][17]
Obesity is a leading preventable cause of death worldwide, with increasing rates in adults and children.[18] In 2022, over 1 billion people were obese worldwide (879 million adults and 159 million children), representing more than a double of adult cases (and four times higher than cases among children) registered in 1990.[7][19] Obesity is more common in women than in men.[1] Today, obesity is stigmatized in most of the world. Conversely, some cultures, past and present, have a favorable view of obesity, seeing it as a symbol of wealth and fertility.[2][20] The World Health Organization, the US, Canada, Japan, Portugal, Germany, the European Parliament and medical societies, e.g. the American Medical Association, classify obesity as a disease. Others, such as the UK, do not.[21][22][23][24]
Classification
Main article: Classification of obesity
Category[25] BMI (kg/m2)
Underweight < 18.5
Normal weight 18.5 – 24.9
Overweight 25.0 – 29.9
Obese (class I) 30.0 – 34.9
Obese (class II) 35.0 – 39.9
Obese (class III) ≥ 40.0
A front and side view of a "super obese" male torso. Stretch marks of the skin are visible along with gynecomastia.
A "super obese" male with a BMI of 53 kg/m2: weight 182 kg (401 lb), height 185 cm (6 ft 1 in). He presents with stretch marks and enlarged breasts.
Obesity is typically defined as a substantial accumulation of body fat that could impact health.[26] Medical organizations tend to classify people as obese based on body mass index (BMI) – a ratio of a person's weight in kilograms to the square of their height in meters. For adults, the World Health Organization (WHO) defines "overweight" as a BMI 25 or higher, and "obese" as a BMI 30 or higher.[26] The U.S. Centers for Disease Control and Prevention (CDC) further subdivides obesity based on BMI, with a BMI 30 to 35 called class 1 obesity; 35 to 40, class 2 obesity; and 40+, class 3 obesity.[27]
For children, obesity measures take age into consideration along with height and weight. For children aged 5–19, the WHO defines obesity as a BMI two standard deviations above the median for their age (a BMI around 18 for a five-year old; around 30 for a 19-year old).[26][28] For children under five, the WHO defines obesity as a weight three standard deviations above the median for their height.[26]
Some modifications to the WHO definitions have been made by particular organizations.[29] The surgical literature breaks down class II and III or only class III obesity into further categories whose exact values are still disputed.[30]
Any BMI ≥ 35 or 40 kg/m2 is severe obesity.
A BMI of ≥ 35 kg/m2 and experiencing obesity-related health conditions or ≥ 40 or 45 kg/m2 is morbid obesity.
A BMI of ≥ 45 or 50 kg/m2 is super obesity.
As Asian populations develop negative health consequences at a lower BMI than Caucasians, some nations have redefined obesity; Japan has defined obesity as any BMI greater than 25 kg/m2[11] while China uses a BMI of greater than 28 kg/m2.[29]
The preferred obesity metric in scholarly circles is the body fat percentage (BF%) – the ratio of the total weight of person's fat to his or her body weight, and BMI is viewed merely as a way to approximate BF%.[31] According to American Society of Bariatric Physicians, levels in excess of 32% for women and 25% for men are generally considered to indicate obesity.[32]
BMI ignores variations between individuals in amounts of lean body mass, particularly muscle mass. Individuals involved in heavy physical labor or sports may have high BMI values despite having little fat. For example, more than half of all NFL players are classified as "obese" (BMI ≥ 30), and 1 in 4 are classified as "extremely obese" (BMI ≥ 35), according to the BMI metric.[33] However, their mean body fat percentage, 14%, is well within what is considered a healthy range.[34] Similarly, Sumo wrestlers may be categorized by BMI as "severely obese" or "very severely obese" but many Sumo wrestlers are not categorized as obese when body fat percentage is used instead (having <25% body fat).[35] Some Sumo wrestlers were found to have no more body fat than a non-Sumo comparison group, with high BMI values resulting from their high amounts of lean body mass.[35]
Effects on health
Obesity increases a person's risk of developing various metabolic diseases, cardiovascular disease, osteoarthritis, Alzheimer disease, depression, and certain types of cancer.[36] Depending on the degree of obesity and the presence of comorbid disorders, obesity is associated with an estimated 2–20 year shorter life expectancy.[37][36] High BMI is a marker of risk for, but not a direct cause of, diseases caused by diet and physical activity.[13]
Mortality
Obesity is one of the leading preventable causes of death worldwide.[38][39][40] The mortality risk is lowest at a BMI of 20–25 kg/m2[41][37][42] in non-smokers and at 24–27 kg/m2 in current smokers, with risk increasing along with changes in either direction.[43][44] This appears to apply in at least four continents.[42] Other research suggests that the association of BMI and waist circumference with mortality is U- or J-shaped, while the association between waist-to-hip ratio and waist-to-height ratio with mortality is more positive.[45] In Asians the risk of negative health effects begins to increase between 22 and 25 kg/m2.[46] In 2021, the World Health Organization estimated that obesity caused at least 2.8 million deaths annually.[47] On average, obesity reduces life expectancy by six to seven years,[2][48] a BMI of 30–35 kg/m2 reduces life expectancy by two to four years,[37] while severe obesity (BMI ≥ 40 kg/m2) reduces life expectancy by ten years.[37]
Morbidity
Main article: Obesity-associated morbidity
Obesity increases the risk of many physical and mental conditions. These comorbidities are most commonly shown in metabolic syndrome,[2] a combination of medical disorders which includes: diabetes mellitus type 2, high blood pressure, high blood cholesterol, and high triglyceride levels.[49] A study from the RAK Hospital found that obese people are at a greater risk of developing long COVID.[50] The CDC has found that obesity is the single strongest risk factor for severe COVID-19 illness.[51]
Complications are either directly caused by obesity or indirectly related through mechanisms sharing a common cause such as a poor diet or a sedentary lifestyle. The strength of the link between obesity and specific conditions varies. One of the strongest is the link with type 2 diabetes. Excess body fat underlies 64% of cases of diabetes in men and 77% of cases in women.[52]: 9
Health consequences fall into two broad categories: those attributable to the effects of increased fat mass (such as osteoarthritis, obstructive sleep apnea, social stigmatization) and those due to the increased number of fat cells (diabetes, cancer, cardiovascular disease, non-alcoholic fatty liver disease).[2][53] Increases in body fat alter the body's response to insulin, potentially leading to insulin resistance. Increased fat also creates a proinflammatory state,[54][55] and a prothrombotic state.[53][56]
Parts of this article (those related to table below) need to be updated. Please help update this article to reflect recent events or newly available information. (March 2022)
Medical field Condition Medical field Condition
Cardiology
Coronary heart disease:[57] angina and myocardial infarction
Congestive heart failure[2][58]
High blood pressure[2]
Abnormal cholesterol levels[2]
Deep vein thrombosis and pulmonary embolism[59]
Dermatology
Acanthosis nigricans[60]
Lymphedema[60]
Cellulitis[60]
Hirsutism[60]
Intertrigo[61]
Endocrinology and reproductive medicine
Diabetes mellitus[2]
Polycystic ovarian syndrome[2]
Menstrual disorders[2]
Infertility[2][62]
Complications during pregnancy[2][62]
Birth defects[2]
Intrauterine fetal death[62]
Gastroenterology
Gastroesophageal reflux disease[63]
Fatty liver disease[63]
Cholelithiasis (gallstones)[63]
Neurology
Stroke[2]
Meralgia paresthetica[64]
Migraines[65]
Carpal tunnel syndrome[66]
Dementia[67]
Idiopathic intracranial hypertension[68]
Multiple sclerosis[69]
Oncology[70]
Esophageal
Colorectal
Pancreatic
Gallbladder
Endometrial
Kidney
Leukemia
Hepatocellular carcinoma[63]
Malignant melanoma
Psychiatry
Depression in women[2]
Social stigmatization[2]
Respirology
Obstructive sleep apnea[2][71]
Obesity hypoventilation syndrome[2][71]
Asthma[2][71]
Increased complications during general anaesthesia[2]
increased risk of severe COVID-19[72]
Rheumatology and orthopedics
Gout[73]
Poor mobility[74]
Osteoarthritis[2]
Low back pain[75]
Urology and Nephrology
Erectile dysfunction[76]
Urinary incontinence[77]
Chronic renal failure[78]
Hypogonadism[79]
Buried penis[80]
Metrics of health
Main article: Metabolically healthy obesity
Newer research has focused on methods of identifying healthier obese people by clinicians, and not treating obese people as a monolithic group.[81] Obese people who do not experience medical complications from their obesity are sometimes called (metabolically) healthy obese, but the extent to which this group exists (especially among older people) is in dispute.[82] The number of people considered metabolically healthy depends on the definition used, and there is no universally accepted definition.[83] There are numerous obese people who have relatively few metabolic abnormalities, and a minority of obese people have no medical complications.[83] The guidelines of the American Association of Clinical Endocrinologists call for physicians to use risk stratification with obese patients when considering how to assess their risk of developing type 2 diabetes.[84]: 59–60
In 2014, the BioSHaRE–EU Healthy Obese Project (sponsored by Maelstrom Research, a team under the Research Institute of the McGill University Health Centre) came up with two definitions for healthy obesity, one more strict and one less so:[82][85]
BioSHaRE Healthy Obese (HOP) Project Criteria (2014)
A patient must have a body mass index ≥ 30, and all of the following:
Less strict More strict
Blood pressure measured as follows, with no pharmaceutical help
Overall (mmHg) ≤ 140 ≤ 130
Systolic (mmHg) N/A ≤ 85[clarification needed]
Diastolic (mmHg) ≤ 90 N/A
Blood sugar level measured as follows, with no pharmaceutical help
Blood glucose (mmol/L) ≤ 7.0 ≤ 6.1
Triglycerides measured as follows, with no pharmaceutical help
Fasting (mmol/L) ≤ 1.7
Non-fasting (mmol/L) ≤ 2.1
High-density lipoprotein measured as follows, with no pharmaceutical help
Men (mmol/L) > 1.03
Women (mmol/L) > 1.3
No diagnosis of any cardiovascular disease
To come up with these criteria, BioSHaRE controlled for age and tobacco use, researching how both may effect the metabolic syndrome associated with obesity, but not found to exist in the metabolically healthy obese.[86] Other definitions of metabolically healthy obesity exist, including ones based on waist circumference rather than BMI, which is unreliable in certain individuals.[83]
Another identification metric for health in obese people is calf strength, which is positively correlated with physical fitness in obese people.[87] Body composition in general is hypothesized to help explain the existence of metabolically healthy obesity—the metabolically healthy obese are often found to have low amounts of ectopic fat (fat stored in tissues other than adipose tissue) despite having overall fat mass equivalent in weight to obese people with metabolic syndrome.[88]: 1282
Survival paradox
See also: Obesity paradox
Although the negative health consequences of obesity in the general population are well supported by the available research evidence, health outcomes in certain subgroups seem to be improved at an increased BMI, a phenomenon known as the obesity survival paradox.[89] The paradox was first described in 1999 in overweight and obese people undergoing hemodialysis[89] and has subsequently been found in those with heart failure and peripheral artery disease (PAD).[90]
In people with heart failure, those with a BMI between 30.0 and 34.9 had lower mortality than those with a normal weight. This has been attributed to the fact that people often lose weight as they become progressively more ill.[91] Similar findings have been made in other types of heart disease. People with class I obesity and heart disease do not have greater rates of further heart problems than people of normal weight who also have heart disease. In people with greater degrees of obesity, however, the risk of further cardiovascular events is increased.[92][93] Even after cardiac bypass surgery, no increase in mortality is seen in the overweight and obese.[94] One study found that the improved survival could be explained by the more aggressive treatment obese people receive after a cardiac event.[95] Another study found that if one takes into account chronic obstructive pulmonary disease (COPD) in those with PAD, the benefit of obesity no longer exists.[90]
Causes
The "a calorie is a calorie" model of obesity posits a combination of excessive food energy intake and a lack of physical activity as the cause of most cases of obesity.[96] A limited number of cases are due primarily to genetics, medical reasons, or psychiatric illness.[15] In contrast, increasing rates of obesity at a societal level are felt to be due to an easily accessible and palatable diet,[97] increased reliance on cars, and mechanized manufacturing.[98][99]
Some other factors have been proposed as causes towards rising rates of obesity worldwide, including insufficient sleep, endocrine disruptors, increased usage of certain medications (such as atypical antipsychotics),[100] increases in ambient temperature, decreased rates of smoking,[101] demographic changes, increasing maternal age of first-time mothers, changes to epigenetic dysregulation from the environment, increased phenotypic variance via assortative mating, social pressure to diet,[102] among others. According to one study, factors like these may play as big of a role as excessive food energy intake and a lack of physical activity;[103] however, the relative magnitudes of the effects of any proposed cause of obesity is varied and uncertain, as there is a general need for randomized controlled trials on humans before definitive statement can be made.[104]
According to the Endocrine Society, there is "growing evidence suggesting that obesity is a disorder of the energy homeostasis system, rather than simply arising from the passive accumulation of excess weight".[105]
Diet
Main article: Diet and obesity
(Left) A world map with countries colored to reflect the food energy consumption of their people in 1961. North America, Europe, and Australia have relatively high intake, while Africa and Asia consume much less.
1961
(Right) A world map with countries colored to reflect the food energy consumption of their people in 2001–2003. Consumption in North America, Europe, and Australia has increased with respect to previous levels in 1971. Food consumption has also increased substantially in many parts of Asia. However, food consumption in Africa remains low.
2001–03
Map of dietary energy availability per person per day in 1961 (left) and 2001–2003 (right)[106] Calories per person per day (kilojoules per person per day)
No data
<1,600 (<6,700)
1,600–1,800 (6,700–7,500)
1,800–2,000 (7,500–8,400)
2,000–2,200 (8,400–9,200)
2,200–2,400 (9,200–10,000)
2,400–2,600 (10,000–10,900)
2,600–2,800 (10,900–11,700)
2,800–3,000 (11,700–12,600)
3,000–3,200 (12,600–13,400)
3,200–3,400 (13,400–14,200)
3,400–3,600 (14,200–15,100)
>3,600 (>15,100)
A graph showing a gradual increase in global food energy consumption per person per day between 1961 and 2002.
Average per capita energy consumption of the world from 1961 to 2002[106]
Excess appetite for palatable, high-calorie food (especially fat, sugar, and certain animal proteins) is seen as the primary factor driving obesity worldwide, likely because of imbalances in neurotransmitters affecting the drive to eat.[107] Dietary energy supply per capita varies markedly between different regions and countries. It has also changed significantly over time.[106] From the early 1970s to the late 1990s the average food energy available per person per day (the amount of food bought) increased in all parts of the world except Eastern Europe. The United States had the highest availability with 3,654 calories (15,290 kJ) per person in 1996.[106] This increased further in 2003 to 3,754 calories (15,710 kJ).[106] During the late 1990s, Europeans had 3,394 calories (14,200 kJ) per person, in the developing areas of Asia there were 2,648 calories (11,080 kJ) per person, and in sub-Saharan Africa people had 2,176 calories (9,100 kJ) per person.[106][108] Total food energy consumption has been found to be related to obesity.[109]
Prevalence of obesity in the adult population by region (2000 - 2016)
The widespread availability of dietary guidelines[110] has done little to address the problems of overeating and poor dietary choice.[111] From 1971 to 2000, obesity rates in the United States increased from 14.5% to 30.9%.[112] During the same period, an increase occurred in the average amount of food energy consumed. For women, the average increase was 335 calories (1,400 kJ) per day (1,542 calories (6,450 kJ) in 1971 and 1,877 calories (7,850 kJ) in 2004), while for men the average increase was 168 calories (700 kJ) per day (2,450 calories (10,300 kJ) in 1971 and 2,618 calories (10,950 kJ) in 2004). Most of this extra food energy came from an increase in carbohydrate consumption rather than fat consumption.[113] The primary sources of these extra carbohydrates are sweetened beverages, which now account for almost 25 percent of daily food energy in young adults in America,[114] and potato chips.[115] Consumption of sweetened beverages such as soft drinks, fruit drinks, and iced tea is believed to be contributing to the rising rates of obesity[116][117] and to an increased risk of metabolic syndrome and type 2 diabetes.[118] Vitamin D deficiency is related to diseases associated with obesity.[119]
As societies become increasingly reliant on energy-dense, big-portions, and fast-food meals, the association between fast-food consumption and obesity becomes more concerning.[120] In the United States, consumption of fast-food meals tripled and food energy intake from these meals quadrupled between 1977 and 1995.[121]
Agricultural policy and techniques in the United States and Europe have led to lower food prices. In the United States, subsidization of corn, soy, wheat, and rice through the U.S. farm bill has made the main sources of processed food cheap compared to fruits and vegetables.[122] Calorie count laws and nutrition facts labels attempt to steer people toward making healthier food choices, including awareness of how much food energy is being consumed.
Obese people consistently under-report their food consumption as compared to people of normal weight.[123] This is supported both by tests of people carried out in a calorimeter room[124] and by direct observation.
Sedentary lifestyle
See also: Sedentary lifestyle and Exercise trends
A sedentary lifestyle may play a significant role in obesity.[52]: 10 Worldwide there has been a large shift towards less physically demanding work,[125][126][127] and currently at least 30% of the world's population gets insufficient exercise.[126] This is primarily due to increasing use of mechanized transportation and a greater prevalence of labor-saving technology in the home.[125][126][127] In children, there appear to be declines in levels of physical activity (with particularly strong declines in the amount of walking and physical education), likely due to safety concerns, changes in social interaction (such as fewer relationships with neighborhood children), and inadequate urban design (such as too few public spaces for safe physical activity).[128] World trends in active leisure time physical activity are less clear. The World Health Organization indicates people worldwide are taking up less active recreational pursuits, while research from Finland[129] found an increase and research from the United States found leisure-time physical activity has not changed significantly.[130] Physical activity in children may not be a significant contributor.[131]
In both children and adults, there is an association between television viewing time and the risk of obesity.[132][133][134] Increased media exposure increases the rate of childhood obesity, with rates increasing proportionally to time spent watching television.[135]
Genetics
Main article: Genetics of obesity
This section needs to be updated. Please help update this article to reflect recent events or newly available information. (July 2021)
A painting of a dark haired pink cheeked obese nude young female leaning against a table. She is holding grapes and grape leaves in her left hand which cover her genitalia.
"La Monstrua Desnuda" (The Nude Monster), an 1680 painting by Juan Carreno de Miranda of a girl presumed to have Prader–Willi syndrome[136]
Like many other medical conditions, obesity is the result of an interplay between genetic and environmental factors.[137] Polymorphisms in various genes controlling appetite and metabolism predispose to obesity when sufficient food energy is present. As of 2006, more than 41 of these sites on the human genome have been linked to the development of obesity when a favorable environment is present.[138] People with two copies of the FTO gene (fat mass and obesity associated gene) have been found on average to weigh 3–4 kg more and have a 1.67-fold greater risk of obesity compared with those without the risk allele.[139] The differences in BMI between people that are due to genetics varies depending on the population examined from 6% to 85%.[140]
Obesity is a major feature in several syndromes, such as Prader–Willi syndrome, Bardet–Biedl syndrome, Cohen syndrome, and MOMO syndrome. (The term "non-syndromic obesity" is sometimes used to exclude these conditions.)[141] In people with early-onset severe obesity (defined by an onset before 10 years of age and body mass index over three standard deviations above normal), 7% harbor a single point DNA mutation.[142]
Studies that have focused on inheritance patterns rather than on specific genes have found that 80% of the offspring of two obese parents were also obese, in contrast to less than 10% of the offspring of two parents who were of normal weight.[143] Different people exposed to the same environment have different risks of obesity due to their underlying genetics.[144]
The thrifty gene hypothesis postulates that, due to dietary scarcity during human evolution, people are prone to obesity. Their ability to take advantage of rare periods of abundance by storing energy as fat would be advantageous during times of varying food availability, and individuals with greater adipose reserves would be more likely to survive famine. This tendency to store fat, however, would be maladaptive in societies with stable food supplies.[medical citation needed] This theory has received various criticisms, and other evolutionarily-based theories such as the drifty gene hypothesis and the thrifty phenotype hypothesis have also been proposed.[medical citation needed]
Other illnesses
Certain physical and mental illnesses and the pharmaceutical substances used to treat them can increase risk of obesity. Medical illnesses that increase obesity risk include several rare genetic syndromes (listed above) as well as some congenital or acquired conditions: hypothyroidism, Cushing's syndrome, growth hormone deficiency,[145] and some eating disorders such as binge eating disorder and night eating syndrome.[2] However, obesity is not regarded as a psychiatric disorder, and therefore is not listed in the DSM-IVR as a psychiatric illness.[146] The risk of overweight and obesity is higher in patients with psychiatric disorders than in persons without psychiatric disorders.[147] Obesity and depression influence each other mutually, with obesity increasing the risk of clinical depression, and also depression leading to a higher chance of developing obesity.[3]
Drug-induced obesity
Certain medications may cause weight gain or changes in body composition; these include insulin, sulfonylureas, thiazolidinediones, atypical antipsychotics, antidepressants, steroids, certain anticonvulsants (phenytoin and valproate), pizotifen, and some forms of hormonal contraception.[2]
Social determinants
Main article: Social determinants of obesity
The disease scroll (Yamai no soshi, late 12th century) depicts a woman moneylender with obesity, considered a disease of the rich.
Obesity in developed countries is correlated with economic inequality.
While genetic influences are important to understanding obesity, they cannot completely explain the dramatic increase seen within specific countries or globally.[148][better source needed] Though it is accepted that energy consumption in excess of energy expenditure leads to increases in body weight on an individual basis, the cause of the shifts in these two factors on the societal scale is much debated. There are a number of theories as to the cause but most believe it is a combination of various factors.
The correlation between social class and BMI varies globally. Research in 1989 found that in developed countries women of a high social class were less likely to be obese. No significant differences were seen among men of different social classes. In the developing world, women, men, and children from high social classes had greater rates of obesity.[better source needed][149] In 2007 repeating the same research found the same relationships, but they were weaker. The decrease in strength of correlation was felt to be due to the effects of globalization.[150] Among developed countries, levels of adult obesity, and percentage of teenage children who are overweight, are correlated with income inequality. A similar relationship is seen among US states: more adults, even in higher social classes, are obese in more unequal states.[151]
Many explanations have been put forth for associations between BMI and social class. It is thought that in developed countries, the wealthy are able to afford more nutritious food, they are under greater social pressure to remain slim, and have more opportunities along with greater expectations for physical fitness. In undeveloped countries the ability to afford food, high energy expenditure with physical labor, and cultural values favoring a larger body size are believed to contribute to the observed patterns.[150] Attitudes toward body weight held by people in one's life may also play a role in obesity. A correlation in BMI changes over time has been found among friends, siblings, and spouses.[152] Stress and perceived low social status appear to increase risk of obesity.[151][153][154]
Smoking has a significant effect on an individual's weight. Those who quit smoking gain an average of 4.4 kilograms (9.7 lb) for men and 5.0 kilograms (11.0 lb) for women over ten years.[155] However, changing rates of smoking have had little effect on the overall rates of obesity.[156]
In the United States, the number of children a person has is related to their risk of obesity. A woman's risk increases by 7% per child, while a man's risk increases by 4% per child.[157] This could be partly explained by the fact that having dependent children decreases physical activity in Western parents.[158]
In the developing world urbanization is playing a role in increasing rate of obesity. In China overall rates of obesity are below 5%; however, in some cities rates of obesity are greater than 20%.[159] In part, this may be because of urban design issues (such as inadequate public spaces for physical activity).[128] Time spent in motor vehicles, as opposed to active transportation options such as cycling or walking, is correlated with increased risk of obesity.[160][161]
Malnutrition in early life is believed to play a role in the rising rates of obesity in the developing world.[162] Endocrine changes that occur during periods of malnutrition may promote the storage of fat once more food energy becomes available.[162]
Gut bacteria
See also: Infectobesity
The study of the effect of infectious agents on metabolism is still in its early stages. Gut flora has been shown to differ between lean and obese people. There is an indication that gut flora can affect the metabolic potential. This apparent alteration is believed to confer a greater capacity to harvest energy contributing to obesity. Whether these differences are the direct cause or the result of obesity has yet to be determined unequivocally.[163] The use of antibiotics among children has also been associated with obesity later in life.[164][165]
An association between viruses and obesity has been found in humans and several different animal species. The amount that these associations may have contributed to the rising rate of obesity is yet to be determined.[166]
Other factors
Not getting enough sleep is also associated with obesity.[167][168] Whether one causes the other is unclear.[167] Even if short sleep does increase weight gain, it is unclear if this is to a meaningful degree or if increasing sleep would be of benefit.[169]
Some have proposed that chemical compounds called "obesogens" may play a role in obesity.
Certain aspects of personality are associated with being obese.[170] Loneliness,[171] neuroticism, impulsivity, and sensitivity to reward are more common in people who are obese while conscientiousness and self-control are less common in people who are obese.[170][172] Because most of the studies on this topic are questionnaire-based, it is possible that these findings overestimate the relationships between personality and obesity: people who are obese might be aware of the social stigma of obesity and their questionnaire responses might be biased accordingly.[170] Similarly, the personalities of people who are obese as children might be influenced by obesity stigma, rather than these personality factors acting as risk factors for obesity.[170]
In relation to globalization, it is known that trade liberalization is linked to obesity; research, based on data from 175 countries during 1975-2016, showed that obesity prevalence was positively correlated with trade openness, and the correlation was stronger in developing countries.[173]
Pathophysiology
Main article: Pathophysiology of obesity
Two white mice both with similar sized ears, black eyes, and pink noses. The body of the mouse on the left, however, is about three times the width of the normal sized mouse on the right.
A comparison of a mouse unable to produce leptin thus resulting in obesity (left) and a normal mouse (right)
Two distinct but related processes are considered to be involved in the development of obesity: sustained positive energy balance (energy intake exceeding energy expenditure) and the resetting of the body weight "set point" at an increased value.[174] The second process explains why finding effective obesity treatments has been difficult. While the underlying biology of this process still remains uncertain, research is beginning to clarify the mechanisms.[174]
At a biological level, there are many possible pathophysiological mechanisms involved in the development and maintenance of obesity.[175] This field of research had been almost unapproached until the leptin gene was discovered in 1994 by J. M. Friedman's laboratory.[176] While leptin and ghrelin are produced peripherally, they control appetite through their actions on the central nervous system. In particular, they and other appetite-related hormones act on the hypothalamus, a region of the brain central to the regulation of food intake and energy expenditure. There are several circuits within the hypothalamus that contribute to its role in integrating appetite, the melanocortin pathway being the most well understood.[175] The circuit begins with an area of the hypothalamus, the arcuate nucleus, that has outputs to the lateral hypothalamus (LH) and ventromedial hypothalamus (VMH), the brain's feeding and satiety centers, respectively.[177]
The arcuate nucleus contains two distinct groups of neurons.[175] The first group coexpresses neuropeptide Y (NPY) and agouti-related peptide (AgRP) and has stimulatory inputs to the LH and inhibitory inputs to the VMH. The second group coexpresses pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) and has stimulatory inputs to the VMH and inhibitory inputs to the LH. Consequently, NPY/AgRP neurons stimulate feeding and inhibit satiety, while POMC/CART neurons stimulate satiety and inhibit feeding. Both groups of arcuate nucleus neurons are regulated in part by leptin. Leptin inhibits the NPY/AgRP group while stimulating the POMC/CART group. Thus a deficiency in leptin signaling, either via leptin deficiency or leptin resistance, leads to overfeeding and may account for some genetic and acquired forms of obesity.[175]
Management
Main article: Management of obesity
The main treatment for obesity consists of weight loss via lifestyle interventions, including prescribed diets and physical exercise.[22][96][178][179] Although it is unclear what diets might support long-term weight loss, and although the effectiveness of low-calorie diets is debated,[180] lifestyle changes that reduce calorie consumption or increase physical exercise over the long term also tend to produce some sustained weight loss, despite slow weight regain over time.[22][180][181][182] Although 87% of participants in the National Weight Control Registry were able to maintain 10% body weight loss for 10 years,[183][clarification needed] the most appropriate dietary approach for long term weight loss maintenance is still unknown.[184] In the US, intensive behavioral interventions combining both dietary changes and exercise are recommended.[22][178][185] Intermittent fasting has no additional benefit of weight loss compared to continuous energy restriction.[184] Adherence is a more important factor in weight loss success than whatever kind of diet an individual undertakes.[184][186]
Several hypo-caloric diets are effective.[22] In the short-term low carbohydrate diets appear better than low fat diets for weight loss.[187] In the long term, however, all types of low-carbohydrate and low-fat diets appear equally beneficial.[187][188] Heart disease and diabetes risks associated with different diets appear to be similar.[189] Promotion of the Mediterranean diets among the obese may lower the risk of heart disease.[187] Decreased intake of sweet drinks is also related to weight-loss.[187] Success rates of long-term weight loss maintenance with lifestyle changes are low, ranging from 2–20%.[190] Dietary and lifestyle changes are effective in limiting excessive weight gain in pregnancy and improve outcomes for both the mother and the child.[191] Intensive behavioral counseling is recommended in those who are both obese and have other risk factors for heart disease.[192]
Health policy
Prevalence of obesity in the adult population, top countries (2016)
Prevalence of obesity in the adult population in 2016
Obesity is a complex public health and policy problem because of its prevalence, costs, and health effects.[193] As such, managing it requires changes in the wider societal context and effort by communities, local authorities, and governments.[185] Public health efforts seek to understand and correct the environmental factors responsible for the increasing prevalence of obesity in the population. Solutions look at changing the factors that cause excess food energy consumption and inhibit physical activity. Efforts include federally reimbursed meal programs in schools, limiting direct junk food marketing to children,[194] and decreasing access to sugar-sweetened beverages in schools.[195] The World Health Organization recommends the taxing of sugary drinks.[196] When constructing urban environments, efforts have been made to increase access to parks and to develop pedestrian routes.[197]
Mass media campaigns seem to have limited effectiveness in changing behaviors that influence obesity, but may increase knowledge and awareness regarding physical activity and diet, which might lead to changes in the long term. Campaigns might also be able to reduce the amount of time spent sitting or lying down and positively affect the intention to be active physically.[198][199] Nutritional labelling with energy information on menus might be able to help reducing energy intake while dining in restaurants.[200] Some call for policy against ultra-processed foods.[201][202]
Medical interventions
Medication
Main article: Anti-obesity medication
Since the introduction of medicines for the management of obesity in the 1930s, many compounds have been tried. Most of them reduce body weight by small amounts, and several of them are no longer marketed for obesity because of their side effects. Out of 25 anti-obesity medications withdrawn from the market between 1964 and 2009, 23 acted by altering the functions of chemical neurotransmitters in the brain. The most common side effects of these drugs that led to withdrawals were mental disturbances, cardiac side effects, and drug abuse or drug dependence. Deaths were reportedly associated with seven products.[203]
Five medications beneficial for long-term use are: orlistat, lorcaserin, liraglutide, phentermine–topiramate, and naltrexone–bupropion.[204] They result in weight loss after one year ranged from 3.0 to 6.7 kg (6.6-14.8 lbs) over placebo.[204] Orlistat, liraglutide, and naltrexone–bupropion are available in both the United States and Europe, phentermine–topiramate is available only in the United States.[205] European regulatory authorities rejected lorcaserin and phentermine-topiramate, in part because of associations of heart valve problems with lorcaserin and more general heart and blood vessel problems with phentermine–topiramate.[205] Lorcaserin was available in the United States and then removed from the market in 2020 due to its association with cancer.[206] Orlistat use is associated with high rates of gastrointestinal side effects[207] and concerns have been raised about negative effects on the kidneys.[208] There is no information on how these drugs affect longer-term complications of obesity such as cardiovascular disease or death;[5] however, liraglutide, when used for type 2 diabetes, does reduce cardiovascular events.[209]
In 2019 a systematic review compared the effects on weight of various doses of fluoxetine (60 mg/d, 40 mg/d, 20 mg/d, 10 mg/d) in obese adults.[210] When compared to placebo, all dosages of fluoxetine appeared to contribute to weight loss but lead to increased risk of experiencing side effects such as dizziness, drowsiness, fatigue, insomnia and nausea during period of treatment. However, these conclusions were from low certainty evidence.[210] When comparing, in the same review, the effects of fluoxetine on weight of obese adults, to other anti-obesity agents, omega-3 gel and not receiving a treatment, the authors could not reach conclusive results due to poor quality of evidence.[210]
Among antipsychotic drugs for treating schizophrenia clozapine is the most effective, but it also has the highest risk of causing the metabolic syndrome, of which obesity is the main feature. For people who gain weight because of clozapine, taking metformin may reportedly improve three of the five components of the metabolic syndrome: waist circumference, fasting glucose, and fasting triglycerides.[211]
Surgery
The most effective treatment for obesity is bariatric surgery.[6][22] The types of procedures include laparoscopic adjustable gastric banding, Roux-en-Y gastric bypass, vertical-sleeve gastrectomy, and biliopancreatic diversion.[204] Surgery for severe obesity is associated with long-term weight loss, improvement in obesity-related conditions,[212] and decreased overall mortality; however, improved metabolic health results from the weight loss, not the surgery.[213] One study found a weight loss of between 14% and 25% (depending on the type of procedure performed) at 10 years, and a 29% reduction in all cause mortality when compared to standard weight loss measures.[214] Complications occur in about 17% of cases and reoperation is needed in 7% of cases.[212]
Epidemiology
Main article: Epidemiology of obesity
Share of adults with BMIs > 30 (2022)
Graphs are unavailable due to technical issues. There is more info on Phabricator and on MediaWiki.org.
See or edit source data.
In earlier historical periods obesity was rare and achievable only by a small elite, although already recognised as a problem for health. But as prosperity increased in the Early Modern period, it affected increasingly larger groups of the population.[215] Prior to the 1970s, obesity was a relatively rare condition even in the wealthiest of nations, and when it did exist it tended to occur among the wealthy. Then, a confluence of events started to change the human condition. The average BMI of populations in first-world countries started to increase, and consequently there was a rapid increase in the proportion of people overweight and obese.[216]
In 1997, the WHO formally recognized obesity as a global epidemic.[114] As of 2008, the WHO estimates that at least 500 million adults (greater than 10%) are obese, with higher rates among women than men.[217] The global prevalence of obesity more than doubled between 1980 and 2014. In 2014, more than 600 million adults were obese, equal to about 13 percent of the world's adult population.[218] The percentage of adults affected in the United States as of 2015–2016 is about 39.6% overall (37.9% of males and 41.1% of females).[219] In 2000, the World Health Organization (WHO) stated that overweight and obesity were replacing more traditional public health concerns such as undernutrition and infectious diseases as one of the most significant cause of poor health.[220]
The rate of obesity also increases with age at least up to 50 or 60 years old[52]: 5 and severe obesity in the United States, Australia, and Canada is increasing faster than the overall rate of obesity.[30][221][222] The OECD has projected an increase in obesity rates until at least 2030, especially in the United States, Mexico and England with rates reaching 47%, 39% and 35%, respectively.[223]
Once considered a problem only of high-income countries, obesity rates are rising worldwide and affecting both the developed and developing world.[224] These increases have been felt most dramatically in urban settings.[217]
Sex- and gender-based differences also influence the prevalence of obesity. Globally there are more obese women than men, but the numbers differ depending on how obesity is measured.[225][226]
History
Etymology
Obesity is from the Latin obesitas, which means "stout, fat, or plump". Ēsus is the past participle of edere (to eat), with ob (over) added to it.[227] The Oxford English Dictionary documents its first usage in 1611 by Randle Cotgrave.[228]
Historical attitudes
A very obese gentleman with a prominent double chin and mustache dressed in black with a sword at his left side.
During the Middle Ages and the Renaissance The Tuscan General Alessandro del Borro, attributed to Charles Mellin, 1645[229]
A carved stone miniature figurine depicted an obese female.
Venus of Willendorf created 24,000–22,000 BC
Ancient Greek medicine recognizes obesity as a medical disorder and records that the Ancient Egyptians saw it in the same way.[215] Hippocrates wrote that "Corpulence is not only a disease itself, but the harbinger of others".[2] The Indian surgeon Sushruta (6th century BCE) related obesity to diabetes and heart disorders.[230] He recommended physical work to help cure it and its side effects.[230] For most of human history, mankind struggled with food scarcity.[231] Obesity has thus historically been viewed as a sign of wealth and prosperity. It was common among high officials in Ancient East Asian civilizations.[232] In the 17th century, English medical author Tobias Venner is credited with being one of the first to refer to the term as a societal disease in a published English language book.[215][233]
With the onset of the Industrial Revolution, it was realized that the military and economic might of nations were dependent on both the body size and strength of their soldiers and workers.[114] Increasing the average body mass index from what is now considered underweight to what is now the normal range played a significant role in the development of industrialized societies.[114] Height and weight thus both increased through the 19th century in the developed world. During the 20th century, as populations reached their genetic potential for height, weight began increasing much more than height, resulting in obesity.[114] In the 1950s, increasing wealth in the developed world decreased child mortality, but as body weight increased, heart and kidney disease became more common.[114][234] During this time period, insurance companies realized the connection between weight and life expectancy and increased premiums for the obese.[2]
Many cultures throughout history have viewed obesity as the result of a character flaw. The obesus or fat character in Ancient Greek comedy was a glutton and figure of mockery. During Christian times, food was viewed as a gateway to the sins of sloth and lust.[20] In modern Western culture, excess weight is often regarded as unattractive, and obesity is commonly associated with various negative stereotypes. People of all ages can face social stigmatization and may be targeted by bullies or shunned by their peers.[235]
Public perceptions in Western society regarding healthy body weight differ from those regarding the weight that is considered ideal – and both have changed since the beginning of the 20th century. The weight that is viewed as an ideal has become lower since the 1920s. This is illustrated by the fact that the average height of Miss America pageant winners increased by 2% from 1922 to 1999, while their average weight decreased by 12%.[236] On the other hand, people's views concerning healthy weight have changed in the opposite direction. In Britain, the weight at which people considered themselves to be overweight was significantly higher in 2007 than in 1999.[237] These changes are believed to be due to increasing rates of adiposity leading to increased acceptance of extra body fat as being normal.[237]
Obesity is still seen as a sign of wealth and well-being in many parts of Africa. This has become particularly common since the HIV epidemic began.[2]
The arts
The first sculptural representations of the human body 20,000–35,000 years ago depict obese females. Some attribute the Venus figurines to the tendency to emphasize fertility while others feel they represent "fatness" in the people of the time.[20] Corpulence is, however, absent in both Greek and Roman art, probably in keeping with their ideals regarding moderation. This continued through much of Christian European history, with only those of low socioeconomic status being depicted as obese.[20]
During the Renaissance some of the upper class began flaunting their large size, as can be seen in portraits of Henry VIII of England and Alessandro dal Borro.[20] Rubens (1577–1640) regularly depicted heavyset women in his pictures, from which derives the term Rubenesque. These women, however, still maintained the "hourglass" shape with its relationship to fertility.[238] During the 19th century, views on obesity changed in the Western world. After centuries of obesity being synonymous with wealth and social status, slimness began to be seen as the desirable standard.[20] In his 1819 print, The Belle Alliance, or the Female Reformers of Blackburn!!!, artist George Cruikshank criticised the work of female reformers in Blackburn and used fatness as a means to portray them as unfeminine.[239]
Society and culture
Economic impact
In addition to its health impacts, obesity leads to many problems, including disadvantages in employment[240]: 29 [241] and increased business costs. These effects are felt by all levels of society, from individuals, to corporations, to governments.
In 2005, the medical costs attributable to obesity in the US were an estimated $190.2 billion or 20.6% of all medical expenditures,[242][243][244] while the cost of obesity in Canada was estimated at CA$2 billion in 1997 (2.4% of total health costs).[96] The total annual direct cost of overweight and obesity in Australia in 2005 was A$21 billion. Overweight and obese Australians also received A$35.6 billion in government subsidies.[245] The estimated range for annual expenditures on diet products is $40 billion to $100 billion in the US alone.[246]
The Lancet Commission on Obesity in 2019 called for a global treaty—modelled on the WHO Framework Convention on Tobacco Control—committing countries to address obesity and undernutrition, explicitly excluding the food industry from policy development. They estimate the global cost of obesity $2 trillion a year, about or 2.8% of world GDP.[247]
Obesity prevention programs have been found to reduce the cost of treating obesity-related disease. However, the longer people live, the more medical costs they incur. Researchers, therefore, conclude that reducing obesity may improve the public's health, but it is unlikely to reduce overall health spending.[248] Sin taxes such as a sugary drink tax have been implemented in certain countries globally to curb dietary and consumer habits, and as an effort to offset the economic tolls.
An extra wide chair beside a number of normal sized chairs.
Services accommodate obese people with specialized equipment such as much wider chairs.[249]
Obesity can lead to social stigmatization and disadvantages in employment.[240]: 29 When compared to their normal weight counterparts, obese workers on average have higher rates of absenteeism from work and take more disability leave, thus increasing costs for employers and decreasing productivity.[250] A study examining Duke University employees found that people with a BMI over 40 kg/m2 filed twice as many workers' compensation claims as those whose BMI was 18.5–24.9 kg/m2. They also had more than 12 times as many lost work days. The most common injuries in this group were due to falls and lifting, thus affecting the lower extremities, wrists or hands, and backs.[251] The Alabama State Employees' Insurance Board approved a controversial plan to charge obese workers $25 a month for health insurance that would otherwise be free unless they take steps to lose weight and improve their health. These measures started in January 2010 and apply to those state workers whose BMI exceeds 35 kg/m2 and who fail to make improvements in their health after one year.[252]
Some research shows that obese people are less likely to be hired for a job and are less likely to be promoted.[235] Obese people are also paid less than their non-obese counterparts for an equivalent job; obese women on average make 6% less and obese men make 3% less.[240]: 30
Specific industries, such as the airline, healthcare and food industries, have special concerns. Due to rising rates of obesity, airlines face higher fuel costs and pressures to increase seating width.[253] In 2000, the extra weight of obese passengers cost airlines US$275 million.[254] The healthcare industry has had to invest in special facilities for handling severely obese patients, including special lifting equipment and bariatric ambulances.[255] Costs for restaurants are increased by litigation accusing them of causing obesity.[256] In 2005, the US Congress discussed legislation to prevent civil lawsuits against the food industry in relation to obesity; however, it did not become law.[256]
With the American Medical Association's 2013 classification of obesity as a chronic disease,[23] it is thought that health insurance companies will more likely pay for obesity treatment, counseling and surgery, and the cost of research and development of fat treatment pills or gene therapy treatments should be more affordable if insurers help to subsidize their cost.[257] The AMA classification is not legally binding, however, so health insurers still have the right to reject coverage for a treatment or procedure.[257]
In 2014, The European Court of Justice ruled that morbid obesity is a disability. The Court said that if an employee's obesity prevents them from "full and effective participation of that person in professional life on an equal basis with other workers", then it shall be considered a disability and that firing someone on such grounds is discriminatory.[258]
In low-income countries, obesity can be a signal of wealth. A 2023 experimental study found that obese individuals in Uganda were more likely to access credit.[259]
Size acceptance
See also: Fat acceptance movement, Social stigma of obesity, Health at Every Size, and Fat fetishism
United States President William Howard Taft was often ridiculed for being overweight.
German politician Ricarda Lang is a victim of fat shaming on the internet.[260]
The principal goal of the fat acceptance movement is to decrease discrimination against people who are overweight and obese.[261][262] However, some in the movement are also attempting to challenge the established relationship between obesity and negative health outcomes.[263]
A number of organizations exist that promote the acceptance of obesity. They have increased in prominence in the latter half of the 20th century.[264] The US-based National Association to Advance Fat Acceptance (NAAFA) was formed in 1969 and describes itself as a civil rights organization dedicated to ending size discrimination.[265]
The International Size Acceptance Association (ISAA) is a non-governmental organization (NGO) which was founded in 1997. It has more of a global orientation and describes its mission as promoting size acceptance and helping to end weight-based discrimination.[266] These groups often argue for the recognition of obesity as a disability under the US Americans With Disabilities Act (ADA). The American legal system, however, has decided that the potential public health costs exceed the benefits of extending this anti-discrimination law to cover obesity.[263]
Industry influence on research
In 2015, the New York Times published an article on the Global Energy Balance Network, a nonprofit founded in 2014 that advocated for people to focus on increasing exercise rather than reducing calorie intake to avoid obesity and to be healthy. The organization was founded with at least $1.5M in funding from the Coca-Cola Company, and the company has provided $4M in research funding to the two founding scientists Gregory A. Hand and Steven N. Blair since 2008.[267][268]
Reports
Many organizations have published reports pertaining to obesity. In 1998, the first US Federal guidelines were published, titled "Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report".[269] In 2006, the Canadian Obesity Network, now known as Obesity Canada published the "Canadian Clinical Practice Guidelines (CPG) on the Management and Prevention of Obesity in Adults and Children". This is a comprehensive evidence-based guideline to address the management and prevention of overweight and obesity in adults and children.[96]
In 2004, the United Kingdom Royal College of Physicians, the Faculty of Public Health and the Royal College of Paediatrics and Child Health released the report "Storing up Problems", which highlighted the growing problem of obesity in the UK.[270] The same year, the House of Commons Health Select Committee published its "most comprehensive inquiry [...] ever undertaken" into the impact of obesity on health and society in the UK and possible approaches to the problem.[271] In 2006, the National Institute for Health and Clinical Excellence (NICE) issued a guideline on the diagnosis and management of obesity, as well as policy implications for non-healthcare organizations such as local councils.[272] A 2007 report produced by Derek Wanless for the King's Fund warned that unless further action was taken, obesity had the capacity to debilitate the National Health Service financially.[273] In 2022 the National Institute for Health and Care Research (NIHR) published a comprehensive review of research on what local authorities can do to reduce obesity.[199]
The Obesity Policy Action (OPA) framework divides measure into upstream policies, midstream policies, and downstream policies. Upstream policies have to do with changing society, while midstream policies try to alter behaviors believed to contribute to obesity at the individual level, while downstream policies treat currently obese people.[274]
Childhood obesity
Main article: Childhood obesity
The healthy BMI range varies with the age and sex of the child. Obesity in children and adolescents is defined as a BMI greater than the 95th percentile.[275] The reference data that these percentiles are based on is from 1963 to 1994 and thus has not been affected by the recent increases in rates of obesity.[276] Childhood obesity has reached epidemic proportions in the 21st century, with rising rates in both the developed and the developing world. Rates of obesity in Canadian boys have increased from 11% in the 1980s to over 30% in the 1990s, while during this same time period rates increased from 4 to 14% in Brazilian children.[277] In the UK, there were 60% more obese children in 2005 compared to 1989.[278] In the US, the percentage of overweight and obese children increased to 16% in 2008, a 300% increase over the prior 30 years.[279]
As with obesity in adults, many factors contribute to the rising rates of childhood obesity. Changing diet and decreasing physical activity are believed to be the two most important causes for the recent increase in the incidence of child obesity.[280] Advertising of unhealthy foods to children also contributes, as it increases their consumption of the product.[281] Antibiotics in the first 6 months of life have been associated with excess weight at age seven to twelve years of age.[165] Because childhood obesity often persists into adulthood and is associated with numerous chronic illnesses, children who are obese are often tested for hypertension, diabetes, hyperlipidemia, and fatty liver disease.[96]
Treatments used in children are primarily lifestyle interventions and behavioral techniques, although efforts to increase activity in children have had little success.[282] In the United States, medications are not FDA approved for use in this age group.[277] Brief weight management interventions in primary care (e.g. delivered by a physician or nurse practitioner) have only a marginal positive effect in reducing childhood overweight or obesity.[283] Multi-component behaviour change interventions that include changes to dietary and physical activity may reduce BMI in the short term in children aged 6 to 11 years, although the benefits are small and quality of evidence is low.[284]
Other animals
Neolife Potential Side Effects
NeoLife offers a range of health and nutritional supplements designed to address various health needs. While generally considered safe when used as directed, some side effects and precautions are associated with their products:
1. **General Considerations**: NeoLife products, like other supplements, should not replace a balanced diet. They are intended to fill nutritional gaps and provide additional nutrients
2. **Potential Side Effects**:
- **Allergic Reactions**: Some users might experience allergic reactions, especially if they are sensitive to specific ingredients like herbs, vitamins, or minerals found in the products.
- **Digestive Issues**: Supplements such as high-dose vitamins or minerals can sometimes cause gastrointestinal discomfort, including nausea, diarrhea, or constipation【
- **Herbal Supplements**: Products containing herbs (e.g., NeoLife's Feminine Herbal Complex) may cause mild side effects like gastrointestinal upset or allergic reactions in some individuals
3. **Specific Products**:
- **Cal-Mag with Vitamin D3**: Generally well-tolerated, but high doses of calcium can lead to kidney stones in susceptible individuals. Vitamin D toxicity is rare but possible if taken in excessive amounts
- **Fibre Tablets**: May cause bloating or gas initially as the body adjusts to increased fiber intake
- **Full Motion (Glucosamine Supplement)**: Generally safe but may cause mild side effects such as stomach upset or allergic reactions, particularly in individuals with shellfish allergies, since glucosamine is often derived from shellfish
4. **Safety and Efficacy**: NeoLife emphasizes the quality and purity of their ingredients, adhering to strict manufacturing standards. However, it is always advisable to consult with a healthcare professional before starting any new supplement, especially for individuals with preexisting health conditions or those taking other medications
For those considering NeoLife products, consulting with a healthcare provider can ensure safe and appropriate use tailored to individual health needs.
### Understanding NeoLife's Compensation Plan: How NeoLife Pays Its Distributors
NeoLife, a global health and wellness company, offers a unique business opportunity through its compensation plan, which rewards distributors for their sales efforts and leadership skills. This multi-level marketing (MLM) plan provides multiple avenues for earning income, making it an attractive option for individuals looking to build a business in the health and nutrition industry. Let's explore the various ways NeoLife compensates its distributors.
#### 1. **Retail Profit**
The most straightforward way to earn with NeoLife is through retail profit. Distributors purchase products at wholesale prices and sell them at retail prices, pocketing the difference. This direct profit margin is an immediate source of income and can be a significant revenue stream, especially for those with a strong customer base.
#### 2. **Sales Volume Bonus**
NeoLife offers a Sales Volume Bonus (SVB) to distributors based on their monthly sales volume. The more products a distributor sells, the higher their bonus. This bonus is calculated as a percentage of the total sales volume, encouraging distributors to boost their sales efforts continuously.
#### 3. **Personal Sales Bonus**
Distributors can earn a Personal Sales Bonus when they achieve certain sales targets. This bonus rewards individuals for their personal selling activities and is an excellent way to increase earnings by focusing on direct sales to customers.
#### 4. **Team Building Bonus**
NeoLife's compensation plan emphasizes team building and leadership. Distributors earn a Team Building Bonus by recruiting new distributors and helping them succeed. This bonus is paid on the sales volume generated by their downline (the distributors they have recruited). The more successful the downline, the higher the earnings for the recruiter.
#### 5. **Leadership Development Bonus**
The Leadership Development Bonus is designed to reward distributors who develop leaders within their team. As distributors advance to higher ranks and help their downline do the same, they earn additional bonuses. This aspect of the compensation plan ensures that experienced distributors are motivated to mentor and support new recruits, fostering a collaborative environment.
#### 6. **Director and Above Bonuses**
For those who reach the rank of Director and above, NeoLife offers substantial bonuses. Directors and higher-ranked distributors receive a percentage of the total company sales, providing significant earning potential. These bonuses are designed to reward top performers and are a testament to the potential of a NeoLife business.
#### 7. **Lifestyle Bonuses and Incentives**
NeoLife also offers lifestyle bonuses and incentives, including trips, cars, and other rewards. These are given to distributors who meet specific sales and recruitment targets. These incentives add an exciting dimension to the business opportunity, motivating distributors to aim higher and achieve more.
#### 8. Residual Income
One of the most attractive features of NeoLife's compensation plan is the potential for residual income. As distributors build a robust customer base and a successful team, they continue to earn commissions on sales made by their downline, even if they are not directly involved in those sales. This ongoing income can provide long-term financial stability and is a key benefit of the MLM model.
### Conclusion
NeoLife’s compensation plan is designed to be both lucrative and motivational, offering multiple income streams and substantial bonuses for those who are dedicated and effective in their sales and leadership efforts. By focusing on both direct sales and team development, distributors can build a sustainable and profitable business. Whether you're looking to earn extra income or build a full-time career, NeoLife provides a comprehensive and rewarding business opportunity.
### Jerry Brassfield: The Visionary Behind NeoLife
Jerry Brassfield is the driving force and visionary behind NeoLife, a global health and wellness company committed to improving lives through superior nutrition products. Brassfield's journey from humble beginnings to becoming a prominent figure in the health and wellness industry is a testament to his entrepreneurial spirit, commitment to quality, and dedication to helping others achieve their best health.
#### Early Life and Inspiration
Jerry Brassfield's story begins in the small town of Oroville, California, where he was born in 1940. Growing up in a modest family, Brassfield faced numerous health challenges as a child, including severe asthma and allergies. His mother's quest to find natural remedies for his ailments sparked Brassfield's lifelong interest in nutrition and health. This personal experience with the transformative power of nutrition laid the foundation for his future endeavors.
#### The Birth of NeoLife
In 1958, at the young age of 19, Brassfield founded NeoLife, initially called Golden Products. His mission was to provide high-quality nutritional supplements that could help others achieve optimal health, just as they had for him. Brassfield's approach was groundbreaking: he combined the principles of nature with the latest scientific research to create products that were not only effective but also safe and natural.
#### Commitment to Quality and Science
Under Brassfield's leadership, NeoLife has always prioritized quality and scientific rigor. The company's products are developed based on the highest standards of research, involving leading scientists and nutrition experts. This commitment is evident in NeoLife's Scientific Advisory Board, which ensures that all products are backed by solid scientific evidence and adhere to the strictest quality controls.
#### Building a Global Network
Jerry Brassfield's vision extended beyond creating superior products; he also wanted to empower people to build their own businesses and improve their lives. Through a multi-level marketing (MLM) model, NeoLife provides individuals with the opportunity to become distributors and share the benefits of NeoLife products with others. This business model has helped NeoLife grow into a global network, spanning over 50 countries and positively impacting countless lives.
#### Philanthropy and Giving Back
Brassfield's success has not diminished his commitment to giving back. He is actively involved in various philanthropic endeavors, focusing on health, education, and community development. The NeoLife Foundation, established by Brassfield, supports numerous charitable initiatives, including providing nutritional support to underserved communities and funding educational programs.
#### Personal Values and Leadership Style
Jerry Brassfield is known for his hands-on leadership style and his unwavering commitment to integrity and excellence. He believes in leading by example, and his personal values are deeply ingrained in NeoLife's corporate culture. Brassfield's emphasis on family, health, and personal development resonates throughout the organization, fostering a supportive and inspiring environment for distributors and employees alike.
#### Legacy and Future Vision
As NeoLife continues to grow and evolve, Jerry Brassfield remains at the helm, guiding the company with his visionary leadership. His legacy is not just in the products NeoLife offers but in the lives it transforms through improved health and the opportunity for financial independence. Brassfield's dedication to innovation and his relentless pursuit of excellence ensure that NeoLife will continue to be a leader in the health and wellness industry for years to come.
### Conclusion
Jerry Brassfield's journey from a young boy struggling with health issues to the founder of a global health and wellness company is a remarkable story of vision, perseverance, and passion. Through NeoLife, Brassfield has not only provided superior nutritional products but has also empowered thousands of individuals to achieve better health and financial freedom. His enduring commitment to quality, science, and helping others serves as an inspiration and a testament to what can be achieved with dedication and a clear vision.
guide on overcoming addiction:
### Outline: Overcoming Addiction
1. **Introduction**
- Definition of Addiction
- Types of Addiction (Substance, Behavioral)
- Importance of Addressing Addiction
- Overview of the Guide
2. **Understanding Addiction**
- The Science of Addiction: Brain Chemistry and Pathways
- Psychological Aspects of Addiction
- Social and Environmental Factors
- Genetic Predisposition and Risk Factors
- Signs and Symptoms of Addiction
3. **Recognizing the Problem**
- Self-Assessment: Identifying Addiction in Yourself
- How to Recognize Addiction in Others
- Denial and Resistance to Acknowledging Addiction
- The Role of Intervention
4. **Deciding to Change**
- The Stages of Change Model (Precontemplation, Contemplation, Preparation, Action, Maintenance)
- Overcoming Ambivalence
- Setting Realistic Goals
- The Importance of Motivation and Commitment
5. **Seeking Help**
- Types of Treatment Options (Inpatient, Outpatient, Therapy, Support Groups)
- How to Choose the Right Treatment Program
- The Role of Healthcare Professionals (Doctors, Therapists, Counselors)
- How to Find Support Networks (Friends, Family, Community Resources)
6. **Detoxification and Withdrawal**
- Understanding the Detox Process
- Managing Withdrawal Symptoms
- Medical Supervision and Support during Detox
- Post-Detox Care and Planning
7. **Therapies and Treatment Approaches**
- Cognitive Behavioral Therapy (CBT)
- Dialectical Behavior Therapy (DBT)
- Motivational Interviewing (MI)
- 12-Step Programs (AA, NA)
- Alternative Therapies (Mindfulness, Yoga, Art Therapy)
8. **Building a Support System**
- The Role of Family and Friends in Recovery
- How to Communicate with Loved Ones about Addiction
- Building a Sober Network
- Joining Support Groups (SMART Recovery, Refuge Recovery)
9. **Lifestyle Changes**
- The Importance of Routine and Structure
- Healthy Habits (Nutrition, Exercise, Sleep)
- Finding New Hobbies and Interests
- Avoiding Triggers and High-Risk Situations
10. **Relapse Prevention**
- Understanding Relapse as Part of Recovery
- Identifying Triggers and Warning Signs
- Developing Coping Strategies
- Building Resilience and Emotional Strength
11. **Long-Term Recovery**
- Maintaining Motivation and Commitment
- Continuing Therapy and Support
- Setting Long-Term Goals and Celebrating Milestones
- Giving Back: Helping Others in Their Recovery Journey
12. **Personal Stories and Testimonials**
- Success Stories of Overcoming Addiction
- Learning from Others’ Experiences
- The Power of Sharing Your Story
13. **Resources and Further Reading**
- Books and Articles on Addiction and Recovery
- Online Resources and Support Groups
- Contact Information for Support Services and Hotlines
14. **Conclusion**
- Recap of Key Points
- Encouragement and Final Words of Support
- The Ongoing Journey of Recovery
### Detailed Content (Sample)
### Introduction
#### Definition of Addiction
Addiction is a complex, chronic disease characterized by compulsive substance use or engagement in a behavior despite harmful consequences. It affects the brain's reward, motivation, and memory functions, making it difficult for individuals to resist the urge to engage in the addictive behavior or substance use.
#### Types of Addiction
Addiction can be broadly categorized into two types:
1. **Substance Addiction**: Involves the abuse of drugs or alcohol. Examples include alcoholism, opioid addiction, and nicotine dependence.
2. **Behavioral Addiction**: Involves compulsive behaviors that do not involve substance use but have similar effects on the brain. Examples include gambling addiction, internet addiction, and shopping addiction.
#### Importance of Addressing Addiction
Addressing addiction is crucial for several reasons:
- **Health**: Addiction can lead to severe physical and mental health issues, including heart disease, liver damage, anxiety, and depression.
- **Relationships**: It can strain or destroy personal relationships with family, friends, and colleagues.
- **Society**: Addiction can result in significant social and economic costs, including lost productivity, increased healthcare costs, and higher rates of crime.
- **Personal Fulfillment**: Overcoming addiction allows individuals to regain control of their lives, pursue their goals, and achieve personal fulfillment.
#### Overview of the Guide
This guide aims to provide comprehensive information and practical advice on overcoming addiction. It covers the science behind addiction, steps to recognize and address it, various treatment options, and strategies for long-term recovery. Whether you are struggling with addiction yourself or supporting someone who is, this guide offers valuable insights and resources to help navigate the journey to recovery.
### Understanding Addiction
#### The Science of Addiction: Brain Chemistry and Pathways
Addiction fundamentally alters the brain's structure and function. Key areas affected include:
- **The Reward System**: Addictive substances or behaviors stimulate the release of dopamine, a neurotransmitter associated with pleasure and reward. Over time, the brain becomes reliant on these stimuli to release dopamine, leading to cravings and compulsive behavior.
- **Prefrontal Cortex**: Responsible for decision-making and impulse control. Addiction impairs its function, making it harder for individuals to make rational decisions and resist urges.
- **Hippocampus and Amygdala**: These areas store memories and emotions related to substance use or addictive behaviors, contributing to cravings and triggers.
#### Psychological Aspects of Addiction
Addiction is not solely a physical condition; psychological factors play a significant role:
- **Coping Mechanism**: Many individuals turn to substances or behaviors as a way to cope with stress, trauma, or mental health issues.
- **Behavioral Patterns**: Addiction can become ingrained in daily routines, making it challenging to break free from the cycle.
- **Emotional Dependence**: Individuals may develop an emotional reliance on the substance or behavior to experience pleasure or avoid pain.
#### Social and Environmental Factors
The environment and social context significantly influence the development and maintenance of addiction:
- **Peer Pressure**: Social circles and peer groups can encourage substance use or addictive behaviors.
- **Accessibility**: Easy access to substances or opportunities for addictive behaviors increases the risk of addiction.
- **Cultural Norms**: Societal attitudes towards substances or behaviors can affect their prevalence and acceptance.
#### Genetic Predisposition and Risk Factors
Research suggests that genetics can play a role in addiction:
- **Hereditary Factors**: Individuals with a family history of addiction are more likely to develop addictive behaviors themselves.
- **Biological Sensitivity**: Genetic variations can affect how the brain responds to substances or behaviors, influencing susceptibility to addiction.
#### Signs and Symptoms of Addiction
Recognizing addiction involves observing changes in behavior, physical health, and emotional well-being:
- **Behavioral Signs**: Increased secrecy, neglect of responsibilities, and changes in social circles.
- **Physical Symptoms**: Withdrawal symptoms, changes in appearance, and health issues related to substance use.
- **Emotional Changes**: Mood swings, irritability, depression, and anxiety.
### Recognizing the Problem
#### Self-Assessment: Identifying Addiction in Yourself
To determine if you might have an addiction, consider the following questions:
- Do you feel a strong urge to use a substance or engage in a behavior regularly?
- Have you tried to cut down or stop without success?
- Do you continue despite knowing the negative consequences?
- Has your addiction affected your relationships, work, or daily life?
#### How to Recognize Addiction in Others
Signs that a loved one might be struggling with addiction include:
- Drastic changes in behavior or personality.
- Unexplained absences or frequent lateness.
- Financial problems or unexplained spending.
- Physical signs such as weight loss, poor hygiene, or track marks.
#### Denial and Resistance to Acknowledging Addiction
Denial is a common barrier to recognizing addiction:
- **Minimizing**: Downplaying the extent of substance use or behavior.
- **Rationalizing**: Justifying addiction as a way to cope with stress or problems.
- **Blaming**: Attributing addiction to external factors rather than personal choice.
#### The Role of Intervention
Interventions can be a crucial step in helping someone acknowledge their addiction:
- **Preparation**: Plan the intervention carefully, involving close family and friends.
- **Execution**: Conduct the intervention in a supportive and non-confrontational manner.
- **Follow-Up**: Be prepared to offer immediate support and options for treatment.
### Deciding to Change
#### The Stages of Change Model
Understanding the stages of change can help individuals navigate the recovery process:
1. **Precontemplation**: Not yet acknowledging the need for change.
2. **Contemplation**: Recognizing the problem but not yet ready to take action.
3. **Preparation**: Making plans and setting goals for change.
4. **Action**: Actively working towards change through treatment and lifestyle adjustments.
5. **Maintenance**: Sustaining changes and preventing relapse.
#### Overcoming Ambivalence
Ambivalence is common when considering change:
- **Pros and Cons**: List the benefits and drawbacks of continuing the addiction versus making a change.
- **Visualize Success**: Imagine a future free from addiction and the positive changes it would bring.
#### Setting Realistic Goals
Goals should
be specific, measurable, achievable, relevant, and time-bound (SMART):
- **Short-Term Goals**: Focus on immediate steps, such as reducing usage or attending a support group.
- **Long-Term Goals**: Aim for sustained recovery, improved health, and restored relationships.
#### The Importance of Motivation and Commitment
Motivation and commitment are key to successful recovery:
- **Intrinsic Motivation**: Focus on personal reasons for wanting to change.
- **Extrinsic Motivation**: Consider external factors, such as family support and societal expectations.
### Seeking Help
#### Types of Treatment Options
Various treatment options cater to different needs and preferences:
- **Inpatient Treatment**: Residential programs providing intensive support and medical supervision.
- **Outpatient Treatment**: Allows individuals to live at home while attending therapy sessions.
- **Therapy**: Includes individual, group, and family therapy to address underlying issues and promote healing.
- **Support Groups**: Peer-led groups offering mutual support and shared experiences.
#### How to Choose the Right Treatment Program
Consider the following when selecting a treatment program:
- **Type of Addiction**: Ensure the program specializes in treating the specific addiction.
- **Level of Care**: Assess the intensity of the program and whether it matches your needs.
- **Accreditation**: Choose programs accredited by reputable organizations.
- **Aftercare Support**: Look for programs that offer ongoing support after treatment.
#### The Role of Healthcare Professionals
Healthcare professionals play a crucial role in recovery:
- **Doctors**: Provide medical supervision during detox and manage withdrawal symptoms.
- **Therapists**: Help address underlying psychological issues and develop coping strategies.
- **Counselors**: Offer support and guidance throughout the recovery process.
#### How to Find Support Networks
Building a support network is essential for sustained recovery:
- **Friends and Family**: Lean on loved ones for encouragement and understanding.
- **Community Resources**: Utilize local resources, such as community centers and non-profits.
- **Online Support**: Join online forums and groups for additional support and connection.
### Detoxification and Withdrawal
#### Understanding the Detox Process
Detoxification is the first step in overcoming physical dependence:
- **Medical Detox**: Supervised by healthcare professionals to manage withdrawal symptoms safely.
- **Natural Detox**: Gradual reduction of substance use under medical advice.
#### Managing Withdrawal Symptoms
Withdrawal can be challenging but manageable with the right support:
- **Medications**: Certain medications can alleviate withdrawal symptoms and cravings.
- **Therapy**: Counseling and support groups help manage the emotional aspects of withdrawal.
- **Healthy Practices**: Hydration, nutrition, and rest are crucial during detox.
#### Medical Supervision and Support during Detox
Medical supervision ensures safety and comfort:
- **Monitoring**: Regular monitoring of vital signs and symptoms.
- **Intervention**: Immediate medical intervention if complications arise.
- **Support**: Emotional and psychological support throughout the process.
#### Post-Detox Care and Planning
Planning for life after detox is crucial for long-term recovery:
- **Continued Therapy**: Ongoing therapy to address psychological aspects of addiction.
- **Support Groups**: Regular attendance at support groups for continued encouragement.
- **Relapse Prevention**: Developing a plan to avoid triggers and manage cravings.
### Therapies and Treatment Approaches
#### Cognitive Behavioral Therapy (CBT)
CBT is effective in treating addiction by addressing thought patterns:
- **Identifying Triggers**: Recognize situations and thoughts that lead to substance use or addictive behaviors.
- **Developing Coping Strategies**: Learn healthy ways to cope with stress and cravings.
- **Changing Behavior**: Replace negative behaviors with positive, healthy alternatives.
#### Dialectical Behavior Therapy (DBT)
DBT combines cognitive and behavioral techniques with mindfulness:
- **Mindfulness**: Focus on the present moment and accept emotions without judgment.
- **Distress Tolerance**: Develop skills to tolerate and manage distressing emotions.
- **Interpersonal Effectiveness**: Improve communication and relationship skills.
- **Emotional Regulation**: Learn to manage and change intense emotions.
#### Motivational Interviewing (MI)
MI helps individuals find their motivation to change:
- **Expressing Empathy**: Therapists build a trusting relationship through empathetic listening.
- **Developing Discrepancy**: Help individuals see the gap between their current behavior and their goals.
- **Rolling with Resistance**: Avoid arguing and instead explore resistance to change.
- **Supporting Self-Efficacy**: Encourage belief in the ability to change.
#### 12-Step Programs
12-step programs offer a structured approach to recovery:
- **Alcoholics Anonymous (AA)**: Focuses on mutual support and the belief in a higher power.
- **Narcotics Anonymous (NA)**: Similar structure to AA but focuses on drug addiction.
- **Steps**: The 12 steps guide individuals through admitting powerlessness, seeking help, and making amends.
#### Alternative Therapies
Alternative therapies can complement traditional treatments:
- **Mindfulness and Meditation**: Promote relaxation and reduce stress.
- **Yoga**: Improves physical health and mental well-being.
- **Art Therapy**: Provides a creative outlet for expressing emotions and healing.
### Building a Support System
#### The Role of Family and Friends in Recovery
Loved ones play a vital role in supporting recovery:
- **Encouragement**: Offer positive reinforcement and celebrate successes.
- **Understanding**: Educate themselves about addiction and recovery.
- **Boundaries**: Set healthy boundaries to protect their well-being while supporting the individual.
#### How to Communicate with Loved Ones about Addiction
Effective communication is key to building a support system:
- **Open Dialogue**: Encourage honest and open conversations about struggles and progress.
- **Active Listening**: Listen without judgment and show empathy.
- **Supportive Language**: Use positive and encouraging language to motivate change.
#### Building a Sober Network
Connecting with others in recovery can provide invaluable support:
- **Support Groups**: Join local or online groups for shared experiences and encouragement.
- **Sober Activities**: Engage in activities that do not involve substance use or addictive behaviors.
- **Mentorship**: Find a mentor or sponsor who can provide guidance and support.
#### Joining Support Groups
Support groups offer a sense of community and accountability:
- **SMART Recovery**: Focuses on self-management and recovery training.
- **Refuge Recovery**: Utilizes Buddhist principles and practices for recovery.
- **LifeRing Secular Recovery**: Emphasizes personal responsibility and peer support.
### Lifestyle Changes
#### The Importance of Routine and Structure
Establishing a routine can provide stability and reduce stress:
- **Daily Schedule**: Plan activities and stick to a consistent daily routine.
- **Time Management**: Allocate time for work, hobbies, exercise, and relaxation.
#### Healthy Habits
Adopting healthy habits supports overall well-being:
- **Nutrition**: Eat a balanced diet to support physical health and mood.
- **Exercise**: Regular physical activity reduces stress and improves mental health.
- **Sleep**: Prioritize good sleep hygiene to ensure adequate rest.
#### Finding New Hobbies and Interests
Engaging in new activities can replace addictive behaviors:
- **Exploration**: Try different hobbies and interests to find what you enjoy.
- **Creativity**: Engage in creative activities such as painting, writing, or playing music.
- **Physical Activities**: Participate in sports, hiking, or other physical pursuits.
#### Avoiding Triggers and High-Risk Situations
Identifying and avoiding triggers can prevent relapse:
- **Awareness**: Recognize situations, people, or emotions that trigger cravings.
- **Planning**: Develop strategies for avoiding or coping with triggers.
- **Support**: Seek support from friends, family, or support groups when faced with triggers.
### Relapse Prevention
#### Understanding Relapse as Part of Recovery
Relapse is a common part of the recovery process:
- **Learning Opportunity**: Use relapse as an opportunity to learn and strengthen your recovery plan.
- **Not a Failure**: Recognize that relapse does not mean failure but requires renewed effort and support.
#### Identifying Triggers and Warning Signs
Being aware of triggers and warning signs can prevent relapse:
- **Emotional Triggers**: Stress, anxiety, and depression can trigger cravings.
- **Environmental Triggers**: Certain places, people, or situations can prompt relapse.
- **Behavioral Signs**: Changes in behavior, such as isolating or neglecting responsibilities, can signal a potential relapse.
#### Developing Coping Strategies
Effective coping strategies can help manage cravings and stress:
- **Distraction**: Engage in activities that divert your attention from cravings.
- **Mindfulness**: Practice mindfulness techniques to stay present and manage stress.
- **Support**: Reach out to your support network when feeling vulnerable.
#### Building Resilience and Emotional Strength
Building resilience is key to long-term recovery:
- **Self-Care**: Prioritize self-care activities that nurture your physical and mental health.
- **Positive Thinking**: Cultivate a positive mindset and focus on your progress and strengths.
- **Emotional Awareness**: Develop emotional awareness and learn to manage emotions effectively.
### Long-Term Recovery
#### Maintaining Motivation and Commitment
Sustaining motivation is crucial for long-term recovery:
- **Set Goals**: Regularly set and review short-term and long-term goals.
- **Celebrate Successes**: Acknowledge and celebrate milestones and achievements.
- **Stay Connected**: Maintain connections with your support network and continue attending support groups.
#### Continuing Therapy and Support
Ongoing therapy and support are essential for sustained recovery:
- **Regular Sessions**: Continue attending therapy sessions to address ongoing challenges.
- **Support Groups**: Stay involved in support groups for continued encouragement and accountability.
- **Aftercare Programs**: Participate in aftercare programs that provide ongoing support and resources.
#### Setting Long-Term Goals and Celebrating Milestones
Setting goals and celebrating milestones can motivate
you to stay on track:
- **Personal Goals**: Set personal goals related to health, relationships, and career.
- **Recovery Milestones**: Celebrate milestones such as sobriety anniversaries.
- **Recognition**: Acknowledge your progress and reward yourself for your achievements.
#### Giving Back: Helping Others in Their Recovery Journey
Helping others can reinforce your own recovery:
- **Volunteering**: Volunteer in organizations that support addiction recovery.
- **Mentorship**: Become a mentor or sponsor to others in recovery.
- **Advocacy**: Advocate for addiction awareness and support in your community.
### Personal Stories and Testimonials
#### Success Stories of Overcoming Addiction
Hearing success stories can inspire and motivate:
- **Real-Life Examples**: Share real-life stories of individuals who have successfully overcome addiction.
- **Lessons Learned**: Highlight the lessons learned and strategies that worked for them.
- **Inspiration**: Provide inspiration and hope for those currently struggling.
#### Learning from Others’ Experiences
Learning from others’ experiences can provide valuable insights:
- **Challenges and Triumphs**: Understand the challenges faced and triumphs achieved by others.
- **Practical Advice**: Gain practical advice and tips from those who have been through the recovery process.
- **Support and Encouragement**: Feel supported and encouraged by knowing you are not alone.
#### The Power of Sharing Your Story
Sharing your story can be a powerful part of your recovery:
- **Healing**: Sharing your story can be a therapeutic and healing experience.
- **Connection**: Connect with others who have similar experiences and build a support network.
- **Inspiration**: Inspire and motivate others by sharing your journey and successes.
### Resources and Further Reading
#### Books and Articles on Addiction and Recovery
Recommended reading for further information and support:
- **Books**: List of books that provide insights, strategies, and support for addiction recovery.
- **Articles**: Articles that offer practical advice and research on addiction and recovery.
- **Research Studies**: Summaries of key research studies on addiction and treatment.
#### Online Resources and Support Groups
Online resources for additional support and information:
- **Websites**: List of reputable websites that offer information and support for addiction recovery.
- **Online Forums**: Online forums and communities where individuals can share experiences and support each other.
- **Support Groups**: Online support groups that provide a virtual community for those in recovery.
#### Contact Information for Support Services and Hotlines
Important contact information for immediate support:
- **Hotlines**: List of hotlines for immediate help and support.
- **Support Services**: Contact information for local and national support services.
- **Treatment Centers**: Information on finding and contacting treatment centers.
### Conclusion
#### Recap of Key Points
Summarize the key points covered in the guide:
- **Understanding Addiction**: The science and psychology behind addiction.
- **Recognizing the Problem**: How to identify addiction in yourself and others.
- **Seeking Help**: Treatment options and how to find support.
- **Long-Term Recovery**: Strategies for maintaining recovery and preventing relapse.
#### Encouragement and Final Words of Support
Offer encouragement and support to those on the recovery journey:
- **Stay Positive**: Emphasize the importance of maintaining a positive attitude and perseverance.
- **You Are Not Alone**: Remind individuals that they are not alone and that support is available.
- **Continued Journey**: Acknowledge that recovery is an ongoing journey and encourage individuals to stay committed.
#### The Ongoing Journey of Recovery
Recovery is a lifelong journey that requires ongoing effort and support:
- **Commitment**: Stay committed to your recovery goals and continue working towards a healthier, fulfilling life.
- **Support**: Rely on your support network and seek help when needed.
- **Hope**: Maintain hope and believe in your ability to overcome addiction and achieve long-term recovery.
---
This outline provides a comprehensive framework for a 10,000-word guide on overcoming addiction. Each section would be expanded with detailed information, practical advice, and supportive resources to create a thorough and helpful guide for individuals seeking to overcome addiction.
### What Does NeoLife Mean? Let's Chat About It!
Hey there! Have you ever wondered what NeoLife really means? It's more than just a catchy name—there's a lot of thought and intention behind it. So, let’s dive into the story and meaning of NeoLife in a fun and conversational way.
#### The Name: NeoLife
First off, let’s break down the name itself. “Neo” comes from the Greek word for “new.” So, when you hear “NeoLife,” you’re really hearing “New Life.” It’s all about starting fresh, embracing vitality, and transforming your health and well-being. Sounds inspiring, right?
#### The Vision Behind NeoLife
Now, imagine you're Jerry Brassfield, the founder of NeoLife. You're passionate about nutrition because you’ve seen firsthand how it can change lives—starting with your own. Jerry struggled with severe asthma and allergies as a kid, and it was proper nutrition that helped him find relief. This personal experience sparked a lifelong mission to help others live healthier, more vibrant lives.
#### A Focus on Nutrition
So, what does NeoLife focus on? It’s all about harnessing the power of nutrition. The company creates supplements and health products designed to fill in the nutritional gaps in our diets. Think about it: even if you eat your veggies and fruits, it’s tough to get all the nutrients your body needs. That’s where NeoLife steps in, offering products that are scientifically formulated to support overall health.
#### Quality and Science
NeoLife isn’t just throwing ingredients into a bottle and calling it a day. They’ve got a team of top-notch scientists and nutrition experts working to ensure everything is backed by solid research. This means you’re getting products that are not only effective but also safe and natural. It’s like having a team of nutritionists in your corner, making sure you’re getting the best of the best.
#### The NeoLife Community
But wait, there’s more! NeoLife isn’t just about selling products—it’s about building a community. When you join NeoLife, whether as a customer or a distributor, you’re joining a global family dedicated to health and wellness. It’s about sharing knowledge, supporting each other, and making a positive impact together.
#### Empowerment Through Opportunity
Here’s another cool aspect: NeoLife offers a business opportunity for those who want to take it a step further. As a distributor, you can build your own business by sharing NeoLife products with others. It’s about empowering people to take control of their health and their financial future. So, not only can you improve your well-being, but you can also help others do the same while earning an income.
# Giving Back
NeoLife also believes in giving back. Through the NeoLife Foundation, the company supports various charitable initiatives, focusing on health, education, and community development. It’s all about making a difference in the world, one step at a time.
### Wrapping It Up
So, what does NeoLife mean? It’s a commitment to a new life filled with health, vitality, and opportunity. It’s about quality nutrition, scientific integrity, and building a supportive community. Whether you’re looking to improve your own health or help others do the same, NeoLife offers the tools and the platform to make it happen.
Next time you hear “NeoLife,” remember it’s more than a name—it’s a movement towards a better, healthier life for everyone. And who wouldn’t want to be a part of that?
### How NeoLife Pays Its Distributors in Nigeria
NeoLife, a global health and wellness company, has established a strong presence in Nigeria, offering individuals an opportunity to improve their health and financial well-being. The company's compensation plan is designed to reward distributors for their efforts in selling products and building a team. Let's delve into how NeoLife pays its distributors in Nigeria and the various income streams available.
#### 1. **Retail Profit**The most straightforward way to earn with NeoLife in Nigeria is through retail profit. Distributors purchase products at wholesale prices and sell them at retail prices. The difference between these two prices is the distributor's profit. This immediate income source is crucial for those who are actively engaged in direct selling to customers.
#### 2. **Personal Sales Bonus**
Distributors earn a Personal Sales Bonus based on their monthly personal sales volume. This bonus rewards distributors for their direct selling efforts, providing an additional income stream beyond retail profit. The more products a distributor sells, the higher the bonus they receive.
#### 3. **Team Building Bonus**
NeoLife's compensation plan encourages team building. Distributors earn a Team Building Bonus by recruiting new distributors and helping them succeed. This bonus is calculated based on the sales volume generated by the new recruits, known as the downline. In Nigeria, where community and networks are vital, this aspect of the compensation plan can be particularly effective.
#### 4. **Leadership Development Bonus**
For those who excel in developing leaders within their team, the Leadership Development Bonus is an attractive feature. Distributors who help their downline members advance to higher ranks earn this bonus. It incentivizes mentorship and leadership, ensuring that experienced distributors support and guide new recruits to success.
#### 5. **Director and Above Bonuses**
Reaching the rank of Director and beyond opens up significant earning opportunities. Directors and higher-ranked distributors in Nigeria receive additional bonuses based on their overall team performance and total sales volume. These bonuses reflect the distributor's leadership and the success of their entire team.
#### 6. **Lifestyle Bonuses and Incentives**
NeoLife offers various lifestyle bonuses and incentives to its Nigerian distributors. These incentives can include trips, cars, and other rewards for meeting specific sales and recruitment targets. Such incentives motivate distributors to aim higher and achieve their goals, adding excitement and recognition to their efforts.
#### 7. **Residual Income**
One of the most compelling aspects of NeoLife's compensation plan is the potential for residual income. As distributors build a robust customer base and a successful team, they continue to earn commissions on sales made by their downline. This ongoing income provides long-term financial stability, rewarding distributors for their hard work and dedication over time.
### Special Considerations for Nigeria
In Nigeria, the economic environment and cultural factors play a significant role in how NeoLife's compensation plan is perceived and utilized. Here are some unique aspects to consider:
- **Community Networks:** Nigerian distributors often leverage their strong community networks to build their business. This makes the Team Building and Leadership Development Bonuses particularly effective.
- **Entrepreneurial Spirit:** There is a growing entrepreneurial spirit in Nigeria, with many individuals looking for opportunities to start their own business. NeoLife's compensation plan offers a viable pathway for those seeking financial independence.
- **Training and Support:** NeoLife provides training and support tailored to the Nigerian market, ensuring that distributors have the knowledge and tools they need to succeed.
### Conclusion
NeoLife's compensation plan in Nigeria is designed to be lucrative and motivational, offering multiple income streams and substantial bonuses for dedicated distributors. By focusing on both direct sales and team development, NeoLife empowers individuals to build a sustainable and profitable business. Whether you're looking to earn extra income or build a full-time career, NeoLife in Nigeria provides a comprehensive and rewarding business opportunity.
### How to Log In to the NeoLife Website: A Step-
by-Step Guide
Logging in to the NeoLife website is an essential step for distributors and customers who want to access their accounts, manage their orders, view their earnings, and utilize the various tools and resources available. Whether you're new to NeoLife or just need a refresher, this step-by-step guide will help you navigate the login process with ease.
#### Step 1: Visit the NeoLife Website
Open your preferred web browser and go to the official NeoLife website. The URL is usually [www.neolife.com](http://www.neolife.com). Make sure you are on the correct regional site if NeoLife operates different portals for different countries.
#### Step 2: Locate the Login Button
Once you are on the homepage, look for the "Login" button. This is typically found in the upper right-hand corner of the page. It might be labeled as "Distributor Login" or "Member Login," depending on your region.
#### Step 3: Enter Your Login Credentials
Clicking on the "Login" button will take you to the login page, where you will need to enter your credentials:
- **Username or Email:** Enter the username or email address associated with your NeoLife account.
- **Password:** Enter your password. Make sure it is typed correctly, paying attention to capitalization and any special characters.
#### Step 4: Click "Log In"
After entering your username and password, click the "Log In" button. If your credentials are correct, you will be redirected to your account dashboard.
#### Step 5: Navigating Your Account Dashboard
Once logged in, you will have access to various features and tools depending on your role (distributor or customer). Here are some common areas you might find:
- **Order Management:** View and manage your orders, track shipments, and reorder products.
- **Earnings and Bonuses:** Check your earnings, bonuses, and commission statements.
- **Training and Resources:** Access training materials, product information, and marketing tools.
- **Personal Information:** Update your personal details, contact information, and account settings.
- **Support:** Get help and support from NeoLife customer service.
#### Forgot Your Password?
If you forget your password, don’t worry. On the login page, there is usually a "Forgot Password?" link. Click on it and follow these steps:
1. **Enter Your Email:** Provide the email address associated with your NeoLife account.
2. **Check Your Email:** NeoLife will send a password reset link to your email. Open this email and click on the link.
3. **Reset Your Password:** Follow the instructions to create a new password. Make sure it is strong and secure.
4. **Log In:** Use your new password to log in to your account.
#### Tips for a Smooth Login Experience
- **Bookmark the Login Page:** Save the NeoLife login page in your browser bookmarks for easy access.
- **Use a Secure Password:** Ensure your password is strong and not easily guessable. Use a mix of letters, numbers, and special characters.
- **Keep Your Credentials Safe:** Never share your login details with others and avoid using public computers to access your account.
- **Enable Two-Factor Authentication:** If NeoLife offers two-factor authentication, enable it for an extra layer of security.
### Conclusion
Logging in to the NeoLife website is a straightforward process that gives you access to a wealth of resources and tools to manage your health and business activities. By following these simple steps, you can easily access your account and make the most of what NeoLife has to offer. Whether you're placing orders, checking your earnings, or exploring training materials, the NeoLife website is designed to support your journey towards better health and financial success.
### Discover the Power of NeoLife Supplements: Your Path to
Better Health
In today's fast-paced world, maintaining optimal health can be a challenge. Our diets often lack essential nutrients, and busy lifestyles can leave us feeling tired and run down. That's where NeoLife supplements come in. With a commitment to quality and scientifically-backed formulations, NeoLife offers a range of products designed to support your overall well-being. Let's explore what makes NeoLife supplements stand out and how they can help you achieve better health.
#### The NeoLife Difference
NeoLife has been a trusted name in the health and wellness industry for over 60 years. Founded by Jerry Brassfield, who experienced the transformative power of nutrition firsthand, the company has a clear mission: to make the world a healthier and happier place by providing the finest nutritional products.
#### Scientifically Backed Formulations
One of the key factors that set NeoLife supplements apart is their commitment to science. The company boasts a Scientific Advisory Board composed of leading scientists and nutrition experts who ensure that all products are based on the latest research and adhere to the highest standards of quality and efficacy.
NeoLife’s products are designed to bridge the gap between what we eat and what our bodies need. Even with the best intentions, it's challenging to get all the essential nutrients from food alone. NeoLife supplements provide a convenient way to ensure you're getting the vitamins, minerals, and other nutrients necessary for optimal health.
#### Whole-Food-Based Ingredients
NeoLife prides itself on using whole-food-based ingredients in its supplements. This means that the nutrients come from natural sources like fruits, vegetables, and whole grains, rather than synthetic alternatives. The company believes in the power of nature to provide the best nutrition, and this philosophy is reflected in their product formulations.
For instance, NeoLife’s flagship product, **Pro Vitality**, includes a blend of essential nutrients derived from whole foods. It contains four key components: a multivitamin, omega-3 fatty acids, antioxidant protection, and a nutrient booster. This comprehensive approach ensures that your body gets a balanced array of nutrients to support overall health.
#### A Range of Products for Different Needs
NeoLife offers a variety of supplements tailored to meet different health needs. Here are a few examples:
- **Vita-Squares**: Chewable multivitamins for children, providing essential nutrients for growth and development.
- **Tre-en-en**: A unique supplement that supports cellular health and energy by providing essential lipids and sterols.
- **Omega-3 Salmon Oil Plus**: High-quality omega-3 fatty acids from pure salmon oil, supporting heart health, brain function, and joint health.
- **NeoLifeShake**: A protein-rich meal replacement shake that helps with weight management and provides sustained energy.
#### Quality You Can Trust
Quality control is a top priority for NeoLife. The company follows strict manufacturing practices to ensure that every product meets the highest standards of purity, potency, and safety. This commitment to quality is why so many people around the world trust NeoLife supplements to support their health.
#### Testimonials from Real People
Countless individuals have experienced the benefits of NeoLife supplements. From increased energy levels and improved digestion to better immune function and overall vitality, the positive feedback speaks volumes about the effectiveness of these products.
For example, Jane, a busy mother of three, shares her experience: "NeoLife supplements have been a game-changer for me. With Pro Vitality and NeoLifeShake, I feel more energized and balanced throughout the day. It’s reassuring to know I’m giving my body the nutrients it needs."
### Conclusion
NeoLife supplements offer a practical and effective solution for anyone looking to enhance their health and well-being. With a foundation in scientific research, whole-food-based ingredients, and a commitment to quality, NeoLife stands out in the crowded supplement market. Whether you’re seeking to boost your energy, support your immune system, or improve your overall nutrition, NeoLife has a product to help you on your journey to better health.
So why not give NeoLife supplements a try? Your body will thank you for it!
### Jerry Brassfield: The Visionary Behind NeoLife
Jerry Brassfield is a name synonymous with innovation and dedication in the health and wellness industry. As the founder of NeoLife, a global company that has transformed countless lives through superior nutrition products, Brassfield's journey is one of resilience, vision, and unwavering commitment to better health.
#### Early Life and Inspiration
Jerry Brassfield was born in the small town of Oroville, California, in 1940. His early life was marked by severe health challenges, including debilitating asthma and allergies. Traditional treatments offered little relief, leading his mother to explore nutritional solutions. This personal experience with the healing power of nutrition ignited Brassfield's passion for health and wellness, setting the stage for his future endeavors.
#### The Birth of NeoLife
In 1958, at just 19 years old, Jerry Brassfield founded NeoLife, initially known as Golden Products. His mission was clear: to provide high-quality nutritional supplements that could help others achieve optimal health, just as they had for him. Brassfield's approach was revolutionary for its time. He combined the principles of nature with cutting-edge scientific research to develop products that were both effective and safe.
#### Commitment to Quality and Science
Under Brassfield's leadership, NeoLife has always prioritized quality and scientific integrity. The company established a Scientific Advisory Board comprising leading scientists and nutrition experts to ensure that all products are backed by rigorous research and adhere to the highest standards of quality. This commitment to excellence has earned NeoLife a reputation for producing some of the most trusted and effective nutritional supplements on the market.
#### Building a Global Network
Jerry Brassfield's vision extended beyond creating exceptional products. He wanted to empower people to build their own businesses and improve their lives. Through NeoLife's multi-level marketing (MLM) model, individuals have the opportunity to become distributors, sharing the benefits of NeoLife products while earning an income. This business model has helped NeoLife grow into a global network, spanning over 50 countries and impacting countless lives positively.
#### Philanthropy and Giving Back
Success has not dulled Jerry Brassfield's commitment to giving back. He is actively involved in various philanthropic endeavors, focusing on health, education, and community development. The NeoLife Foundation, established by Brassfield, supports numerous charitable initiatives, including nutritional support for underserved communities and funding for educational programs. This philanthropic spirit reflects Brassfield's belief in the power of giving and the importance of helping others.
#### Personal Values and Leadership Style
Jerry Brassfield is known for his hands-on leadership style and his unwavering commitment to integrity and excellence. He believes in leading by example, and his personal values are deeply ingrained in NeoLife's corporate culture. Brassfield's emphasis on family, health, and personal development resonates throughout the organization, fostering a supportive and inspiring environment for distributors and employees alike.
#### Legacy and Future Vision
As NeoLife continues to grow and evolve, Jerry Brassfield remains at the helm, guiding the company with his visionary leadership. His legacy is not just in the products NeoLife offers but in the lives it transforms through improved health and the opportunity for financial independence. Brassfield's dedication to innovation and his relentless pursuit of excellence ensure that NeoLife will continue to be a leader in the health and wellness industry for years to come.
### Conclusion
Jerry Brassfield's journey from a young boy struggling with health issues to the founder of a global health and wellness company is a remarkable story of vision, perseverance, and passion. Through NeoLife, Brassfield has not only provided superior nutritional products but has also empowered thousands of individuals to achieve better health and financial freedom. His enduring commitment to quality, science, and helping others serves as an inspiration and a testament to what can be achieved with dedication and a clear vision. Jerry Brassfield is more than just a successful entrepreneur; he is a pioneer in the quest for better health for all.
## Managing Cholesterol #with NeoLife Supplements: A Path to Heart Health
High cholesterol is a common health issue that can lead to serious cardiovascular problems if left unmanaged. With the rise of lifestyle-related diseases, it's essential to find effective ways to maintain healthy cholesterol levels. NeoLife, a global leader in health and wellness, offers a range of supplements specifically designed to support heart health and manage cholesterol. Let's explore how NeoLife supplements can help you maintain a healthy heart and manage your cholesterol levels effectively.
#### Understanding Cholesterol
Cholesterol is a fatty substance found in your blood, essential for building healthy cells. However, having high levels of low-density lipoprotein (LDL) cholesterol, often referred to as "bad" cholesterol, can lead to plaque buildup in your arteries, increasing the risk of heart disease and stroke. Conversely, high-density lipoprotein (HDL) cholesterol, or "good" cholesterol, helps remove LDL cholesterol from your bloodstream.
#### NeoLife Supplements for Cholesterol Management
NeoLife offers several supplements formulated to support healthy cholesterol levels and promote overall heart health. These products are backed by scientific research and contain high-quality, whole-food-based ingredients. Here are some of the key supplements:
1. **Omega-3 Salmon Oil Plus**
Omega-3 fatty acids are well-known for their heart health benefits. NeoLife's Omega-3 Salmon Oil Plus is a high-quality supplement that provides a full spectrum of omega-3s, including EPA and DHA. These essential fatty acids help reduce triglycerides, lower blood pressure, and increase HDL cholesterol levels, thereby supporting overall cardiovascular health.
- **Benefits**:
- Reduces inflammation
- Lowers LDL cholesterol and triglycerides
- Increases HDL cholesterol
- Supports heart and brain health
2. **Lipotropic Adjunct**
NeoLife's Lipotropic Adjunct is formulated to support healthy lipid metabolism. This supplement contains essential nutrients like choline, inositol, and methionine, which help break down fats in the liver and prevent the accumulation of excess fat, thereby promoting healthy cholesterol levels.
- **Benefits**:
- Supports liver function and fat metabolism
- Reduces LDL cholesterol
- Promotes the removal of fat from the liver
3. **Garlic Allium Complex**
Garlic has been used for centuries for its health benefits, particularly for heart health. NeoLife’s Garlic Allium Complex harnesses the power of garlic and other allium vegetables to support healthy cholesterol levels. Garlic has been shown to lower LDL cholesterol and increase HDL cholesterol, making it a valuable addition to a cholesterol management regimen.
- **Benefits**:
- Lowers LDL cholesterol
- Increases HDL cholesterol
- Provides antioxidant support
- Supports overall cardiovascular health
4. **Pro Vitality**
Pro Vitality is a comprehensive supplement that includes essential nutrients to support overall health and vitality. It contains Tre-en-en Grain Concentrates, Carotenoid Complex, Omega-3 Salmon Oil Plus, and Essential Vitamin & Mineral Complex. Together, these components help improve heart health, support healthy cholesterol levels, and provide broad-spectrum nutritional support.
- **Benefits**:
- Supports heart and brain health
- Provides essential vitamins and minerals
- Enhances overall vitality and energy levels
- Promotes healthy cholesterol levels
#### Incorporating NeoLife Supplements into Your Routine
For optimal results, it’s important to incorporate these supplements into a balanced diet and healthy lifestyle. Here are some tips:
- **Balanced Diet**: Eat a diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats. Limit your intake of saturated fats, trans fats, and cholesterol-rich foods.
- **Regular Exercise**: Engage in at least 30 minutes of moderate exercise most days of the week. Physical activity helps raise HDL cholesterol and lower LDL cholesterol.
- **Avoid Smoking and Limit Alcohol**: Smoking lowers HDL cholesterol, while excessive alcohol can raise your cholesterol levels.
- **Monitor Your Levels**: Regularly check your cholesterol levels to track your progress and make adjustments as needed.
### Conclusion
NeoLife supplements offer a natural and effective way to manage cholesterol levels and support heart health. With products like Omega-3 Salmon Oil Plus, Lipotropic Adjunct, Garlic Allium Complex, and Pro Vitality, you can take proactive steps toward maintaining healthy cholesterol levels and reducing your risk of cardiovascular disease. By combining these supplements with a healthy diet and lifestyle, you can pave the way to a healthier heart and a better quality of life.
### Supporting Joint Health with NeoLife
Supplements
Maintaining healthy joints is essential for overall mobility and quality of life, especially as we age. NeoLife, a renowned leader in health and wellness, offers a range of supplements specifically designed to support joint health and alleviate symptoms associated with joint conditions like arthritis. Whether you're looking to prevent joint issues or manage existing discomfort, NeoLife supplements can be a valuable addition to your daily routine.
#### The Challenge of Joint Health
As we grow older or due to various factors like genetics, injury, or lifestyle, our joints can undergo wear and tear. This wear and tear can lead to conditions like osteoarthritis, where the protective cartilage that cushions the ends of bones wears down over time. Rheumatoid arthritis, an autoimmune disorder, causes inflammation in the joints, leading to pain, stiffness, and reduced flexibility.
#### NeoLife's Approach to Joint Health
NeoLife understands the complexity of joint health and has developed supplements that address different aspects of joint care, from supporting cartilage and connective tissue to reducing inflammation and promoting overall joint function. Here are some key supplements that can benefit joint health:
1. NeoLife Salmon Oil Plus
Omega-3 fatty acids, found abundantly in fish oil like NeoLife Salmon Oil Plus, are known for their anti-inflammatory properties. These essential fatty acids help reduce inflammation in joints affected by arthritis, easing pain and improving joint function. Additionally, omega-3s support overall cardiovascular health, benefiting circulation and joint mobility.
2. NeoLife Chelated Cal-Mag with 1000 IU Vitamin D
Calcium, magnesium, and vitamin D are crucial for maintaining strong bones and supporting joint health. NeoLife’s Chelated Cal-Mag with Vitamin D provides these essential nutrients in a highly bioavailable form, ensuring optimal absorption. Adequate calcium and magnesium intake helps support bone density and may reduce the risk of osteoporosis, a condition common in those with arthritis.
3. **NeoLife Full Motion**
This supplement is specifically formulated to promote joint flexibility and mobility. NeoLife Full Motion contains glucosamine, chondroitin, and MSM (Methylsulfonylmethane), which are key ingredients known to support joint structure and function. Glucosamine and chondroitin help rebuild cartilage and improve joint cushioning, while MSM supports joint tissue elasticity and flexibility.
4. **NeoLife Tre-en-en Grain Concentrates**
Cellular health is crucial for maintaining joint integrity and function. NeoLife Tre-en-en Grain Concentrates provide essential lipids and sterols to support cell membrane function and overall cellular health. Healthy cells contribute to better joint lubrication and resilience against oxidative stress, which can exacerbate arthritis symptoms.
#### Incorporating NeoLife Supplements into Your Routine
To maximize the benefits of NeoLife supplements for joint health, consider the following tips:
- **Consistency**: Take supplements regularly as directed to maintain consistent support for joint health.
- **Healthy Diet**: Eat a balanced diet rich in fruits, vegetables, lean proteins, and whole grains to support overall health and supplement efficacy.
- **Physical Activity**: Engage in low-impact exercises like swimming, walking, or yoga to promote joint flexibility and mobility.
- **Consultation**: Consult with your healthcare provider before starting any new supplement regimen, especially if you have existing health conditions or are taking medications.
#### Conclusion
NeoLife supplements offer a proactive approach to supporting joint health and managing arthritis symptoms effectively. By incorporating products like NeoLife Salmon Oil Plus, Chelated Cal-Mag with Vitamin D, Full Motion, and Tre-en-en Grain Concentrates into your daily routine, you can enhance joint flexibility, reduce inflammation, and support overall joint function. With NeoLife's commitment to quality and scientific integrity, you can trust that you're giving your joints the best possible care for a healthier, more active lifestyle.
### Can Supplements Help with Arthritis? Exploring NeoLife's Approach
Arthritis, a condition characterized by inflammation and stiffness in the joints, affects millions of people worldwide, leading to pain and reduced mobility. While medical treatments and lifestyle changes are commonly prescribed, many individuals turn to supplements as a complementary approach to manage symptoms and support joint health. NeoLife, a prominent name in nutritional supplements, offers a range of products designed to aid in arthritis management. Let's delve into the potential benefits of supplements and NeoLife's approach to supporting those with arthritis.
#### Understanding Arthritis and Its Challenges
Arthritis encompasses various conditions that affect joints and surrounding tissues. The two most common types are osteoarthritis (OA) and rheumatoid arthritis (RA). OA occurs due to wear and tear on joints over time, while RA is an autoimmune disorder that causes inflammation in the joints. Both types can lead to pain, swelling, stiffness, and reduced range of motion, impacting daily life and overall well-being.
#### The Role of Supplements in Arthritis Management
Supplements are often sought after as a natural approach to alleviate arthritis symptoms and support joint health. While they are not a substitute for medical treatment prescribed by healthcare professionals, certain supplements have shown promise in clinical studies:
1. **Omega-3 Fatty Acids**: Found in fish oil supplements like NeoLife Salmon Oil Plus, omega-3 fatty acids have anti-inflammatory properties. They can help reduce inflammation in joints affected by arthritis, potentially easing pain and improving joint function.
2. **Glucosamine and Chondroitin**: These are natural compounds found in healthy cartilage. They are commonly used together in supplements like NeoLife Full Motion to support joint structure and function. Glucosamine helps build and repair cartilage, while chondroitin helps keep it hydrated and elastic.
3. **Vitamin D**: Essential for bone health, vitamin D plays a role in calcium absorption and maintaining bone density. NeoLife’s Chelated Cal-Mag with Vitamin D provides this crucial nutrient, supporting overall bone and joint health.
4. **Turmeric/Curcumin**: Known for its anti-inflammatory properties, turmeric (curcumin) supplements may help reduce joint pain and stiffness in arthritis. NeoLife's products may contain turmeric as part of their formulas aimed at joint health.
#### NeoLife's Approach to Supporting Joint Health
NeoLife supplements are formulated with high-quality, whole-food-based ingredients and backed by scientific research. Here's how NeoLife addresses joint health:
- **Comprehensive Formulations**: Products like NeoLife Full Motion combine glucosamine, chondroitin, MSM (Methylsulfonylmethane), and other nutrients to support joint flexibility, mobility, and comfort.
- **Scientific Advisory Board**: NeoLife’s commitment to scientific integrity ensures that all products undergo rigorous testing and quality control to meet the highest standards.
- **Personalized Support**: Distributors and customers have access to personalized guidance and education on product usage and benefits, enhancing the effectiveness of supplement regimens.
#### Incorporating Supplements into Your Arthritis Management Plan
While supplements can be beneficial, it's essential to use them as part of a comprehensive arthritis management plan. Here are some tips:
- **Consult with Your Healthcare Provider**: Before starting any new supplement regimen, consult with your doctor or rheumatologist, especially if you're on medications or have existing health conditions.
- **Follow Dosage Instructions**: Take supplements as directed to ensure maximum effectiveness and safety.
- **Combine with Healthy Habits**: Maintain a balanced diet, engage in regular exercise (appropriate for your condition), manage stress levels, and maintain a healthy weight—all of which can positively impact arthritis symptoms.
#### Conclusion
Supplements like those offered by NeoLife can play a supportive role in managing arthritis symptoms and promoting joint health. By incorporating scientifically-backed products into your daily routine, alongside medical advice and healthy lifestyle choices, you can take proactive steps toward managing arthritis and improving your overall quality of life. Always prioritize personalized healthcare guidance to tailor your supplement regimen to your specific needs and condition.
### Exploring the NeoLife Distributor Website: Your Gateway to Health and Success
Becoming a NeoLife distributor is more than just a business opportunity; it's a chance to join a global community dedicated to improving health and empowering individuals. The NeoLife distributor website is a comprehensive platform designed to support distributors in their journey, providing essential tools, resources, and information. In this article, we’ll explore the key features of the NeoLife distributor website and how it can help you succeed.
#### Getting Started with NeoLife
When you sign up as a NeoLife distributor, you gain access to a wealth of resources through the distributor website. Here’s what you can expect when you first log in:
1. **User-Friendly Dashboard**
The NeoLife distributor website features an intuitive dashboard that provides a snapshot of your business. Here, you can track your sales, monitor your team’s performance, and stay updated on the latest news and promotions. The dashboard is designed to help you stay organized and focused on your goals.
2. **Product Information and Training**
Understanding the products you’re selling is crucial for success. The distributor website offers detailed information on all NeoLife products, including ingredients, benefits, and usage instructions. Additionally, you’ll find training materials such as videos, webinars, and articles that can help you become more knowledgeable and confident in promoting NeoLife products.
3. **Business Tools and Resources**
The distributor website is equipped with a variety of tools to help you manage and grow your business. These include:
- **Sales Reports**: Track your sales performance and identify trends to optimize your strategy.
- **Marketing Materials**: Access brochures, flyers, and social media assets to effectively promote NeoLife products and business opportunities.
- **Order Management**: Easily place orders for your customers and manage your inventory.
4. **Training and Development**
Continuous learning is key to staying ahead in any business. NeoLife provides ongoing training and development resources through the distributor website. Participate in live webinars, watch recorded training sessions, and read articles from industry experts to enhance your skills and knowledge.
5. **Community and Support**
As a NeoLife distributor, you’re part of a global community. The distributor website offers forums and social media groups where you can connect with other distributors, share experiences, and seek advice. Additionally, you have access to customer support for any questions or issues you might encounter.
#### The Benefits of Being a NeoLife Distributor
Joining NeoLife as a distributor offers numerous benefits, including:
- **Financial Opportunity**: Earn commissions on sales and build a residual income through team building.
- **Flexibility**: Work on your own terms and schedule, making it an ideal opportunity for those seeking work-life balance.
- **Personal Growth**: Develop valuable skills in sales, marketing, and leadership while making a positive impact on others’ health and well-being.
- **Exclusive Discounts**: Enjoy discounts on NeoLife products for personal use or resale.
#### Steps to Success as a NeoLife Distributor
To maximize your success as a NeoLife distributor, consider the following steps:
1. **Set Clear Goals**: Define your business objectives and create a plan to achieve them.
2. **Leverage Training Resources**: Take advantage of the training materials and support available on the distributor website.
3. **Network and Build Relationships**: Connect with potential customers and fellow distributors to expand your network.
4. **Promote Consistently**: Use the marketing materials provided to promote NeoLife products and business opportunities regularly.
5. **Stay Informed**: Keep up with the latest product updates, promotions, and business strategies through the distributor website.
#### Conclusion
The NeoLife distributor website is a powerful tool designed to help you succeed in your journey as a distributor. From product information and training to business tools and community support, the website provides everything you need to build and grow your NeoLife business. By leveraging these resources and staying committed to your goals, you can achieve success and make a positive impact on the health and lives of others. Join the NeoLife family today and start your journey towards a healthier, more prosperous future.
### Unlocking Vitality with NeoLife Tre-en-en: The Power of Cellular Nutrition
In our quest for better health and vitality, ensuring our cells function optimally is key. NeoLife Tre-en-en is a revolutionary supplement that focuses on cellular nutrition, providing essential lipids and sterols to support cellular membrane health and overall vitality. Let's explore what makes Tre-en-en unique and how it can benefit your health.
#### What is NeoLife Tre-en-en?
NeoLife Tre-en-en is a proprietary blend of essential lipids and sterols derived from cold-pressed oils of wheat germ, rice bran, and soybeans. These oils are carefully processed to preserve their nutritional integrity and ensure maximum bioavailability. Tre-en-en works by replenishing important lipids and sterols that are vital for cell membrane structure and function.
#### The Importance of Cellular Nutrition
Cell membranes play a crucial role in cellular health and function. They act as gatekeepers, regulating the flow of nutrients into cells and waste products out of cells. Healthy cell membranes are essential for optimal cellular communication, energy production, and overall well-being. However, modern diets often lack sufficient amounts of essential lipids and sterols, which can impact cellular health over time.
#### Benefits of NeoLife Tre-en-en
1. **Supports Cellular Membrane Function**: Tre-en-en provides lipids and sterols that help maintain the integrity and fluidity of cell membranes. This supports efficient nutrient transport and waste removal, crucial for cellular health and function.
2. **Enhances Energy Production**: By supporting mitochondrial function, Tre-en-en helps optimize energy production within cells. This can lead to increased energy levels and overall vitality.
3. **Supports Cardiovascular Health**: Healthy cell membranes are essential for maintaining cardiovascular health. Tre-en-en's nutritional support can contribute to healthy blood flow and cardiovascular function.
4. **Promotes Skin Health**: Cell membranes also play a role in maintaining skin elasticity and hydration. Tre-en-en's lipid and sterol content supports healthy skin from within.
5. **Supports Immune Function**: Optimal cellular health is linked to a well-functioning immune system. By supporting cellular membranes, Tre-en-en helps support immune function and response.
#### Why Choose NeoLife Tre-en-en?
NeoLife Tre-en-en stands out due to its unique formulation and the quality of its ingredients:
- **Whole-Food Derived**: Derived from natural sources like wheat germ, rice bran, and soybeans, Tre-en-en provides nutrients in a form that your body recognizes and utilizes effectively.
- **Clinically Proven**: Backed by scientific research, Tre-en-en has been shown to enhance nutrient absorption, improve cellular function, and support overall vitality.
- **Trusted Brand**: NeoLife has been a leader in nutritional supplements for over 60 years, with a commitment to quality and scientific integrity. Tre-en-en reflects this commitment by delivering consistent results and benefits.
#### Incorporating Tre-en-en into Your Routine
To experience the benefits of Tre-en-en, incorporate it into your daily routine:
- **Recommended Dosage**: Follow the recommended dosage as directed on the product label or by your healthcare provider.
- **Consistency**: Consistent use is key to experiencing the full benefits of Tre-en-en. Incorporate it into your morning routine or with meals for best results.
- **Combine with a Balanced Diet**: While Tre-en-en provides essential nutrients, it should complement a balanced diet rich in fruits, vegetables, lean proteins, and whole grains.
#### Conclusion
NeoLife Tre-en-en offers a unique approach to supporting overall vitality and health by focusing on cellular nutrition. By providing essential lipids and sterols that support cellular membrane function, Tre-en-en helps optimize energy production, enhance nutrient absorption, and support overall well-being. Whether you're looking to boost your energy levels, support cardiovascular health, or enhance your overall vitality, Tre-en-en can be a valuable addition to your daily wellness regimen. Choose NeoLife Tre-en-en and unlock the power of cellular nutrition for a healthier, more vibrant life.
Understanding NeoLife Product Pricing
I can't provide a specific price list for NeoLife products as they can vary by region, distributor, and promotional offers. Instead, I can help you understand how NeoLife's pricing generally works and what factors might influence product costs.
### Understanding NeoLife Product Pricing
NeoLife is known for offering a range of nutritional supplements and wellness products designed to support various aspects of health. Here’s a general overview of factors that can influence NeoLife product pricing:
#### 1. Product Type and Formulation
NeoLife offers a diverse portfolio of products, including vitamins, minerals, dietary supplements, weight management products, and personal care items. The complexity and ingredients of each product can affect its pricing. For example, supplements with premium ingredients or specific formulations may be priced differently than more basic products.
#### 2. Size and Quantity
The size of the product and the quantity per package can impact pricing. Larger quantities or bundles may offer better value per unit compared to smaller packages. NeoLife often provides options for purchasing products individually or in bulk, which can affect overall pricing.
#### 3. Promotions and Discounts
NeoLife frequently runs promotions, discounts, and special offers for its products. These can include seasonal sales, bundle deals, loyalty rewards for distributors, and introductory offers for new customers. Taking advantage of these promotions can help customers and distributors save on their purchases.
#### 4. Geographic Region and Currency
Pricing may vary by geographic region and currency exchange rates. NeoLife operates in multiple countries worldwide, and product prices can be influenced by local market conditions, distribution costs, and regulatory requirements.
#### 5. Distributor Pricing
NeoLife operates on a direct selling or network marketing model, where distributors sell products directly to consumers. Distributors may offer products at different price points based on their individual business strategies, customer relationships, and the benefits they provide, such as personalized support and additional services.
#### How to Obtain Pricing Information
To obtain specific pricing information for NeoLife products:
- **Visit the NeoLife Website**: The official NeoLife website may provide general pricing guidelines or allow you to contact a distributor for more information.
- **Contact a NeoLife Distributor**: NeoLife distributors are knowledgeable about product pricing and can provide personalized advice based on your health goals and budget.
- **Attend NeoLife Events**: NeoLife often hosts events where attendees can learn more about products, pricing, and special offers directly from company representatives.
### Conclusion
While I can’t provide an exact price list due to variability, NeoLife offers a wide range of products designed to support health and wellness through quality nutrition. Understanding the factors influencing pricing can help you make informed decisions when purchasing NeoLife products. Whether you're looking to enhance your nutritional intake, manage weight, or support specific health goals, NeoLife products aim to provide effective solutions backed by decades of research and innovation. For the most accurate pricing and personalized recommendations, consider reaching out to a NeoLife distributor or visiting their official website.
### Nourish Your Hair with NeoLife: Supporting Natural Hair Growth
Achieving healthy, vibrant hair is a goal shared by many, and NeoLife offers a range of products designed to support and enhance hair growth naturally. Whether you're struggling with thinning hair, looking to boost volume, or simply aiming for stronger strands, NeoLife's scientifically-backed supplements can be a valuable addition to your hair care regimen. Let's explore how NeoLife products can help nourish your hair and promote optimal growth.
#### Understanding Hair Growth
Before delving into NeoLife's solutions, it's important to understand the basics of hair growth. Hair growth occurs in cycles with three main phases:
1. **Anagen Phase**: The active growth phase where hair cells divide rapidly, resulting in new hair growth.
2. **Catagen Phase**: A transitional phase where hair growth slows down, and the hair follicle shrinks.
3. **Telogen Phase**: The resting phase where old hair is released and falls out, making way for new hair growth.
The health of your hair follicles, scalp environment, and overall nutritional status can influence the duration and quality of each phase.
#### NeoLife Products for Hair Growth
NeoLife offers several products enriched with essential nutrients and botanical extracts that support healthy hair growth and maintenance:
1. **NeoLife Pro Vitality**
Pro Vitality is a comprehensive daily supplement pack that includes essential vitamins, minerals, and phytonutrients. These nutrients support overall health, including the health of your hair follicles and scalp. A balanced nutritional intake is essential for maintaining healthy hair growth cycles.
2. **NeoLife NutriShake**
NutriShake is a protein-rich meal replacement shake that provides essential amino acids, vitamins, and minerals. Protein is crucial for hair structure, as hair strands are primarily made of a protein called keratin. Ensuring an adequate protein intake supports strong and healthy hair growth.
3. **NeoLife Tré Nutritional Essence**
Tré Nutritional Essence is formulated with antioxidant-rich ingredients like aloe vera, green tea extract, and grape seed extract. These antioxidants help protect hair follicles from oxidative stress, which can contribute to hair damage and loss.
4. **NeoLife Salmon Oil Plus**
Omega-3 fatty acids found in fish oil, such as those in NeoLife Salmon Oil Plus, are essential for scalp health and hair follicle nourishment. Omega-3s support a healthy inflammatory response in the scalp and promote optimal conditions for hair growth.
#### How NeoLife Products Support Hair Health
- **Promoting Scalp Circulation**: Nutrients like vitamins A, C, E, and biotin found in NeoLife products support scalp circulation, ensuring that hair follicles receive adequate oxygen and nutrients for optimal growth.
- **Strengthening Hair Follicles**: Essential minerals such as zinc and selenium help strengthen hair follicles, reducing breakage and promoting thicker, stronger hair strands.
- **Enhancing Nutrient Absorption**: NeoLife products are designed for optimal nutrient absorption, ensuring that your body efficiently utilizes the vitamins, minerals, and antioxidants needed for healthy hair growth.
#### Incorporating NeoLife Products into Your Routine
To maximize the benefits of NeoLife products for hair growth:
- **Follow Recommended Dosages**: Take NeoLife supplements as directed to ensure consistent nutrient intake.
- **Maintain a Balanced Diet**: Incorporate a variety of nutrient-rich foods into your diet, including fruits, vegetables, lean proteins, and whole grains.
- **Practice Good Hair Care**: Use gentle hair care products suitable for your hair type and avoid excessive heat styling or chemical treatments that can damage hair.
#### Conclusion
NeoLife products offer a holistic approach to supporting healthy hair growth by providing essential nutrients, antioxidants, and omega-3 fatty acids that nourish hair follicles from within. Whether you're looking to address hair thinning, enhance volume, or maintain overall hair health, NeoLife's scientifically-formulated supplements can help you achieve stronger, more resilient hair. Embrace a comprehensive approach to hair care with NeoLife and nurture your hair for lasting vitality and beauty.
I'm sorry for any confusion, but it seems there might be a misunderstanding. NeoLife primarily focuses on nutritional supplements and wellness products aimed at supporting general health and well-being. However, it's important to note that nutritional supplements are not typically intended to treat or cure medical conditions such as hernias.
### Understanding Hernias and Medical Treatment
A hernia occurs when an organ or fatty tissue squeezes through a weak spot or opening in a muscle or connective tissue wall. Common types of hernias include inguinal (groin), umbilical (belly button), and hiatal (upper stomach) hernias. Hernias often require medical intervention, such as surgery, to repair the weakened area and prevent potential complications.
### NeoLife's Approach to Health and Wellness
NeoLife focuses on providing high-quality nutritional supplements and wellness products that support overall health, including cardiovascular health, immune support, weight management, and more. Their products are formulated based on scientific research and are designed to complement a healthy lifestyle.
### How NeoLife Can Support Overall Health
While NeoLife products may not directly treat hernias, they can contribute to overall health and well-being in several ways:
1. **Nutritional Support**: NeoLife offers a range of supplements rich in vitamins, minerals, antioxidants, and essential nutrients that support various bodily functions. Maintaining overall health can indirectly support recovery from surgery or medical treatments.
2. **Immune System Support**: Supporting a healthy immune system is crucial for recovery from surgeries and reducing the risk of complications. NeoLife supplements like Pro Vitality and NutriShake provide essential nutrients that support immune function.
3. **Wellness and Vitality**: NeoLife promotes a holistic approach to wellness, emphasizing the importance of a balanced diet, regular exercise, and proper nutrition. These factors can contribute to overall well-being and may support recovery and healing processes.
### Seeking Medical Advice
It's important to consult with healthcare professionals for medical conditions like hernias. Medical treatments such as surgery are typically required to repair hernias and prevent potential complications. While nutritional supplements can play a supportive role in overall health, they should not replace medical treatment prescribed by qualified healthcare providers.
### Conclusion
NeoLife is dedicated to promoting health and wellness through quality nutritional supplements and lifestyle products. While their products are not intended to treat specific medical conditions such as hernias, they can support overall health and well-being. For individuals dealing with hernias or any medical condition, seeking appropriate medical advice and treatment remains essential. Embrace a balanced approach to health with NeoLife's products and prioritize your well-being with professional medical guidance when needed.
### Strengthening Bones with NeoLife: A Comprehensive Approach to Skeletal Health
Maintaining strong and healthy bones is essential for overall well-being and mobility throughout life. NeoLife, a trusted name in nutritional supplements and wellness products, offers a range of scientifically formulated supplements designed to support bone health. Let's explore how NeoLife products can contribute to bone strength and vitality.
#### The Importance of Bone Health
Bones are more than just a structural framework for the body; they also protect organs, store minerals like calcium and phosphorus, and provide a mineral reservoir for the body. As we age, bone density can decrease, leading to conditions like osteoporosis and an increased risk of fractures. Factors such as diet, physical activity, and hormonal changes influence bone health.
#### NeoLife's Approach to Bone Health
NeoLife products are developed with a focus on providing essential nutrients that support bone strength and density. Here are some key supplements and their roles in promoting bone health:
1. **NeoLife Chelated Cal-Mag with Vitamin D**
Calcium and magnesium are crucial minerals for bone health, supporting bone density and strength. Vitamin D enhances calcium absorption and helps maintain proper calcium levels in the bloodstream. NeoLife's Chelated Cal-Mag with Vitamin D provides these essential nutrients in a highly bioavailable form to support optimal bone health.
2. **NeoLife Pro Vitality**
Pro Vitality is a daily nutritional supplement pack that includes vitamins, minerals, and phytonutrients essential for overall health, including bone health. Nutrients like vitamin K, which supports calcium utilization in bones, and vitamin C, important for collagen formation in bone tissue, contribute to maintaining strong and resilient bones.
3. **NeoLife Salmon Oil Plus**
Omega-3 fatty acids found in fish oil, such as those in NeoLife Salmon Oil Plus, may have benefits for bone health. Studies suggest that omega-3s can help reduce inflammation and promote bone density, potentially lowering the risk of osteoporosis and fractures.
4. **NeoLife Cruciferous Plus**
This supplement contains phytonutrients from cruciferous vegetables like broccoli, kale, and cabbage. These vegetables are rich in vitamins, minerals, and antioxidants that support overall bone health by promoting a healthy inflammatory response and providing essential nutrients.
#### Lifestyle Factors for Bone Health
In addition to nutritional supplements, NeoLife emphasizes the importance of lifestyle factors that contribute to bone health:
- **Regular Exercise**: Weight-bearing exercises like walking, jogging, and resistance training help build and maintain bone density.
- **Balanced Diet**: A diet rich in calcium, magnesium, vitamin D, and other essential nutrients supports bone health. Include dairy products, leafy greens, nuts, and fortified foods in your diet.
- **Avoiding Risk Factors**: Limiting alcohol intake, avoiding smoking, and maintaining a healthy weight can help protect bone health and reduce the risk of osteoporosis.
#### NeoLife's Commitment to Quality
NeoLife products are formulated based on scientific research and quality standards. The company emphasizes the importance of using bioavailable ingredients and conducting rigorous testing to ensure product efficacy and safety. By choosing NeoLife supplements for bone health, individuals can trust that they are supporting their skeletal system with high-quality nutrients.
#### Conclusion
NeoLife offers a comprehensive approach to supporting bone health through a range of nutritional supplements designed to provide essential nutrients and support overall well-being. Whether you're looking to maintain bone density, support bone strength, or reduce the risk of osteoporosis, NeoLife products can play a valuable role in your daily wellness regimen. Embrace a proactive approach to bone health with NeoLife and prioritize your skeletal well-being for a healthier, more active lifestyle.
NeoLife Full Motion is formulated with a blend of key ingredients aimed at supporting joint health and mobility. Here are the primary ingredients commonly found in NeoLife Full Motion:
1. **Glucosamine Hydrochloride**:
- A naturally occurring compound that plays a crucial role in maintaining healthy cartilage. It helps in the repair and maintenance of cartilage, promoting joint flexibility and comfort.
2. **Herbal Comfort Complex**:
- **Turmeric (Curcuma longa)**: Known for its anti-inflammatory and antioxidant properties, turmeric helps to reduce inflammation and pain in the joints.
- **Boswellia (Boswellia serrata)**: Also known as Indian frankincense, Boswellia is used for its anti-inflammatory effects and its ability to support joint health and reduce pain.
3. **Vitamin C (Ascorbic Acid)**:
- An essential vitamin that aids in collagen synthesis, which is important for maintaining the integrity of cartilage and supporting joint health. It also acts as an antioxidant, protecting cells from damage.
4. **Manganese**:
- A trace mineral that is important for bone health and the formation of connective tissue. It also plays a role in the synthesis of cartilage components.
5. **Bromelain**:
- An enzyme derived from pineapples that has anti-inflammatory properties and can help reduce swelling and pain in the joints.
6. **Other Supportive Ingredients**:
- May include additional vitamins, minerals, and natural extracts that support overall joint health and enhance the bioavailability of the primary ingredients.
These ingredients work synergistically to provide comprehensive support for joint health, reduce inflammation and discomfort, and promote mobility and flexibility. The combination of glucosamine, anti-inflammatory herbs, and essential nutrients makes NeoLife Full Motion an effective supplement for maintaining healthy joints and an active lifestyle. Always check the product label for the most accurate and detailed list of ingredients.
**Unlocking Radiant Skin with NeoLife: A Journey into Advanced Skincare**
In our quest for timeless beauty and healthy skin, the skincare industry continually evolves, introducing groundbreaking innovations to transform our complexion. Among these innovations, NeoLife emerges as a beacon of scientific excellence, promising not just skincare, but a holistic approach to radiant living.
### Understanding NeoLife: More than Skin Deep
NeoLife isn't just another skincare brand; it's a philosophy—a commitment to harnessing nature's potent ingredients and combining them with cutting-edge science. At its core lies a profound understanding of the skin's biology and the belief that true beauty emanates from within.
### The Science Behind NeoLife
Central to NeoLife's approach is its dedication to scientific research. Each product is meticulously formulated using state-of-the-art technologies and is backed by extensive clinical studies. From the finest botanical extracts to advanced peptides and antioxidants, every ingredient is chosen for its efficacy and safety, ensuring visible results without compromise.
### A Journey to Radiance: The NeoLife Skincare Routine
Embracing NeoLife is embarking on a journey to discover a skincare routine tailored to individual needs. Whether combating signs of aging, addressing specific skin concerns, or maintaining youthful vitality, NeoLife offers a comprehensive range of products designed to deliver transformative results.
1. **Cleansing and Prep**: Begin your skincare ritual with gentle yet effective cleansers that purify without stripping essential oils. NeoLife's cleansers are enriched with botanical extracts to nourish and prepare the skin for subsequent treatments.
2. **Targeted Treatments**: Address specific concerns such as fine lines, wrinkles, dark spots, and uneven texture with targeted serums and treatments. NeoLife's formulations penetrate deep into the skin, delivering active ingredients where they are needed most.
3. **Hydration and Protection**: Nourish and protect your skin with NeoLife's luxurious moisturizers and SPF formulations. These products not only hydrate and replenish but also shield against environmental aggressors, ensuring your skin remains youthful and vibrant.
4. **Nighttime Regeneration**: Overnight, aid your skin's natural repair process with NeoLife's specialized night creams and treatments. These products work tirelessly while you sleep, promoting cell turnover and rejuvenation.
### NeoLife: Beyond Skincare
Beyond its exceptional skincare offerings, NeoLife advocates for a holistic approach to beauty and wellness. Their philosophy extends to nutritional supplements that support skin health from within. By nourishing the body with essential vitamins, minerals, and antioxidants, NeoLife reinforces the foundation of healthy, glowing skin.
### The NeoLife Community: Empowering Beauty
NeoLife isn't just a brand; it's a community of individuals committed to empowering each other through knowledge and support. With personalized skincare consultations and educational resources, NeoLife ensures that every customer embarks on a skincare journey that is as unique as they are.
### Conclusion: Embrace Your Radiance with NeoLife
In a world where skincare choices abound, NeoLife stands out as a beacon of excellence and innovation. By blending nature's bounty with scientific rigor, NeoLife offers more than skincare—it offers a path to radiant living. Whether you're seeking to reverse the signs of aging, address specific concerns, or simply maintain your skin's health, NeoLife invites you to embark on a transformative journey towards timeless beauty.
Embrace NeoLife. Embrace radiance.
**
In the pursuit of timeless beauty and youthful vitality, NeoLife emerges as a beacon of innovation in the realm of anti-aging skincare. Rooted in a commitment to scientific rigor and natural efficacy, NeoLife's products are meticulously crafted to rejuvenate and restore the skin, offering a comprehensive solution to combat the signs of aging.
### The Science Behind NeoLife Anti-Aging Products
At the heart of NeoLife's anti-aging philosophy lies a deep understanding of skin biology and the aging process. Each product is formulated with precision, utilizing advanced technologies and clinically proven ingredients to target specific concerns such as fine lines, wrinkles, loss of elasticity, and uneven skin tone.
NeoLife integrates powerful botanical extracts, potent antioxidants, peptides, and vitamins into their formulations. These ingredients work synergistically to stimulate collagen production, enhance skin firmness, improve hydration levels, and protect against environmental stressors that accelerate aging.
### Key Products in the NeoLife Anti-Aging Range
1. **Age-Defying Serums**: NeoLife offers a range of serums enriched with concentrated active ingredients. These serums penetrate deep into the skin, delivering nutrients that promote cell regeneration and diminish the appearance of wrinkles and fine lines.
2. **Firming Moisturizers**: Designed to lift and firm the skin, NeoLife's moisturizers are infused with peptides and hydrating agents to restore elasticity and resilience. They provide essential moisture while combating sagging and promoting a more youthful contour.
3. **Targeted Treatments**: NeoLife's targeted treatments address specific aging concerns, such as dark spots, hyperpigmentation, and dullness. Formulated with brightening agents and exfoliants, these treatments reveal a smoother, more radiant complexion.
4. **Night Renewal Creams**: Overnight, NeoLife's night creams work to repair and regenerate the skin. Packed with nourishing botanicals and anti-aging peptides, these creams support the skin's natural renewal process, ensuring you wake up to visibly rejuvenated skin.
### The NeoLife Difference: Beyond Skincare
NeoLife transcends traditional skincare by advocating for holistic wellness. Their products are complemented by nutritional supplements that support overall health and vitality, reinforcing the skin's resilience from within. By nourishing the body with essential vitamins, minerals, and antioxidants, NeoLife ensures a comprehensive approach to anti-aging that addresses both external and internal factors.
### The NeoLife Commitment: Science, Sustainability, and Community
NeoLife not only prioritizes scientific excellence but also upholds principles of sustainability and community empowerment. Their commitment to environmental responsibility ensures that every product is ethically sourced and produced. Moreover, NeoLife fosters a supportive community through personalized skincare consultations and educational resources, empowering individuals to make informed choices about their anti-aging regimen.
### Embrace Youthful Radiance with NeoLife
In a world where beauty standards evolve, NeoLife stands as a testament to innovation and efficacy in anti-aging skincare. Whether you're seeking to diminish fine lines, restore firmness, or enhance overall skin health, NeoLife invites you to embark on a transformative journey towards radiant, youthful skin.
Embrace NeoLife. Embrace timeless beauty.
**NeoLife: Nurturing Digestive Health Through Scientific Excellence**
In the pursuit of overall wellness, digestive health plays a pivotal role in our daily lives. Recognizing this fundamental connection, NeoLife has crafted a comprehensive range of products designed to support and enhance digestive function through a blend of scientific innovation and natural ingredients. Whether you're seeking relief from occasional digestive discomfort or aiming to optimize your gut health, NeoLife offers solutions that prioritize efficacy, safety, and holistic well-being.
### Understanding Digestive Health with NeoLife
Digestive health is more than just the absence of discomfort; it's about achieving a harmonious balance within the gastrointestinal system. NeoLife understands this complexity and approaches digestive wellness with a deep-rooted commitment to scientific research and formulation. Each product is meticulously crafted to address specific digestive concerns, offering targeted solutions backed by clinical studies and rigorous testing.
### Key Products for Digestive Wellness
1. **Probiotics**: NeoLife's probiotic supplements are formulated with strains that support gut flora balance and promote digestive regularity. These beneficial bacteria play a crucial role in maintaining intestinal health, enhancing nutrient absorption, and supporting immune function.
2. **Digestive Enzymes**: Designed to aid in the breakdown of fats, proteins, and carbohydrates, NeoLife's digestive enzyme supplements support optimal digestion and nutrient absorption. These enzymes help alleviate occasional digestive discomfort and promote overall digestive efficiency.
3. **Fiber Supplements**: NeoLife offers fiber supplements derived from natural sources such as fruits, vegetables, and grains. These supplements help support healthy bowel function, regulate digestion, and promote a feeling of fullness, aiding in weight management and overall gut health.
4. **Herbal Blends**: NeoLife incorporates herbal blends known for their digestive benefits, such as peppermint, ginger, and fennel, into some of their products. These botanicals provide soothing relief from occasional indigestion, bloating, and gas, promoting comfort and digestive balance.
### The NeoLife Approach: Integrating Science and Nature
NeoLife's commitment to digestive health extends beyond individual products; it embodies a philosophy of integrating science and nature to optimize well-being. Their formulations combine the latest scientific advancements with time-tested natural remedies, ensuring effective results without compromising on safety or quality.
### Beyond Digestive Supplements: A Holistic Approach to Wellness
NeoLife advocates for a holistic approach to wellness that encompasses nutrition, exercise, and lifestyle choices. In addition to digestive supplements, NeoLife offers a wide range of nutritional products that support overall health and vitality. By nourishing the body with essential vitamins, minerals, and antioxidants, NeoLife empowers individuals to achieve optimal health from the inside out.
### NeoLife: Empowering Wellness and Community
More than a brand, NeoLife fosters a community of individuals committed to achieving and maintaining vibrant health. Through personalized wellness consultations, educational resources, and a supportive network, NeoLife empowers individuals to take charge of their digestive health journey.
### Embrace Digestive Wellness with NeoLife
In a world where digestive health is increasingly recognized as essential to overall well-being, NeoLife stands as a beacon of scientific excellence and holistic care. Whether you're seeking relief from digestive discomfort or aiming to optimize your gut health, NeoLife invites you to embark on a journey towards improved digestion and enhanced vitality.
Embrace NeoLife. Embrace digestive wellness.
**NeoLife: Elevating Wellness with Scientifically Advanced Products**
In the pursuit of holistic well-being, NeoLife emerges as a cornerstone of innovation, offering a diverse array of products meticulously crafted to support every facet of wellness. From nutritional supplements to skincare solutions, NeoLife integrates cutting-edge science with nature's bounty, empowering individuals to achieve optimal health and vitality.
### The Science Behind NeoLife Wellness Products
NeoLife's commitment to scientific rigor is evident in every product they offer. Each formulation is backed by extensive research and clinical studies, ensuring efficacy and safety. Whether addressing nutritional deficiencies, supporting immune function, or enhancing skin health, NeoLife products are designed to deliver tangible benefits that promote overall wellness.
### Key Categories of NeoLife Wellness Products
1. **Nutritional Supplements**: NeoLife's nutritional supplements encompass a wide range of vitamins, minerals, antioxidants, and phytonutrients essential for maintaining optimal health. From daily multivitamins to specialized formulations targeting specific health concerns, these supplements provide comprehensive support for the body's needs.
2. **Weight Management Solutions**: NeoLife offers scientifically formulated products to support healthy weight management. These include meal replacement shakes, metabolism-boosting supplements, and appetite-control formulations designed to promote sustainable weight loss and maintenance.
3. **Immune Support**: Strengthening immune function is crucial for overall wellness. NeoLife's immune support products feature a blend of vitamins, minerals, and botanical extracts known for their immune-boosting properties. These supplements help fortify the body's natural defenses against illness and infection.
4. **Skincare**: Beyond internal health, NeoLife prioritizes skin health with a range of advanced skincare products. Formulated with potent antioxidants, peptides, and botanical extracts, NeoLife skincare supports cellular rejuvenation, hydration, and protection against environmental stressors, promoting radiant and youthful-looking skin.
### NeoLife's Holistic Approach to Wellness
NeoLife advocates for a holistic approach to wellness that goes beyond supplementation. Their philosophy emphasizes the importance of balanced nutrition, regular physical activity, adequate rest, and mindfulness. By integrating these principles into daily life, NeoLife empowers individuals to achieve long-term health and vitality.
### Community and Support
More than a product provider, NeoLife fosters a supportive community dedicated to wellness education and empowerment. Through personalized wellness consultations, educational resources, and a network of like-minded individuals, NeoLife ensures that each customer receives the guidance and encouragement needed to embark on their wellness journey confidently.
### Embrace Wellness with NeoLife
In a world where optimal health is a priority, NeoLife stands at the forefront, offering scientifically advanced products that promote holistic wellness. Whether you're looking to enhance your nutritional intake, support immune function, manage weight effectively, or rejuvenate your skin, NeoLife invites you to embrace a lifestyle of vitality and well-being.
Embrace NeoLife. Embrace holistic wellness.
**NeoLife: Empowering Health and Wellness Through Science and Nature**
In today's fast-paced world, achieving and maintaining optimal health and wellness is a universal aspiration. NeoLife, a leader in the health and wellness industry, stands as a beacon of scientific excellence and holistic care, offering a diverse range of products and a supportive community dedicated to enhancing every aspect of well-being.
### The Science Behind NeoLife's Approach
At the core of NeoLife's philosophy lies a commitment to scientific research and innovation. Each product is meticulously formulated using cutting-edge technologies and the highest quality natural ingredients. Backed by decades of scientific expertise and clinical studies, NeoLife products are designed to deliver measurable results that support overall health, vitality, and longevity.
### Comprehensive Wellness Solutions
NeoLife offers a comprehensive suite of wellness solutions that address key pillars of health:
1. **Nutritional Supplements**: NeoLife's nutritional supplements are crafted to fill nutrient gaps in modern diets. From daily multivitamins to targeted supplements supporting heart health, bone health, and cognitive function, NeoLife products provide essential vitamins, minerals, antioxidants, and phytonutrients needed for optimal wellness.
2. **Weight Management**: NeoLife recognizes the importance of healthy weight management in achieving overall wellness. Their weight management solutions include meal replacement shakes, metabolism-boosting supplements, and programs designed to support sustainable weight loss and maintenance.
3. **Immune Support**: Strengthening immune function is crucial, especially in challenging times. NeoLife's immune support products are formulated with immune-boosting vitamins, minerals, and botanical extracts to enhance the body's natural defenses against illness and promote resilience.
4. **Digestive Health**: NeoLife promotes digestive wellness with probiotics, digestive enzymes, and fiber supplements that support gut health, aid in digestion, and promote regularity.
5. **Skincare**: NeoLife extends its commitment to wellness to skincare with products that nourish and protect the skin. Formulated with potent antioxidants, peptides, and botanical extracts, NeoLife skincare promotes cellular rejuvenation, hydration, and a radiant complexion.
### Holistic Wellness Philosophy
NeoLife advocates for a holistic approach to wellness that encompasses nutrition, physical activity, rest, and emotional well-being. They believe that true wellness is achieved through a balanced lifestyle and empower their community with educational resources, personalized consultations, and ongoing support.
### The NeoLife Community
Beyond products, NeoLife fosters a vibrant community of wellness enthusiasts and advocates. Through wellness events, educational seminars, and online forums, NeoLife connects like-minded individuals who are passionate about health, encouraging them to share experiences, support each other's journeys, and celebrate achievements together.
### Embrace Health and Wellness with NeoLife
In a world where health is a precious asset, NeoLife stands as a trusted partner on the journey to wellness. Whether you're looking to optimize your nutrition, support immune function, manage weight effectively, or enhance your skincare routine, NeoLife offers the resources, products, and community support needed to live a life of vitality and well-being.
Embrace NeoLife. Embrace health and wellness.
**NeoLife Green Liquid Soap: Elevating Cleanliness with Natural Excellence**
In the realm of personal hygiene, choosing the right soap goes beyond mere cleansing—it's about nourishing the skin while ensuring effective protection against germs and environmental impurities. NeoLife, renowned for its commitment to scientific rigor and natural ingredients, introduces the NeoLife Green Liquid Soap, a product that embodies their dedication to quality, safety, and environmental responsibility.
### The Essence of NeoLife Green Liquid Soap
NeoLife Green Liquid Soap is not just a soap; it's a testament to NeoLife's ethos of integrating science with nature. Formulated with carefully selected botanical extracts and gentle cleansing agents, this soap provides a refreshing and invigorating cleansing experience while respecting the skin's natural balance.
### Key Features and Benefits
1. **Natural Ingredients**: NeoLife Green Liquid Soap is enriched with natural botanical extracts known for their soothing and nourishing properties. Ingredients like aloe vera, green tea extract, and chamomile help to moisturize and protect the skin, making it ideal for daily use.
2. **Gentle Cleansing**: The soap is designed to cleanse effectively without stripping the skin of its natural oils. Its mild formulation makes it suitable for all skin types, including sensitive skin, ensuring a gentle and comfortable cleansing experience.
3. **Antibacterial Protection**: NeoLife Green Liquid Soap provides reliable antibacterial protection, helping to eliminate germs and reduce the risk of infections. This makes it a practical choice for maintaining cleanliness and hygiene in everyday routines.
4. **Environmentally Conscious**: NeoLife is committed to sustainability, and the Green Liquid Soap reflects this commitment. The packaging is designed to minimize environmental impact, using recyclable materials whenever possible.
### Applications and Versatility
NeoLife Green Liquid Soap is versatile and can be used in various settings:
- **Personal Use**: Ideal for handwashing at home, in the workplace, or while traveling, ensuring clean and refreshed hands.
- **Hygiene Practices**: Suitable for use in public facilities, schools, and healthcare settings where effective cleansing and germ protection are essential.
- **Family-Friendly**: Safe for the whole family, including children and individuals with sensitive skin, promoting good hygiene habits from an early age.
### The NeoLife Promise
NeoLife Green Liquid Soap exemplifies NeoLife's commitment to quality, safety, and efficacy. Each batch undergoes stringent quality control measures to ensure consistency and performance, providing consumers with a product they can trust for their daily hygiene needs.
### Embrace Cleanliness with NeoLife
In a world where hygiene is paramount, NeoLife Green Liquid Soap stands out as a choice that not only cleans effectively but also cares for your skin and the environment. Whether you're looking for a gentle soap for everyday use or seeking a reliable antibacterial solution, NeoLife Green Liquid Soap offers the perfect blend of natural goodness and scientific excellence.
Experience NeoLife. Experience cleanliness with care.
**NeoLife PhytoDefense: Enhancing Immune Support with Nature’s Armor**
In the ongoing pursuit of robust health and vitality, supporting our immune system is paramount. NeoLife, a pioneer in nutritional wellness, introduces PhytoDefense—a powerhouse supplement crafted to fortify the body's natural defenses with a potent blend of botanicals and antioxidants. Backed by scientific research and a commitment to quality, NeoLife PhytoDefense embodies excellence in immune support, empowering individuals to thrive in today's demanding world.
### Understanding NeoLife PhytoDefense
NeoLife PhytoDefense is a comprehensive dietary supplement formulated to strengthen immune function and promote overall well-being. It harnesses the synergistic benefits of natural plant extracts and antioxidants to protect cells from oxidative stress and support optimal immune response.
### Key Ingredients and Benefits
1. **Botanical Extracts**: PhytoDefense features a blend of botanical extracts such as grape seed extract, citrus bioflavonoids, and olive fruit extract. These ingredients are rich in antioxidants known to neutralize free radicals and reduce inflammation, thereby supporting immune health and longevity.
2. **Vitamins and Minerals**: The supplement is fortified with essential vitamins and minerals, including vitamin C, vitamin E, selenium, and zinc. These nutrients play crucial roles in immune function, helping to enhance resistance against infections and promote immune system balance.
3. **Antioxidant Protection**: NeoLife PhytoDefense provides robust antioxidant support, helping to protect cells from oxidative damage caused by environmental stressors and aging. This defense mechanism supports overall cellular health and contributes to a stronger immune response.
4. **Immune Modulation**: By promoting a balanced immune response, PhytoDefense helps regulate immune activity without overstimulation. This modulation is essential for maintaining immune resilience and adapting to varying health challenges.
### Scientific Rigor and Quality Assurance
NeoLife adheres to stringent quality control measures in the sourcing and manufacturing of PhytoDefense. Each ingredient undergoes rigorous testing to ensure purity, potency, and efficacy. This commitment to excellence guarantees that every NeoLife product, including PhytoDefense, meets the highest standards of safety and effectiveness.
### Integrating PhytoDefense into Your Wellness Routine
NeoLife PhytoDefense is designed for individuals seeking proactive immune support:
- **Daily Wellness**: Incorporate PhytoDefense into your daily regimen to fortify immune defenses and promote overall health.
- **Seasonal Support**: During times of increased immune challenge, such as seasonal changes or stressful periods, PhytoDefense provides added reinforcement.
- **Travel and Exposure**: Support immune resilience when traveling or in environments where exposure to germs is heightened.
### NeoLife: Beyond Immune Support
Beyond immune health, NeoLife advocates for holistic wellness through education, community support, and a commitment to sustainable practices. Their approach empowers individuals to make informed choices and embrace a lifestyle of vitality and well-being.
### Embrace Immune Resilience with NeoLife PhytoDefense
In a world where health is a priority, NeoLife PhytoDefense stands as a testament to scientific innovation and natural wellness. Whether you're proactively supporting your immune system or seeking to fortify your health defenses, NeoLife PhytoDefense offers a reliable solution backed by decades of nutritional expertise.
Experience NeoLife. Embrace immune resilience with nature’s armor.
**NeoLife PhytoDefense: Enhancing Immune Support with Nature’s Armor**
In the ongoing pursuit of robust health and vitality, supporting our immune system is paramount. NeoLife, a pioneer in nutritional wellness, introduces PhytoDefense—a powerhouse supplement crafted to fortify the body's natural defenses with a potent blend of botanicals and antioxidants. Backed by scientific research and a commitment to quality, NeoLife PhytoDefense embodies excellence in immune support, empowering individuals to thrive in today's demanding world.
### Understanding NeoLife PhytoDefense
NeoLife PhytoDefense is a comprehensive dietary supplement formulated to strengthen immune function and promote overall well-being. It harnesses the synergistic benefits of natural plant extracts and antioxidants to protect cells from oxidative stress and support optimal immune response.
### Key Ingredients and Benefits
1. **Botanical Extracts**: PhytoDefense features a blend of botanical extracts such as grape seed extract, citrus bioflavonoids, and olive fruit extract. These ingredients are rich in antioxidants known to neutralize free radicals and reduce inflammation, thereby supporting immune health and longevity.
2. **Vitamins and Minerals**: The supplement is fortified with essential vitamins and minerals, including vitamin C, vitamin E, selenium, and zinc. These nutrients play crucial roles in immune function, helping to enhance resistance against infections and promote immune system balance.
3. **Antioxidant Protection**: NeoLife PhytoDefense provides robust antioxidant support, helping to protect cells from oxidative damage caused by environmental stressors and aging. This defense mechanism supports overall cellular health and contributes to a stronger immune response.
4. **Immune Modulation**: By promoting a balanced immune response, PhytoDefense helps regulate immune activity without overstimulation. This modulation is essential for maintaining immune resilience and adapting to varying health challenges.
### Scientific Rigor and Quality Assurance
NeoLife adheres to stringent quality control measures in the sourcing and manufacturing of PhytoDefense. Each ingredient undergoes rigorous testing to ensure purity, potency, and efficacy. This commitment to excellence guarantees that every NeoLife product, including PhytoDefense, meets the highest standards of safety and effectiveness.
### Integrating PhytoDefense into Your Wellness Routine
NeoLife PhytoDefense is designed for individuals seeking proactive immune support:
- **Daily Wellness**: Incorporate PhytoDefense into your daily regimen to fortify immune defenses and promote overall health.
- **Seasonal Support**: During times of increased immune challenge, such as seasonal changes or stressful periods, PhytoDefense provides added reinforcement.
- **Travel and Exposure**: Support immune resilience when traveling or in environments where exposure to germs is heightened.
### NeoLife: Beyond Immune Support
Beyond immune health, NeoLife advocates for holistic wellness through education, community support, and a commitment to sustainable practices. Their approach empowers individuals to make informed choices and embrace a lifestyle of vitality and well-being.
### Embrace Immune Resilience with NeoLife PhytoDefense
In a world where health is a priority, NeoLife PhytoDefense stands as a testament to scientific innovation and natural wellness. Whether you're proactively supporting your immune system or seeking to fortify your health defenses, NeoLife PhytoDefense offers a reliable solution backed by decades of nutritional expertise.
Experience NeoLife. Embrace immune resilience with nature’s armor.
**Unlocking Wellness: Exploring NeoLife PhytoDefense Ingredients**
NeoLife PhytoDefense stands at the forefront of immune support supplements, offering a robust blend of natural ingredients carefully selected for their immune-boosting properties. Rooted in scientific research and bolstered by years of nutritional expertise, PhytoDefense combines potent botanical extracts, antioxidants, vitamins, and minerals to fortify the body's defenses and promote overall well-being. Let's delve into the key ingredients that make PhytoDefense a cornerstone of immune health.
### Key Ingredients in NeoLife PhytoDefense
1. **Grape Seed Extract**: Known for its high concentration of polyphenols, grape seed extract is a powerful antioxidant that scavenges free radicals, protecting cells from oxidative stress. It supports cardiovascular health and enhances immune function by bolstering the body's natural defenses.
2. **Citrus Bioflavonoids**: Derived from citrus fruits, bioflavonoids are antioxidants that work synergistically with vitamin C to strengthen capillaries, reduce inflammation, and support immune response. They contribute to overall cardiovascular health and promote collagen synthesis for skin elasticity.
3. **Olive Fruit Extract**: Rich in phenolic compounds, olive fruit extract exhibits potent antioxidant and anti-inflammatory properties. It helps protect against oxidative damage, supports cardiovascular health, and enhances immune function by modulating inflammatory responses.
4. **Vitamins and Minerals**:
- **Vitamin C**: Essential for immune function, vitamin C stimulates the production of white blood cells and antibodies, vital components of the immune system's defense against pathogens.
- **Vitamin E**: Another powerful antioxidant, vitamin E protects cell membranes from damage and enhances immune function by neutralizing free radicals.
- **Selenium**: Acts as a cofactor for antioxidant enzymes, selenium supports immune health and helps regulate thyroid function and metabolism.
- **Zinc**: Plays a crucial role in immune response, zinc is involved in the activation and function of immune cells and supports wound healing and cellular repair.
5. **Carotenoids**: Found in fruits and vegetables, carotenoids like beta-carotene are precursors to vitamin A, which supports immune function and promotes healthy vision and skin.
### Synergistic Benefits of PhytoDefense Ingredients
NeoLife PhytoDefense harnesses the synergistic benefits of these ingredients to promote immune resilience and overall health:
- **Antioxidant Protection**: The combined antioxidant power of grape seed extract, citrus bioflavonoids, and olive fruit extract helps neutralize free radicals, protecting cells from oxidative stress and supporting cellular health.
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### Quality Assurance and Safety
Each batch of NeoLife PhytoDefense undergoes rigorous testing and quality control measures to ensure purity, potency, and safety. NeoLife's commitment to excellence guarantees that PhytoDefense delivers consistent and reliable immune support without compromising on quality.
### Conclusion
NeoLife PhytoDefense represents a fusion of nature's finest ingredients and scientific innovation, offering a comprehensive solution to support immune health and overall well-being. By incorporating PhytoDefense into your daily regimen, you can fortify your body's defenses against environmental stressors and enjoy enhanced vitality and resilience.
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**The Dynamic Role of NeoLife PhytoDefense: Fortifying Immune Health**
In an era where maintaining robust immune health is more crucial than ever, NeoLife PhytoDefense emerges as a formidable ally in bolstering the body's natural defenses. Rooted in a blend of potent botanical extracts, antioxidants, and essential nutrients, PhytoDefense works synergistically to support immune function, protect against oxidative stress, and promote overall well-being. Let's explore how this innovative supplement contributes to the dynamic work of enhancing immune resilience.
### Understanding the Mechanism of NeoLife PhytoDefense
NeoLife PhytoDefense is meticulously formulated to harness the power of nature's bounty in promoting immune health:
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2. **Immune Modulation**: PhytoDefense includes essential vitamins like C and E, along with selenium, zinc, and carotenoids. These nutrients play crucial roles in immune function by supporting the production and activity of immune cells, enhancing antibody response, and maintaining immune system balance. This modulation ensures that the immune system responds effectively to pathogens while avoiding excessive inflammation.
3. **Cardiovascular Support**: Many of the botanical extracts in PhytoDefense, such as grape seed extract and citrus bioflavonoids, also benefit cardiovascular health. They promote healthy circulation, reduce inflammation in blood vessels, and support endothelial function, contributing to overall cardiovascular wellness.
### The Impact of PhytoDefense in Supporting Overall Health
NeoLife PhytoDefense goes beyond traditional immune supplements by offering comprehensive health benefits:
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The Viscount Who Loves Me Summary And Reviews
In 1814, after years as one of the most notorious rakes of the ton, Anthony, Viscount Bridgerton, decides to settle down and carry on the family line. Haunted by his father's death at a young age from a bee sting, Anthony now believes, albeit irrationally, that he will die young too, and does not want the complication of falling in love.
Meanwhile, Kate Sheffield arrives in London's ton with her younger half-sister Edwina and her stepmother Mary. She is determined to find a suitable husband for Edwina, who is intelligent and renowned for her beauty, and is less hopeful about her own prospects as a near spinster.
When Anthony begins to court Edwina, Kate is determined to interfere, doubting that he is reformed from his roguish ways. Despite the animosity between the two, a mutual attraction begins to develop when they share a kiss.
While visiting Aubrey Hall, the Bridgertons' country estate, Kate is stung by a bee while with Anthony. He is overcome with fear and attempts to tend the wound; they are caught in a compromising position by their mothers, leading Anthony to declare he will marry Kate to protect their reputations. Society gossip accepts that the viscount was actually courting Kate rather than Edwina. Edwina is happy for them, having suspected both Kate and Anthony's affection. However, Kate struggles with her growing feelings for Anthony as he insists that while he will marry her, he will never love her.
Anthony becomes conflicted when he starts falling in love with his wife. Kate ends up in a carriage accident and Anthony ends up admitting to her that he loves her.
Reception
In March 2022, People ranked The Viscount Who Loved Me, a perennial fan favorite, as the best book of the Bridgerton series for its enemies-to-lovers trope "full of banter and chemistry" with character development for the central couple, "both as a pair and on their own."[3]
#1 New York Times Best Seller[1][2]
USA Today Best Seller List
Publishers Weekly Mass Market Bestseller
New York Times Extended Bestseller list
2001 RITA Awards Nomination in the Long Historical Category
Why We Love Prince Harry
Prince Harry, Duke of Sussex (Henry Charles Albert David; born 15 September 1984) is a member of the British royal family. As the younger son of King Charles III and Diana, Princess of Wales, he is fifth in the line of succession to the British throne.
Educated at Wetherby School, Ludgrove School, and Eton College, Harry completed army officer training at the Royal Military Academy Sandhurst. He was commissioned as a cornet into the Blues and Royals and served temporarily with his elder brother, William. Harry was separately deployed on active duty to Afghanistan on two occasions; the first was in 2007–2008 for ten weeks in Helmand Province. The second was for twenty weeks in 2012–2013 with the Army Air Corps.
Inspired by the Warrior Games in the United States, Harry launched the Invictus Games in 2014 as founding patron and now remains involved in a non-royal capacity. Two years later, alongside his brother William and sister-in-law Catherine, Harry jointly initiated the mental health awareness campaign "Heads Together".
In 2018 Harry was made Duke of Sussex prior to his wedding to American actress Meghan Markle. They have two children: Archie and Lilibet. Harry and Meghan stepped down as working royals in January 2020, moved to Meghan's native Southern California, and launched Archewell Inc., a Beverly Hills-based mix of for-profit and not-for-profit (charitable) business organisations.
In March 2021, Harry sat for Oprah with Meghan and Harry, a much-publicised American television interview with his wife and Oprah Winfrey. The couple filmed Harry & Meghan, a Netflix docuseries, which was released in December 2022.
Bridgerton Season 3
As the rest of the synopsis says, "Penelope's lack of self-confidence causes her attempts on the marriage market to fail spectacularly." Colin now returns from his summer trip with a new look and a lot of confidence. However, he is devastated to find that Penelope, who has always appreciated him for who he is, is giving him the cold shoulder. Hoping to rekindle their friendship, Colin offers to teach Penelope self-confidence so that she can find a husband this season. But when the lesson goes a little too well, Colin is forced to confront whether his feelings for Penelope are really just friendship. To make matters worse for Penelope, she has a falling out with Eloise, who finds new friends in an unexpected place. As Penelope's presence in high society grows, it becomes more and more difficult to keep her alter-ego, Lady Whistledown, a secret.
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Romancing Mr Bridgerton Book Review And Summary
Romancing Mister Bridgerton is a 2002 historical romance novel written by Julia Quinn and published by Avon. It is the fourth novel of Quinn's series of Regency romances about the Bridgerton siblings and tells the story of Colin, the third eldest child of the family.
The novel has been a New York Times, Apple Books, USA Today, and Publishers Weekly bestseller, both at the time of publishing and after the debut of the TV adaptation nearly twenty years later.[1] It is being adapted as the third season of Netflix's Bridgerton series,[2] one of the platform's most popular shows of all time.[3] After the show began airing, book retailers often sold out of the series and hardcover copies of the original books began re-selling at prices as high as $700.[4][5]
The novel takes place in 1824, during the Regency era in London, but includes some flashbacks such as in the prologue. In 1812, 15 year-old Penelope Featherington accidentally caused 20-year-old Colin Bridgerton to fall off his horse into a mud puddle. He laughed it off and she became enamored with him.
In 1813, Penelope made her debut and Lady Whistledown's Society Papers, a thrice-weekly, single-sheet newspaper of society gossip, began to be published by the pseudonym Lady Whistledown. Penelope spent time with Eloise Bridgerton and so occasionally encountered Colin, believing her feelings for him will always be unrequited.
In 1820, Penelope overheard Colin telling his elder brothers that he is "certainly not going to marry Penelope Featherington!" They realized she was there but she played it off with dignity.
Now, in 1824, Penelope is considered a spinster at the age of 28, with her unpleasant mother Portia repeatedly implying that they will live together into their old age. Colin Bridgerton has returned from his frequent travels and Portia wonders if Felicity, the youngest Featherington sister, could marry him. Meanwhile, Colin privately reflects that he travels so much because he is restless and without purpose.
At Violet Bridgerton's birthday party a week later, Colin surprises Penelope as she eats an éclair. While they talk, the cream from the half-eaten éclair falls to the floor. Colin dares Penelope to hide the remaining pastry in a nearby potted plant, which she does. The prickly dowager Lady Danbury talks to the pair and announces a contest to the entire party: whomever can unmask Lady Whistledown will win £1000. The next day, Penelope and the Bridgertons speculate about Lady Whistledown's identity and the strategies one might use to find her.
A few days later, Penelope is waiting in the Bridgerton drawing room, when she sees Colin's travel journal laying open on the table and reads the open pages. Colin catches her and is furious. While gathering his journal, he cuts his hand on a letter opener and Penelope helps him staunch the blood. She apologizes but also reassures him how excellent his writing is. Colin expresses his lack of purpose and complains that Lady Whistledown only refers to him as a charmer and nothing more.
Penelope tries to be sympathetic, but challenges him to see that being universally liked is much better than being a spinster. She tells him that, as a well-off man, he can change his life as he wishes.
Later, Colin recalls the only other time he'd unintentionally insulted Penelope: several years earlier, his mother had begun suggesting Penelope as a potential bride, leading him to protest aloud to his brothers, which Penelope overheard. He decides to apologize at the Smythe-Smith musicale.
Lady Danbury muses that Penelope could be Lady Whistledown. After the performance, Colin and Penelope apologize to each other. Penelope encourages him to publish his travel journals.
Two days later, Colin visits Penelope to share his suspicion that Eloise is Lady Whistledown. They argue and then share a kiss.
A few days later, Lady Whistledown announces her retirement in her Society Papers. At that evening's ball, Colin arrives intending to apologize to Penelope, when Cressida Twombley (née Cowper) announces that she herself is Lady Whistledown.
When Cressida tries to collect the £1000, Lady Danbury does not believe her and demands proof.
The next day, Colin heads to Penelope's home to make his apology, when he witnesses her climbing into a hired hack alone. He has his carriage follow her to St. Bride's church in the East End, where he sees her hide an envelope in a pew. He confronts her, reads it, and learns that Penelope herself is Lady Whistledown, writing one last column to denounce Cressida's lie.
They get in his carriage to go back to Mayfair, arguing intensely. In their passion and in such close quarters, they begin to kiss again. When they exit
the carriage at Penelope's home, he proposes to her. They go inside so Colin can ask her mother. Lady Featherington instantly misinterprets Colin's presence as an intention to propose to Felicity and misses numerous hints to the contrary.
A few days later, Penelope and Eloise are chatting about the engagement announcement. While Eloise is happy about Penelope's engagement, it has also made her reevaluate her own choice not to marry. She continues to be evasive about who she is writing letters to. After another amorous encounter with Penelope, Colin visits his younger sister Daphne to seek advice about love.
Cressida has figured out Lady Whistledown's identity and tries to blackmail Penelope, giving her one week to pay £10,000. Penelope lets Colin know, they argue about what to do, and he leaves to set a plan in motion. On their way to Hastings House, the Bridgerton ladies tell Penelope they've been instructed to stick to her like glue. At the ball, Colin makes an announcement about how brilliant Penelope is and reveals that she is Lady Whistledown. Cressida is furious, while those in attendance burst into applause.
In the epilogue, Penelope and Colin receive his newly published travel memoir while she is working on a novel called The Wallflower.
The Fight Against Human Trafficking
Human trafficking is the trade of humans for the purpose of forced labour, sexual slavery, or commercial sexual exploitation.[1]
Human trafficking can occur within a country or trans-nationally. It is distinct from people smuggling, which is characterized by the consent of the person being smuggled.
Human trafficking is condemned as a violation of human rights by international conventions, but legal protection varies globally. The practice has millions of victims around the world.
Child labour is a form of work that may be hazardous to the physical, mental, spiritual, moral, or social development of children and can interfere with their education. According to the International Labour Organization, the global number of children involved in child labour fell during the twelve years to 2012 – it has declined by one third, from 246 million in 2000 to 168 million children in 2012.[33] Sub-Saharan Africa is the region with the highest incidence of child labour, while the largest numbers of child-workers are found in Asia and the Pacific.[33]
IOM statistics indicate that a significant minority (35%) of trafficked persons it assisted in 2011 were less than 18 years of age, which is roughly consistent with estimates from previous years. It was reported in 2010 that Thailand and Brazil were considered to have the worst child sex trafficking records.[34]
Traffickers in children may take advantage of the parents' extreme poverty. Parents may sell children to traffickers in order to pay off debts or gain income, or they may be deceived concerning the prospects of training and a better life for their children. They may sell their children into labour, sex trafficking, or illegal adoptions, although scholars have urged a nuanced understanding and approach to the issue - one that looks at broader socio-economic and political contexts.[35][36][37]
The adoption process, legal and illegal, when abused can sometimes result in cases of trafficking of babies and pregnant women around the world.[38] In David M. Smolin's 2005 papers on child trafficking and adoption scandals between India and the United States,[39][40] he presents the systemic vulnerabilities in the inter-country adoption system that makes adoption scandals predictable.
The United Nations Convention on the Rights of the Child at Article 34, states, "States Parties undertake to protect the child from all forms of sexual exploitation and sexual abuse".[41] In the European Union, commercial sexual exploitation of children is subject to a directive – Directive 2011/92/EU of the European Parliament and of the Council of 13 December 2011 on combating the sexual abuse and sexual exploitation of children and child pornography.[42]
The Hague Convention on Protection of Children and Co-operation in Respect of Intercountry Adoption (or Hague Adoption Convention) is an international convention dealing with international adoption, that aims at preventing child laundering, child trafficking, and other abuses related to international adoption.[43]
The Optional Protocol on the Involvement of Children in Armed Conflict seeks to prevent forceful recruitment (e.g. by guerrilla forces) of children for use in armed conflicts.[44]
Forced marriages have been described as a form of human trafficking in certain situations and certain countries, such as China and its Southeast Asian neighbours from which many women are moved to China, sometimes through promises of work, and forced to marry Chinese men. Ethnographic research with women from Myanmar[54] and Cambodia[55] found that many women eventually get used to their life in China and prefer it to the one they had in their home countries. Furthermore, legal scholars have noted that transnational marriage brokering was never intended to be considered trafficking by the drafters of the Palermo Protocol.
forced labour in the sex industry affects 4.5 million people worldwide.[45] Most victims find themselves in coercive or abusive situations from which escape is both difficult and dangerous.[46]
Trafficking for sexual exploitation was formerly thought of as the organized movement of people, usually women, between countries and within countries for sex work with the use of physical coercion, deception and bondage through forced debt. However, the Trafficking Victims Protection Act of 2000 (US)[47] does not require movement for the offence. The issue becomes contentious when the element of coercion is removed from the definition to incorporate facilitation of consensual involvement in prostitution. For example, in the United Kingdom, the Sexual Offences Act 2003 incorporated trafficking for sexual exploitation but did not require those committing the offence to use coercion, deception or force, so that it also includes any person who enters the UK to carry out sex work with consent as having been "trafficked".[48] In addition, any minor involved in a commercial sex act in the US while under the age of 18 qualifies as a trafficking victim, even if no force, fraud or coercion is involved, under the definition of "Severe Forms of Trafficking in Persons" in the US Trafficking Victims Protection Act of 2000.[49]
Trafficked women and children are often promised work in the domestic or service industry, but instead are sometimes taken to brothels where they are required to undertake sex work, while their passports and other identification papers are confiscated. They may be beaten or locked up and promised their freedom only after earning – through prostitution – their purchase price, as well as their travel and visa costs.[50][51]
On The Way To The Wedding Bridgerton Book Series Summary And Reviews
On the Way to the Wedding is a 2006 historical romance written by Julia Quinn, published by Avon.[1][2] It is the eighth and final novel of Quinn's Bridgerton series[1][3] set in Regency England and tells the story of Gregory, the youngest male Bridgerton sibling.
The hero of the novel is Gregory Bridgerton, the youngest male and last unmarried sibling in the Bridgerton family. After catching a glimpse of the "breathtakingly perfect curve of her neck" at a house party,[3] Gregory falls immediately in love with the beautiful and extremely sought-after Hermione Watson. After he makes his attraction known, Hermione's best friend, the pretty-but-not-quite-as-attractive Lady Lucinda "Lucy" Abernathy informs him that Hermione is already in love, but with someone unsuitable - her father's secretary. Believing that Gregory is more sincere in his attempts to gain Hermione's favor than her other suitors, Lucy agrees to help him win Hermione's heart.
During the course of the house party, Lucy and Gregory become friends and then develop romantic feelings for each other. The author details Gregory's difficulty in determining whether his love for Lucy is real, or if it is simply an infatuation such as he felt for Hermione. Lucy is likewise given an inner conflict, as she is essentially engaged to Lord Haselby, an arranged match which she has already accepted.
After realizing he is in love with her, Gregory rushes to the church to stop Lucy's wedding to Haselby. Gregory arrives moments before the two exchange vows and confesses that he wants to marry Lucy. However, Lucy chooses to marry Haselby with a reason unknown to anyone but Lucy and her uncle.
After the wedding Gregory finds a way to speak with Lucy and eventually she tells him the truth. Lucy's uncle claims Haselby's father is blackmailing the family with proof that her deceased father was a traitor to England.
Now knowing the truth Gregory has to find a way to free Lucy from her marriage with Haselby. And it turns out it is the uncle who was the traitor.
Reception
The Romance Writers of America named On the Way to the Wedding the 2007 RITA Award winner for Best Long Historical Romance.[5] Romantic Times also nominated it for an award in 2006 in the category Historical Love & Laughter.[1]
Kathe Robin of Romantic Times gave a rave review of the novel, remarking that "Quinn deftly merges the elements of a Shakespearean comedy with the climax of The Graduate, delivering an utterly delightful love story that will have readers grinning with pleasure the instant the book is opened until the marvelous ending."[1] The review in Publishers' Weekly describes the novel as "as frothy and festive as a glass of bubbly, and more than worthy of a toast", but laments that the books does not include more interactions between the Bridgerton siblings, as previous books in the series had done.[3]
On the Way to the Wedding reached number 5 on the New York Times Bestseller List for paperback fiction.[6] The novel was on the USA Today bestseller list for six weeks, peaking at number
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Why Are Brides Choosing Micro Weddings
As COVID-19 impacts our daily lives and special occasions, micro weddings were born out of necessity. Between group gathering restrictions, social distancing guidelines, and travel bans, couples are now facing a new reality when planning their events. For some couples, this meant cutting down on their guest list, which in hindsight turned out to be more unexpected for others, Blessing indicated.
Obtaining a marriage license, hiring an officiant, and bringing along a few friends allows you to take advantage of smaller venues and hold your wedding in a place where a normal-sized wedding would never be possible. Fewer guests means less work, less budget, fewer opinions and pleasers, and more venue options for your celebration.
Micro weddings are intimate events that usually include 30 guests or fewer. While they tend to be less traditional, more and more couples are choosing to celebrate their dream wedding on a smaller scale. With the future being so uncertain, this is the best way to celebrate love if you don't want to wait or postpone your special day. What are the most common misconceptions?
For brides who have always dreamed of a big wedding, there is the fear that a "small" wedding isn't a "real" wedding. Many people feel scared or suffer regret when they have to cut back on everything, or think that all their efforts are for nothing if not everyone can participate. In fact, you are doing yourself, and maybe your family, a huge favor, because the constant back-and-forth is a big challenge for the bride and groom.
Tips To Ending A Situationship
Tell your situationship partner that you're ready to end things. Be clear, direct, honest, and kind by explaining that the situationship is no longer working for you: "I've enjoyed spending time with you but I think this has run its course. We want different things and it's not fair to either of us to keep doing this
Choose a calm, private setting to end things face to face.
If you have questions for your situationship partner or want some closure, having a face-to-face conversation is probably the best choice. Try to find a neutral spot where you can both be comfortable and where you won't have to worry about getting disrupted or fielding a lot of distractions. This signals that you're taking the conversation seriously.
If the two of you are more casual, you might not feel like this is necessary. When that's the case, a text is fine—just use your best judgment.
Saying something is usually the better than ghosting, though. Even though your relationship might have been undefined, that's no reason to leave the ending undefined as well.
Seek support if you need it.
Ending a situationship can hurt just as much as a regular breakup—the problem is you often don't have the support you need. You might have friends who didn't even know about the relationship, which can make it hard for them to understand how to comfort and support you now. Your most empathetic friends will support you emotionally, even if they don't quite understand how you feel or what your situationship partner meant to you.
Situationships often involve a lot of idealization. If you've caught feelings for your situationship partner, chances are you believed a "real" relationship between the two of you would be perfect, if only you could just get it off the ground.
During this time, remind yourself that your feelings are real and legitimate and you have every right to feel them. Acknowledge that you're grieving a loss, even if in this case it's more of a loss of what might've been. notes that one of the reasons "you can't get over it is because you kind of hoped it would turn into something more or at least something ongoing. And now that hope is over. So, it's just like, let it go and then go out and meet someone next."
The dynamic of your relationship doesn't matter—If your relationship partner is waving red flags, it's a good idea to head for the door. There's no reason to be in any kind of relationship with someone who treats you badly. If you can see red flags during a situationship, the person is not likely to act any differently if you do happen to end up in a committed relationship with them.
Why We Love Julia Quinn
Julia Pottinger (née Cotler; born January 12, 1970), better known by her pen name, Julia Quinn, is an American author of historical romance fiction.[1] Her novels have been translated into 41 languages and have appeared on The New York Times Bestseller List 19 times.[2] She has been inducted into the Romance Writers of America Hall of Fame. Her Bridgerton series of novels has been adapted for Netflix by Shondaland under the title Bridgerton.[3][4]
Quinn was born as Julie Cotler in 1970 to Jane and Stephen Lewis Cotler.[5] She has three sisters: Emily, Abigail, and Ariana.[6][7][8] She is Jewish.[9] She was raised primarily in New England, although she spent much of her time in California, following the divorce of her parents. [10]
Quinn developed an appreciation for literature at an early age, and since childhood, she thoroughly enjoyed reading. At age 12, her father disagreed with her choices of reading material, which included the Sweet Dreams and the Sweet Valley High book series, and he told her she could only continue reading them if she could prove that they contributed to the development of her reading skills. She promptly told him that she was studying the literary series, in order, because she was interested in writing a novel in the future. Challenged to prove that she was, indeed, interested in pursuing a writing career, Quinn sat down at their computer and wrote her first two chapters. After finishing her novel, three years
later, she submitted it to Sweet Dreams, but it was rejected.[11]
Quinn graduated from Hotchkiss School and Harvard University with a degree in Art History. During her senior year of college, she realized that she did not know what she wanted to do with her degree and decided to attend medical school. That decision required her to attend two additional years of college to complete the science prerequisites necessary to apply for medical school.[2] She postponed medical school for two years while she wrote two more novels.[11]
To occupy herself during the long days of studying science, Quinn began to write light-hearted Regency novels.[1] A few weeks after she was accepted to medical school, she discovered that her first two novels, Splendid and Dancing At Midnight, had been sold at auction, an unusual occurrence for a novice romance author.[12] By the time Quinn finally entered Yale School of Medicine, intending to become a doctor, three of her books had been published. After a few months of studying medicine, Quinn realized that she preferred writing to medical study. She left medical school and devoted herself, full-time, to her writing.
Quinn considers herself a feminist and gives her heroines feminist qualities that are not necessarily true to the most prevalent attitudes of the times her novels are set in.[1] Her books are noted for their humor and sharp, witty dialogue.[11] The novels are primarily character-driven, lacking the great external conflicts that many romance novels employ. One of her novels, When He Was Wicked, was unusual for a romance novel, as the first four chapters describe the heroine in a happy marriage with someone who is not the hero, and then shows the death of the original husband and deals with the grief of both the heroine and hero, before allowing the second love story to flourish.[12]
Most of her books are dedicated to her husband, Paul Pottinger, often with references to amusing alternate titles for the work. Quinn won the Romance Writers of America RITA Award, in 2007, for On the Way to the Wedding and again, in 2008, for The Secret Diaries of Miss Miranda Cheever. When she won, in 2010, for What Happens in London, she became (at the time) the youngest member and is now one of only 16 authors to be inducted into the RWA Hall of Fame.
In 2003, she enjoyed the rare honor of being profiled in Time Magazine, an accomplishment few romance novelists have achieved. In 2005, Publishers Weekly gave To Sir Phillip, With Love a rare starred review, and later, the novel was named as one of the six best mass market original novels of the year.[2]
Each of her last 17 novels have appeared on the New York Times Bestseller List, with Mr. Cavendish, I Presume hitting number one in October 2008. Most recently, The Girl With the Make-Believe Husband was on the NYT list in June 2017. In addition to those, both her Lady Whistledown anthologies appeared on the NY Times list, as did both of her novel-in-three-part collaborations with Connie Brockway and Eloisa James (The Lady Most Likely and The Lady Most Willing), and the Bridgertons: Happily Ever After collection of Bridgerton’s second epilogues.
Her Bridgerton series of books has been adapted for Netflix by Shonda Rhimes, under the title Bridgerton.[13][14]
Personal life
In 2001, Quinn won $79,000 on The Weakest Link.[15] She is an avid reader and posts recommendations of her favorite books on her Facebook page.
Quinn resides in Seattle, Washington,[16][17] with her husband and two children.[18][19][20]
On June 29, 2021, Quinn's sister and father, Ariana Elise Cotler and Stephen Lewis Cotler, respectively, were killed by a drunk driver in Kaysville, Utah
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Lather up with lukewarm water and rinse off your skin thoroughly. Makeup goes on best when your skin is clean and dry! Wash your face with lukewarm water and a gentle cleanser formulated for your skin type. Then, gently pat your face dry with a soft towel.
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If you have sensitive or acne-prone skin, stick with fragrance-free and non-comedogenic products.
Stick with a lightweight foundation if you want to even out your skin tone. Heavy and full-coverage foundations tend to look unnatural and can make you break out, so stay away from those Sheer/light coverage foundation, BB cream, and tinted moisturizer are all great options for a pretty, natural look.Use your fingers or a foundation brush to smooth a thin layer of product all over your face, starting in the center and blending out to your cheeks, forehead, and chin.
Choose a product that matches your skin tone so it blends naturally
Stick with liquid and cream formulas since they look more natural than powder foundations.
If you’re using your fingers, don't forget to wash your hands first, especially if you have acne-prone skin.
You could also consider using a face primer before your foundation as it will help the make up last longer.
A little concealer can disguise imperfections like pimples. Choose a concealer that matches your skin tone and use a fluffy eyeshadow brush to dab a small amount straight from the applicator on any dark spots or pimples you have. Then, buff around the spot lightly with a small makeup brush to blend the concealer out and you’re all set.
Use a fluffy brush to lightly dust your face with powder if you have oily skin. Go with a setting powder that matches your skin tone or use a translucent powder. Use a fluffy kabuki brush to dust a little powder all over your face. This locks in your foundation and gets rid of any shiny areas
Cream blush formulas are easy to blend and look really natural. Choose a rose or peachy shade and use your fingertips or a blush brush to smooth the blush on the apples of your cheeks. Use circular motions to blend the blush out toward your hairline for a soft, healthy-looking flush
Use a sheer rose or nude lip gloss for a hint of color. Hydrated lips look amazing on their own, so a little balm might be all you need to complete your look. To add a little shine, apply a clear or natural looking lip gloss. A natural-looking rose lip stain is a great way to add a little color.
Sleeping in your makeup can cause breakouts and clogged pores. Always remove your makeup at night before you hit the sack! Just soak a cotton round with oil-free makeup remover and rub it gently all over your face to get off most of your makeup. Then, follow up with a gentle cleanser to wash away any leftover residue and dirt.
For bigger eyes, put some shimmery, light colored shadow on the inner corners of your eyes. This opens your eyes up and makes you look more awake. Then, use a neutral color on your lid. At the outer corners of the eyes, use a darker color (like a plum or a chocolate brown). Apply it lightly. This gradient effect really opens up your eyes. Finish with a light application of brown or black eyeliner and some mascara.
Take a translucent pressed powder with you to mattify your face throughout the day. Definitely keep this with you if you have naturally oily skin, if have have a gym class, or live in a sunny area.
If you want to lightly contour your face use a cooler tone darker powder or bronzer to the hollows of your cheeks, hairline, and jaw line.
To make your lips look matte, put powder on top of a lip stick. This will make your lips look natural and not too glossy.
To make your application lighter, tap off any excess on your brush before you apply it on your face
Enhance Your Beauty Tips
Highlight your best features.
If you have amazing eyes, be sure to use mascara. If your teeth are white and wonderful, use a dark lipstick.
Make it look natural. Don't wear make-up for the sake of looking like you're wearing make-up. Wear it like its you're natural beauty! Better yet, go for the natural look if you want, and don't use it at all!
Find your style. This step practically goes without saying, but its surprising how many people forget what they look for in clothes and end up buying what's "in style."
Fit your figure. Not only do you need clothes you like, but you need clothes that like you. Look for clothes that fit to you and make you look good.
Smile. If you go around pouting everywhere you go, people will mark you as unhappy and not fun to be around. Smiling and being positive will make people happier to see you and improve what they think about you.
Keep good posture. Good posture shows confidence, and confidence has been described as the most attractive feature someone can posses. Keep your back straight and chin up, even when sitting. Keeping your back straight also helps flatten your stomach as fat then has a larger amount of space to be distributed over.
Wash your hair as often as necessary. Work with and enhance your hair's natural texture -- hot tools and blow dryers are damaging to your hair after repeated use.
Find good bottoms. The items that you wear on the bottom of your body, whether it's a skirt or slacks, also conform to a certain set of rules about what makes your body look best. As with all clothing items, the most important rule is to wear something that fits!
Flatter your bottom. Rule number one is definitely to wear pants that fit, no matter the size. If you want yours to look more shapely and you're a person of a lady-like persuasion, go for full shirts (either short or long). Either gender can go jeans with very structured and thick pockets, to create the illusion of shape. For those with a little too much bum, go for dark pants. Many of these same rules apply for flattering your hips.
Wear clothes that fit your height. Narrow, thin stripes will make you look taller, so avoid these if you're already towering over your peers. Wider stripes or horizontal stripes, however, will make you look shorter and fatter. Play with either stripe to achieve a look that works for you.
Get some tops. A few standard tops can be mixed and matched to work in any season, in any region. You can also mix and match for more or less formal occasions. This means just a few pieces will get you through almost any given day!
Get a few basic tees and tanks. Get tee shirts and tank tops (or other warm-weather shirts) that look good on you. You'll want some in neutral colors and some in more interesting colors.
Get some fancy tops. You'll then want to get some fancier shirts. These are the kinds of shirts that you might wear to a nice bar or a cocktail party. Choose these in sensual or dark colors.
Get some basic button-downs. You'll want several pairs of basic button-down shirts. Depending on the weather in your area, these can be long or short sleeve or a mix of the two. Have most in white, but a few can be colored or black.
Get some sweaters. Now you'll want some sweaters. How heavy-duty these are and how many you get will depend on the weather in your area. Have at least one cardigan (button-down sweater) and one full sweater. More than one of each is a good idea so that you can have one of each in a neutral color and one of each in a brighter color.
Get some dresses. If you're a guy, just get one suit that fits you well. Girls, however, will probably want a couple of dresses for certain occasions.
Get a formal dress. One formal dress, usually a nice cocktail dress in black, will be useful for semi-formal events. With the right jewelry and the right dress, it may even be able to pass for more formal situations, depending on the particulars.
Get a day dress. Now get a dress that is more casual but still pretty. This one will be used for both nice summer days and events like weddings and garden parties.
Get a short dress. If you want to, you can get a short dress. This can be worn over jeans or leggings for a cute look to go to the mall, or it can be worn on its own to go clubbing.
Get some accessories. Accessories are a great area to let your personality shine through. You can get sunglasses, scarves, hats, purses, watches, and other items that show who you are.
# NeoLife: Contributions to Health Management and Disease Prevention
NeoLife is a renowned global health and wellness company that emphasizes superior nutrition and scientific innovation. Founded in 1958, NeoLife offers a comprehensive range of nutritional supplements, weight management products, and personal care items designed to enhance overall health. This extensive guide explores how NeoLife products can aid in managing upper respiratory infections, high blood pressure, diabetes, and other infections, as well as the benefits of their specialized product, PhytoDefense.
## Upper Respiratory Infections
### Understanding Upper Respiratory Infections
Upper respiratory infections (URIs) include common colds, sinusitis, pharyngitis, and laryngitis. They are typically caused by viruses but can also be bacterial. Symptoms include a runny nose, sore throat, cough, congestion, and fatigue.
### NeoLife’s Approach to Managing Upper Respiratory Infections
Managing URIs involves boosting the immune system, reducing inflammation, and maintaining overall health. NeoLife offers various products that can support these objectives:
#### Immune System Support
A robust immune system is crucial for preventing and managing URIs. NeoLife provides several supplements that enhance immune function:
- **Vitamin C Sustained Release**: This product provides a steady release of vitamin C, an essential antioxidant that supports the immune system and helps the body fight infections.
- **All-C**: A chewable vitamin C supplement offering antioxidant protection and immune support.
- **Garlic Allium Complex**: Contains garlic and other allium vegetables known for their immune-boosting and antimicrobial properties.
- **Zinc**: An essential mineral that supports immune function and aids in recovery from infections.
#### Reducing Inflammation
Inflammation is a key factor in the symptoms and severity of URIs. NeoLife’s products rich in omega-3 fatty acids and other anti-inflammatory compounds can help:
- **Omega-3 Salmon Oil Plus**: Provides a rich source of omega-3 fatty acids, including EPA and DHA, which have anti-inflammatory properties and support overall health.
#### Overall Health and Wellness
Maintaining overall health through balanced nutrition and essential nutrients can help prevent and manage URIs:
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals.
## High Blood Pressure
### Understanding High Blood Pressure
High blood pressure, or hypertension, is a chronic condition characterized by elevated blood pressure levels, increasing the risk of heart disease, stroke, and kidney disease. Risk factors include poor diet, lack of physical activity, obesity, and genetics.
### NeoLife’s Approach to Managing High Blood Pressure
Managing high blood pressure involves a combination of lifestyle changes, dietary modifications, and nutritional support. NeoLife offers several products that can aid in managing hypertension:
#### Supporting Cardiovascular Health
NeoLife’s products are designed to support cardiovascular health and help manage blood pressure:
- **Omega-3 Salmon Oil Plus**: Omega-3 fatty acids are known to support heart health by reducing inflammation, lowering blood pressure, and improving lipid profiles.
- **Lipotropic Adjunct**: Helps maintain healthy cholesterol levels and supports liver function, which is crucial for cardiovascular health.
- **Garlic Allium Complex**: Garlic has been shown to help lower blood pressure and improve overall heart health.
#### Reducing Inflammation and Oxidative Stress
Chronic inflammation and oxidative stress are significant contributors to hypertension. NeoLife’s antioxidant-rich products can help mitigate these factors:
- **Carotenoid Complex**: Contains a blend of carotenoids, such as beta-carotene, lycopene, and lutein, derived from fruits and vegetables. Carotenoids have been shown to protect cells from oxidative damage and support heart health.
- **Flavonoid Complex**: Rich in flavonoids from a variety of fruits and vegetables, this product provides powerful antioxidant protection and supports cardiovascular health.
#### Promoting Overall Health
Maintaining overall health through balanced nutrition is essential for managing high blood pressure:
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants.
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
## Diabetes
### Understanding Diabetes
Diabetes is a chronic condition characterized by elevated blood glucose levels due to either insufficient insulin production (Type 1 diabetes) or insulin resistance (Type 2 diabetes). Managing diabetes involves maintaining healthy blood glucose levels through diet, exercise, and medication.
### NeoLife’s Approach to Managing Diabetes
Managing diabetes requires a multifaceted approach, including nutritional support. NeoLife offers several products that can help manage blood glucose levels and support overall health:
#### Blood Sugar Control
NeoLife provides supplements that can aid in regulating blood sugar levels:
- **Glucose Balance**: Contains a blend of ingredients like chromium, which supports healthy blood sugar levels and helps maintain insulin sensitivity.
- **Omega-3 Salmon Oil Plus**: Omega-3 fatty acids help reduce inflammation and support overall metabolic health, which is beneficial for managing diabetes.
#### Supporting Metabolic Health
Maintaining metabolic health is crucial for managing diabetes. NeoLife’s products can support metabolic function and overall well-being:
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals.
#### Reducing Inflammation and Oxidative Stress
Chronic inflammation and oxidative stress are significant factors in the development and progression of diabetes. NeoLife’s antioxidant-rich products can help mitigate these factors:
- **Carotenoid Complex**: Contains a blend of carotenoids, such as beta-carotene, lycopene, and lutein, derived from fruits and vegetables. Carotenoids have been shown to protect cells from oxidative damage.
- **Flavonoid Complex**: Rich in flavonoids from a variety of fruits and vegetables, this product provides powerful antioxidant protection and supports overall health.
## Other Infections
### Understanding Other Infections
Infections can be caused by various pathogens, including bacteria, viruses, fungi, and parasites. The body’s immune system plays a crucial role in defending against infections, and maintaining optimal health is essential for robust immune function.
### NeoLife’s Approach to Managing Other Infections
Preventing and managing infections involve supporting the immune system, reducing inflammation, and maintaining overall health. NeoLife offers several products that can aid in these objectives:
#### Immune System Support
A robust immune system is crucial for preventing and managing infections. NeoLife provides several supplements that enhance immune function:
- **Vitamin C Sustained Release**: Provides a steady release of vitamin C, an essential antioxidant that supports the immune system and helps the body fight infections.
- **All-C**: A chewable vitamin C supplement offering antioxidant protection and immune support.
- **Garlic Allium Complex**: Contains garlic and other allium vegetables known for their immune-boosting and antimicrobial properties.
- **Zinc**: An essential mineral that supports immune function and aids in recovery from infections.
#### Reducing Inflammation
Inflammation is a key factor in the symptoms and severity of infections. NeoLife’s products rich in omega-3 fatty acids and other anti-inflammatory compounds can help:
- **Omega-3 Salmon Oil Plus**: Provides a rich source of omega-3 fatty acids, including EPA and DHA, which have anti-inflammatory properties and support overall health.
#### Overall Health and Wellness
Maintaining overall health through balanced nutrition and essential nutrients can help prevent and manage infections:
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals.
## PhytoDefense: A Specialized NeoLife Product
### Understanding PhytoDefense
PhytoDefense is one of NeoLife’s specialized products designed to provide comprehensive antioxidant protection and support overall health. It contains a blend of powerful phytonutrients derived from fruits, vegetables, and other plant sources.
### Components of PhytoDefense
PhytoDefense includes three key components:
1. **Carotenoid Complex**: Contains a blend of carotenoids, such as beta-carotene, lycopene, and lutein, derived from fruits and vegetables. Carotenoids are potent antioxidants that protect cells from oxidative damage and support immune function.
2. **Flavonoid Complex**: Rich in flavonoids from a variety of fruits and vegetables, this component provides powerful antioxidant protection and supports cardiovascular health.
3. **Cruciferous Plus**: Contains extracts from cruciferous vegetables like broccoli, kale, and Brussels sprouts. These vegetables are known for their cancer-protective properties and overall health benefits.
### Benefits of PhytoDefense
PhytoDefense offers several health benefits due to its rich blend of phytonutrients:
#### Antioxidant Protection
PhytoDefense provides comprehensive antioxidant protection, which helps neutralize free radicals and reduce oxidative stress. This protection is crucial for preventing chronic diseases and supporting overall health
# NeoLife and the Role of Nutritional Support in Managing Infectious Diseases
NeoLife, a global health and wellness company, is renowned for its commitment to superior nutrition and scientific innovation. Since its founding in 1958, NeoLife has offered a range of nutritional supplements, weight management products, and personal care items designed to enhance overall health. This comprehensive guide explores how NeoLife products can support the management and prevention of various infectious diseases by boosting the immune system, reducing inflammation, and promoting overall wellness.
## Infectious Diseases and the Immune System
Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites, and fungi. These diseases can spread directly or indirectly from one person to another. The immune system plays a critical role in defending against these pathogens. When functioning optimally, it can identify and destroy harmful invaders, preventing illness and aiding recovery.
### Importance of Nutrition in Immune Function
Nutrition is fundamental to maintaining a strong immune system. Certain nutrients and bioactive compounds can enhance immune responses, reduce inflammation, and improve overall health. NeoLife’s products are formulated to provide these essential nutrients, supporting the body's natural defenses against infectious diseases.
## Upper Respiratory Infections
### Understanding Upper Respiratory Infections
Upper respiratory infections (URIs) include common illnesses such as the common cold, sinusitis, pharyngitis, and laryngitis. They are primarily caused by viruses, although bacterial infections can also occur. Symptoms typically include a runny nose, sore throat, cough, congestion, and fatigue.
### NeoLife’s Approach to Managing Upper Respiratory Infections
NeoLife offers a range of products that can support the management of URIs by enhancing immune function, reducing inflammation, and promoting overall wellness.
#### Immune System Support
A robust immune system is essential for preventing and managing URIs. NeoLife provides several supplements that boost immune function:
- **Vitamin C Sustained Release**: This product provides a steady release of vitamin C, an essential antioxidant that supports the immune system and helps the body fight infections.
- **All-C**: A chewable vitamin C supplement offering antioxidant protection and immune support.
- **Garlic Allium Complex**: Contains garlic and other allium vegetables known for their immune-boosting and antimicrobial properties.
- **Zinc**: An essential mineral that supports immune function and aids in recovery from infections.
#### Reducing Inflammation
Inflammation is a key factor in the symptoms and severity of URIs. NeoLife’s products rich in omega-3 fatty acids and other anti-inflammatory compounds can help:
- **Omega-3 Salmon Oil Plus**: Provides a rich source of omega-3 fatty acids, including EPA and DHA, which have anti-inflammatory properties and support overall health.
#### Overall Health and Wellness
Maintaining overall health through balanced nutrition and essential nutrients can help prevent and manage URIs:
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals.
## Lower Respiratory Infections
### Understanding Lower Respiratory Infections
Lower respiratory infections (LRIs) include pneumonia, bronchitis, and tuberculosis. These infections affect the airways and lungs and can be caused by bacteria, viruses, or fungi. Symptoms often include cough, chest pain, difficulty breathing, and fever.
### NeoLife’s Approach to Managing Lower Respiratory Infections
NeoLife’s products can support the management of LRIs by enhancing immune function, reducing inflammation, and promoting overall health.
#### Immune System Support
Boosting the immune system is crucial for preventing and managing LRIs. NeoLife offers several supplements that enhance immune function:
- **Vitamin C Sustained Release**: Provides a steady release of vitamin C, which supports the immune system and helps the body fight infections.
- **All-C**: A chewable vitamin C supplement offering antioxidant protection and immune support.
- **Garlic Allium Complex**: Contains garlic and other allium vegetables known for their immune-boosting and antimicrobial properties.
- **Zinc**: An essential mineral that supports immune function and aids in recovery from infections.
#### Reducing Inflammation
Inflammation plays a significant role in the symptoms and severity of LRIs. NeoLife’s products rich in omega-3 fatty acids and other anti-inflammatory compounds can help:
- **Omega-3 Salmon Oil Plus**: Provides a rich source of omega-3 fatty acids, including EPA and DHA, which have anti-inflammatory properties and support overall health.
#### Supporting Respiratory Health
Maintaining respiratory health is crucial for managing LRIs. NeoLife’s products can support lung function and overall respiratory health:
- **Resp-X**: A blend of herbs known to support respiratory health and relieve symptoms of respiratory infections.
- **Aloe Vera Plus**: A soothing drink that supports digestive health and overall wellness, which can indirectly benefit respiratory health.
## Gastrointestinal Infections
### Understanding Gastrointestinal Infections
Gastrointestinal (GI) infections affect the stomach and intestines and are caused by bacteria, viruses, or parasites. Common GI infections include gastroenteritis, food poisoning, and infections by *Helicobacter pylori*. Symptoms often include diarrhea, vomiting, stomach cramps, and fever.
### NeoLife’s Approach to Managing Gastrointestinal Infections
NeoLife’s products can support the management of GI infections by enhancing immune function, supporting digestive health, and promoting overall wellness.
#### Immune System Support
A strong immune system is essential for preventing and managing GI infections. NeoLife provides several supplements that boost immune function:
- **Vitamin C Sustained Release**: Provides a steady release of vitamin C, which supports the immune system and helps the body fight infections.
- **All-C**: A chewable vitamin C supplement offering antioxidant protection and immune support.
- **Garlic Allium Complex**: Contains garlic and other allium vegetables known for their immune-boosting and antimicrobial properties.
- **Zinc**: An essential mineral that supports immune function and aids in recovery from infections.
#### Supporting Digestive Health
Maintaining digestive health is crucial for managing GI infections. NeoLife’s products can support gut function and overall digestive health:
- **Acidophilus Plus**: A probiotic supplement that helps maintain a healthy balance of gut bacteria, which is essential for digestive health and immune function.
- **Fibre Tablets**: Provide dietary fiber that supports digestive health and regular bowel movements.
- **Aloe Vera Plus**: A soothing drink that supports digestive health and overall wellness.
#### Overall Health and Wellness
Maintaining overall health through balanced nutrition and essential nutrients can help prevent and manage GI infections:
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals.
## Urinary Tract Infections
### Understanding Urinary Tract Infections
Urinary tract infections (UTIs) are common infections that affect the urinary system, including the bladder, urethra, and kidneys. They are typically caused by bacteria, with *Escherichia coli* being the most common pathogen. Symptoms include a strong, persistent urge to urinate, a burning sensation when urinating, and cloudy or strong-smelling urine.
### NeoLife’s Approach to Managing Urinary Tract Infections
NeoLife’s products can support the management of UTIs by enhancing immune function, reducing inflammation, and promoting overall wellness.
#### Immune System Support
A robust immune system is essential for preventing and managing UTIs. NeoLife provides several supplements that boost immune function:
- **Vitamin C Sustained Release**: Provides a steady release of vitamin C, which supports the immune system and helps the body fight infections.
- **All-C**: A chewable vitamin C supplement offering antioxidant protection and immune support.
- **Garlic Allium Complex**: Contains garlic and other allium vegetables known for their immune-boosting and antimicrobial properties.
- **Zinc**: An essential mineral that supports immune function and aids in recovery from infections.
#### Supporting Urinary Health
Maintaining urinary health is crucial for managing UTIs. NeoLife’s products can support bladder function and overall urinary health:
- **Cranberry Plus**: Contains cranberry extract, which is known to support urinary health and prevent bacterial adhesion to the bladder wall.
- **Aloe Vera Plus**: A soothing drink that supports digestive health and overall wellness, which can indirectly benefit urinary health.
#### Reducing Inflammation
Inflammation plays a significant role in the symptoms and severity of UTIs. NeoLife’s products rich in omega-3 fatty acids and other anti-inflammatory compounds can help:
- **Omega-3 Salmon Oil Plus**: Provides a rich source of omega-3 fatty acids, including EPA and DHA, which have anti-inflammatory properties and support overall health.
#### Overall Health and Wellness
Maintaining overall health through balanced nutrition and essential nutrients can help prevent and manage UTIs:
- **Pro Vitality**: A daily supplement pack that includes essential nutrients like vitamins, minerals, omega-3 fatty acids, and antioxidants.
- **Tre-en-en Grain Concentrates**: This supplement provides essential lipids and sterols from whole grains, which help maintain cell membrane integrity and support nutrient absorption.
- **NeoLifeShake**: A nutrient-dense meal replacement shake that provides balanced protein, vitamins, and minerals.
## Skin Infections
### Understanding Skin Infections
Skin infections can be caused by bacteria, viruses, fungi, or
Multi-level marketing (MLM), also called network marketing[1] or pyramid selling,[2][3][4] is a controversial[5] marketing strategy for the sale of products or services in which the revenue of the MLM company is derived from a non-salaried workforce selling the company's products or services, while the earnings of the participants are derived from a pyramid-shaped or binary compensation commission system.[6]
In multi-level marketing, the compensation plan usually pays out to participants from two potential revenue streams. The first is based on a sales commission from directly selling the product or service; the second is paid out from commissions based upon the wholesale purchases made by other sellers whom the participant has recruited to also sell product. In the organizational hierarchy of MLM companies, recruited participants (as well as those whom the recruit recruits) are referred to as one's downline distributors.[7]
MLM salespeople are, therefore, expected to sell products directly to end-user retail consumers by means of relationship referrals and word of mouth marketing, but more importantly they are incentivized to recruit others to join the company's distribution chain as fellow salespeople so that these can become downline distributors.[1][8] According to a report that studied the business models of 350 MLM companies in the United States, published on the Federal Trade Commission's website, at least 99% of people who join MLM companies lose money.[9][10][11] Nonetheless, MLM companies function because downline participants are encouraged to hold onto the belief that they can achieve large returns, while the statistical improbability of this is de-emphasized. MLM companies have been made illegal or otherwise strictly regulated in some jurisdictions as merely variations of the traditional pyramid scheme.[12][13]
Terminology
Multi-level marketing is also known as "pyramid selling",[2][3] "network marketing",[3][1] and "referral marketing".[14]
Business model
Setup
A typical multi-level marketing binary tree structure. The blue individual at the top will receive compensation from the sales of the downline red members.
Independent non-salaried participants, referred to as distributors (variously called "associates", "independent business owners", "independent agents", "affiliates", etc.), are authorized to distribute the company's products or services. They are awarded their own immediate retail profit from customers plus commission from the company, not downlines, through a multi-level marketing compensation plan, which is based upon the volume of products sold through their own sales efforts as well as that of their downline organization.
Independent distributors develop their organizations by either building an active consumer network, who buy direct from the company, or by recruiting a downline of independent distributors who also build a consumer network base, thereby expanding the overall organization.[citation needed]
The combined number of recruits from these cycles are the sales force which is referred to as the salesperson's "downline". This "downline" is the pyramid in MLM's multiple-level structure of compensation.[8]
Participants
The overwhelming majority of MLM participants participate at either an insignificant or nil net profit. A study of 27 MLM schemes found that on average, 99.6% of participants lost money.[15] Indeed, the largest proportion of participants must operate at a net loss (after expenses are deducted) so that the few individuals in the uppermost level of the MLM pyramid can derive their significant earnings. Said earnings are then emphasized by the MLM company to all other participants to encourage their continued participation at a continuing financial loss.[15]
Companies
Many MLM companies generate billions of dollars in annual revenue and hundreds of millions of dollars in annual profit. However, profits accrue to the detriment of the majority of the company's constituent workforce (the MLM participants). Only some of the profits are then shared with individual participants at the top of the MLM distributorship pyramid. The earnings of those top few participants are emphasized and championed at company seminars and conferences, thus creating the illusion that participants in the MLM can become financially successful. This is then advertised by the MLM company to recruit more distributors in the MLM with an unrealistic anticipation of earning margins which are in reality merely theoretical and statistically improbable.[16]
Although an MLM company holds out those few top individual participants as evidence of how participation in the MLM could lead to success, the MLM business model depends on the failure of the overwhelming majority of all other participants, through the injecting of money from their own pockets, so that it can become the revenue and profit of the MLM company, of which the MLM company shares only a small proportion with a few individuals at the top of the MLM participant pyramid. Other than the few at the top, participants provide nothing more than their own financial loss for the company's own profit and the profit of the top few individual participants.[17]
Financial independence
The main sales pitch of MLM companies to their participants and prospective participants is not the MLM company's products or services. The products or services are largely peripheral to the MLM model. [citation needed] Rather, the true sales pitch and emphasis is on a confidence given to participants of potential financial independence through participation in the MLM, luring with phrases like "the lifestyle you deserve" or "independent distributor".[18] Erik German's memoir My Father's Dream documents the author's father's failures through "get-rich-quick schemes" such as Amway.[19] The memoir illustrates the multi-level marketing sales principle known as "selling the dream".[20]
Although the emphasis is always made on the potential of success and the positive life change that "might" or "could" (not "will" or "can") result, disclosure statements include disclaimers that they, as participants, should not rely on the earning results of other participants in the highest levels of the MLM participant pyramid as an indication of what they should expect to earn. MLM companies rarely emphasize the extreme likelihood of failure, or the extreme likelihood of financial loss, from participation in MLM. [citation needed]
Comparisons to pyramid schemes
MLM companies have been made illegal in some jurisdictions as a mere variation of the traditional pyramid scheme, including in China.[12][13] In jurisdictions where MLM companies have not been made illegal, many illegal pyramid schemes attempt to present themselves as MLM businesses.[21] Given that the overwhelming majority of MLM participants cannot realistically make a net profit, let alone a significant net profit, but instead overwhelmingly operate at net losses, some sources have defined all MLM companies as a type of pyramid scheme, even if they have not been made illegal like traditional pyramid schemes through legislative statutes.[14][22][23]
MLM companies are designed to make profit for the owners/shareholders of the company and a few individual participants at the top levels of the MLM pyramid of participants. According to the U.S. Federal Trade Commission (FTC), some MLM companies already constitute illegal pyramid schemes even by the narrower existing legislation, exploiting members of the organization.[24]
Lawsuits
This section is in list format but may read better as prose. You can help by converting this section, if appropriate. Editing help is available. (December 2021)
Companies that use the MLM business model have been a frequent subject of criticism and lawsuits. Legal claims against MLM companies have included the following, among other things:
Their similarity to traditional illegal pyramid schemes
Price fixing of products or services
Collusion and racketeering in backroom deals where secret compensation packages are created between the MLM company and a few individual participants, to the detriment of others
High initial entry costs (for marketing kit and first products)
Emphasis on recruitment of others over actual sales (especially sales to non-participants)
Encouraging if not requiring members to purchase and use the company's products
Exploitation of personal relationships as both sales and recruiting targets
Complex and exaggerated compensation schemes
False product claims
The company or leading distributors making major money off participant-attended conventions, training events and materials, and advertising materials
Cult-like techniques, which some groups use to enhance their members' enthusiasm and devotion[14][25]
Direct selling versus network marketing
"Network marketing" and "multi-level marketing" (MLM) have been described by author Dominique Xardel as being synonymous, with it being a type of direct selling.[8] Some sources emphasize that multi-level marketing is merely one form of direct selling, rather than being direct selling.[26][27] Other terms that are sometimes used to describe multi-level marketing include "word-of-mouth marketing", "interactive distribution", and "relationship marketing". Critics have argued that the use of these and other different terms and "buzzwords" is an effort to draw distinctions between multi-level marketing and illegal Ponzi schemes, chain letters, and consumer fraud scams—where none meaningfully exist.[28]
The Direct Selling Association (DSA), a lobbying group for the MLM industry, reported that in 1990 only 25% of DSA members used the MLM business model. By 1999, this had grown to 77.3%.[29] By 2009, 94.2% of DSA members were using MLM, accounting for 99.6% of sellers, and 97.1% of sales.[30] Companies such as Avon, Electrolux, Tupperware, and Kirby were all originally single-level marketing companies, using that traditional and uncontroversial direct selling business model (distinct from MLM) to sell their goods. However, they later introduced multi-level compensation plans, becoming MLM companies.[26] The DSA has approximately 200 members[31] while it is estimated there are over 1,000 firms using multi-level marketing in the United States alone.[32]
History
[icon]
This section needs expansion. You can help by adding to it. (June 2020)
The origin of multi-level marketing is often disputed, but multi-level marketing style businesses existed in the 1920s[33] and the 1930s, such as the California Vitamin Company[34] (later named Nutrilite) and the California Perfume Company (renamed "Avon Products").[35]
Income levels
This section is in list format but may read better as prose. You can help by converting this section, if appropriate. Editing help is available. (April 2021)
Several sources have commented on the income level of specific MLM companies or MLM companies in general:
The Times: "The Government investigation claims to have revealed that just 10% of Amway's agents in Britain make any profit, with less than one in ten selling a single item of the group's products."[36]
Eric Scheibeler, a high level "Emerald" Amway member: "UK Justice Norris found in 2008 that out of an IBO [Independent Business Owners] population of 33,000, 'only about 90 made sufficient incomes to cover the costs of actively building their business.' That's a 99.7 percent loss rate for investors."[37]
Newsweek: based on Mona Vie's own 2007 income disclosure statement "fewer than 1 percent qualified for commissions and of those, only 10 percent made more than $100 a week."[38]
Business Students Focus on Ethics: "In the USA, the average annual income from MLM for 90% MLM members is no more than US $5,000, which is far from being a sufficient means of making a living (San Lian Life Weekly 1998)"[39]
USA Today has had several articles:
"While earning potential varies by company and sales ability, DSA says the median annual income for those in direct sales is $2,400."[40]
In an October 15, 2010, article, it was stated that documents of a MLM called Fortune Hi-Tech Marketing reveal that 30 percent of its representatives make no money and that 54 percent of the remaining 70 percent only make $93 a month, before costs. Fortune was under investigation by the Attorneys General of Texas, Kentucky, North Dakota, and North Carolina with Missouri, South Carolina, Illinois, and Florida following up complaints against the company.[41] The FTC eventually stated that Fortune Hi-Tech Marketing was a pyramid scheme and that checks totaling more than $3.7 million were being mailed to the victims.[42]
A February 10, 2011, article stated "It can be very difficult, if not impossible, for most individuals to make a lot of money through the direct sale of products to consumers. And big money is what recruiters often allude to in their pitches."[43]
"Roland Whitsell, a former business professor who spent 40 years researching and teaching the pitfalls of multilevel marketing": "You'd be hard-pressed to find anyone making over $1.50 an hour, (t)he primary product is opportunity. The strongest, most powerful motivational force today is false hope."[43]
Based on the results of a 2018 poll conducted with 1,049 MLM sellers, the majority (60%) earned an average of less than $100 in sales over a five-year period, and 20% never made a single sale. The majority of sellers made less than 70 cents per hour.[44] Nearly 32 percent of those polled acquired credit card debt to finance their MLM involvement.[45]
Legality and legitimacy
Bangladesh
In 2015, the Government of Bangladesh banned all types of domestic and foreign MLM trade in Bangladesh.[46]
China
Multi-level marketing (simplified Chinese: 传销; traditional Chinese: 傳銷; pinyin: chuán xiāo; lit. 'spread selling') was first introduced to mainland China by American, Taiwanese, and Japanese companies following the Chinese economic reform of 1978. This rise in multi-level marketing's popularity coincided with economic uncertainty and a new shift towards individual consumerism. Multi-level marketing was banned on the mainland by the government in 1998, citing social, economic, and taxation issues.[47] Further regulation "Prohibition of Chuanxiao" (where MLM is a type of Chuanxiao was enacted in 2005, clause 3 of Chapter 2 of the regulation states having downlines is illegal).[13] O'Regan wrote 'With this regulation China makes clear that while Direct Sales is permitted in the mainland, Multi-Level Marketing is not'.[12]
MLM companies have been made illegal in China as a mere variation of the traditional pyramid scheme and as disruptive to social and economic order.[12][48] MLM companies have been trying to find ways around China's prohibitions, or have been developing other methods, such as direct sales, to take their products to China through retail operations. The Direct Sales Regulations limit direct selling to cosmetics, health food, sanitary products, bodybuilding equipment and kitchen utensils, and they require Chinese or foreign companies ("FIEs") who intend to engage into direct sale business in mainland China to apply for and obtain direct selling license from the Ministry of Commerce ("MOFCOM").[49] In 2016, there are 73 companies, including domestic and foreign companies, that have obtained the direct selling license.[50] Some multi-level marketing sellers have circumvented this ban by establishing addresses and bank accounts in Hong Kong, where the practice is legal, while selling and recruiting on the mainland.[12][51]
It was not until August 23, 2005, that the State Council promulgated rules that dealt specifically with direct sale operation- Administration of Direct Sales (entered into effect on December 1, 2005) and the Regulations for the Prohibition of Chuanxiao (entered into effect on November 1, 2005). When direct selling is allowed, it will only be permitted under the most stringent requirements, in order to ensure the operations are not pyramid schemes, MLM, or fly-by-night operations.
Saudi Arabia
MLM marketing is banned in Saudi Arabia by imposing religious fatwa nationally, for this reason MLM companies like Amway, Mary Kay, Oriflame and Herbalife sell their products by online selling method instead of MLM.[52]
United States
MLM businesses operate in all 50 U.S. states. Businesses may use terms such as "affiliate marketing" or "home-based business franchising". Some sources say that all MLM companies are essentially pyramid schemes, even if they are legal.[14][22][23] Utah has been named the "unofficial world capital of multi-level marketing and direct sales companies" and is home to at least 15 major MLMs, more MLMs per capita than any other state.[53]
The U.S. Federal Trade Commission (FTC) states: "Steer clear of multilevel marketing plans that pay commissions for recruiting new distributors. They're actually illegal pyramid schemes. Why is pyramiding dangerous? Because plans that pay commissions for recruiting new distributors inevitably collapse when no new distributors can be recruited. And when a plan collapses, most people—except perhaps those at the very top of the pyramid—end up empty-handed."[54]
In a 2004 Staff Advisory letter to the Direct Selling Association, the FTC states:
Much has been made of the personal, or internal, consumption issue in recent years. In fact, the amount of internal consumption in any multi-level compensation business does not determine whether or not the FTC will consider the plan a pyramid scheme. The critical question for the FTC is whether the revenues that primarily support the commissions paid to all participants are generated from purchases of goods and services that are not simply incidental to the purchase of the right to participate in a money-making venture.[55]
The Federal Trade Commission warns
Not all multilevel marketing plans are legitimate. Some are pyramid schemes. It's best not to get involved in plans where the money you make is based primarily on the number of distributors you recruit and your sales to them, rather than on your sales to people outside the plan who intend to use the products.[24]
In re Amway Corp. (1979), the Federal Trade Commission indicated that multi-level marketing was not illegal per se in the United States. However, Amway was found guilty of price fixing (by effectively requiring "independent" distributors to sell at the same fixed price) and making exaggerated income claims.[56][57] The FTC advises that multi-level marketing organizations with greater incentives for recruitment than product sales are to be viewed skeptically. The FTC also warns that the practice of getting commissions from recruiting new members is outlawed in most states as "pyramiding".[58]
Walter J. Carl stated in a 2004 Western Journal of Communication article that "MLM organizations have been described by some as cults (Butterfield, 1985),[59] pyramid schemes (Fitzpatrick & Reynolds, 1997),[60] or organizations rife with misleading, deceptive, and unethical behavior (Carter, 1999),[61] such as the questionable use of evangelical discourse to promote the business (Höpfl & Maddrell, 1996),[62] and the exploitation of personal relationships for financial gain (Fitzpatrick & Reynolds, 1997)".[60][63] In China, volunteers working to rescue people from the schemes have been physically attacked.[64]
MLM companies are also criticized for being unable to fulfill their promises for the majority of participants due to basic conflicts with Western cultural norms.[65] There are even claims that the success rate for breaking even or even making money are far worse than other types of businesses:[66] "The vast majority of MLM companies are recruiting MLM companies, in which participants must recruit aggressively to profit. Based on available data from the companies themselves, the loss rate for recruiting MLM companies is approximately 99.9%; i.e., 99.9% of participants lose money after subtracting all expenses, including purchases from the company."[66] (By comparison, skeptic Brian Dunning points out that "only 97.14% of Las Vegas gamblers lose money .... ."[67]) In part, this is because encouraging recruits to further "recruit people to compete with [them]"[14] leads to "market saturation."[25] It has also been claimed "(b)y its very nature, MLM is completely devoid of any scientific foundations."[68]
Because of the encouraging of recruits to further recruit their competitors, some people have even gone so far as to say at best modern MLM companies are nothing more than legalized pyramid schemes[14][22][23] with one stating "Multi-level marketing companies have become an accepted and legally sanctioned form of pyramid scheme in the United States"[22] while another states "Multi-Level Marketing, a form of Pyramid Scheme, is not necessarily fraudulent."[23] In October 2010 it was reported that multi-level marketing companies were being investigated by a number of state attorneys general amid allegations that salespeople were primarily paid for recruiting and that more recent recruits cannot earn anything near what early entrants do.[69] Industry critic Robert L. FitzPatrick has called multi-level marketing "the Main Street bubble" that will eventually burst.[70]
Religious views
Islam
Many Islamic jurists and religious bodies, including Permanent Committee for Scholarly Research and Ifta[71] of Saudi Arabia, have considered MLM trade to be prohibited (haram). They argue that MLM trade involves deceiving others into participating, and the transaction bears resemblance to both riba and gharar.[72][73]
mma-butyrobetaine dioxygenase (also known as BBOX, GBBH or γ-butyrobetaine hydroxylase) is an enzyme that in humans is encoded by the BBOX1 gene.[5][6] Gamma-butyrobetaine dioxygenase catalyses the formation of L-carnitine from gamma-butyrobetaine, the last step in the L-carnitine biosynthesis pathway.[7] Carnitine is essential for the transport of activated fatty acids across the mitochondrial membrane during mitochondrial beta oxidation.[6] In humans, gamma-butyrobetaine dioxygenase can be found in the kidney (high), liver (moderate), and brain (very low).[5][8] BBOX1 has recently been identified as a potential cancer gene based on a large-scale microarray data analysis.[9]
Reaction
gamma-butyrobetaine dioxygenase
Identifiers
EC no. 1.14.11.1
CAS no. 9045-31-2
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO
Search
Gamma-butyrobetaine dioxygenase belongs to the 2-oxoglutarate (2OG)-dependent dioxygenase superfamily. It catalyses the following reaction:
4-trimethylammoniobutanoate (γ-butyrobetaine) + 2-oxoglutarate + O2
⇌{\displaystyle \rightleftharpoons } 3-hydroxy-4-trimethylammoniobutanoate (L-carnitine) + succinate + CO2
The three substrates of this enzyme are 4-trimethylammoniobutanoate (γ-butyrobetaine), 2-oxoglutarate, and O2,[10] whereas its three products are 3-hydroxy-4-trimethylammoniobutanoate (L-carnitine), succinate, and carbon dioxide.
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with 2-oxoglutarate as one donor, and incorporation of one atom of oxygen into each donor. This enzyme participates in lysine degradation. Iron is a cofactor for gamma-butyrobetaine dioxygenase. Similar to many other 2OG oxygenases, the activity of gamma-butyrobetaine dioxygenase can be stimulated by reducing agents such as ascorbate and glutathione.[11][12][13][14] The catalytic activity of gamma-butyrobetaine dioxygenase can be stimulated with different metal ions, especially potassium ions.[15]
Both the apo (PDB id: 3N6W)[16] and the holo (PDB id: 3O2G)[17] structures of gamma-butyrobetaine dioxygenase have been solved, demonstrating an induced fit mechanism may contribute to the catalytic activity of gamma-butyrobetaine dioxygenase.
Gamma-butyrobetaine dioxygenase is promiscuous in substrate selectivity and it processes a number of modified substrates, including the natural catalytic products L-carnitine and D-carnitine, forming 3-dehydrocarnitine and trimethylaminoacetone.[17][18] Gamma-butyrobetaine dioxygenase also catalyses the oxidation of mildronate[19] to form multiple products including malonic acid semialdehyde, dimethylamine, formaldehyde and (1-methylimidazolidin-4-yl)acetic acid, which is proposed to be formed via a Stevens rearrangement mechanism.[20][21] Gamma-butyrobetaine dioxygenase is unique among other human 2OG oxygenases that it catalyses both hydroxylation (e.g.: L-carnitine), demethylation (e.g.: formaldehyde) and C-C bond formation (e.g.: (1-methylimidazolidin-4-yl)acetic acid).[22]
Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols.[1][2] Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vitamin E,[3] can cause nerve problems.[4] Vitamin E is a fat-soluble antioxidant which may help protect cell membranes from reactive oxygen species.[2][4] Worldwide, government organizations recommend adults consume in the range of 3 to 15 mg per day. As of 2016, consumption was below recommendations according to a worldwide summary of more than one hundred studies that reported a median dietary intake of 6.2 mg per day for alpha-tocopherol.[5] Foods rich in vitamin E include seeds and nuts, seed oils, peanut butter, and vitamin E-fortified foods, such as margarine.[2][4]
Population studies suggested that people who consumed foods with more vitamin E, or who chose on their own to consume a vitamin E dietary supplement, had lower incidence of cardiovascular diseases, cancer, dementia, and other diseases. However, placebo-controlled clinical trials using alpha-tocopherol as a supplement, with daily amounts as high as 2,000 mg per day, could not always replicate these findings.[2] In the United States vitamin E supplement use peaked around 2002, but has declined by more than half by 2006. The authors theorized that declining use may have been due to publications of large placebo-controlled studies that showed either no benefits or actual negative consequences from high-dose vitamin E.[6][7][8]
Both natural and synthetic tocopherols are subject to oxidation, so dietary supplements are esterified, creating tocopheryl acetate for stability purposes.[2][9] Tocopherols and tocotrienols both occur in α (alpha), β (beta), γ (gamma), and δ (delta) forms, as determined by the number and position of methyl groups on the chromanol ring.[4][10] All eight of these vitamers feature a chromane double ring, with a hydroxyl group that can donate a hydrogen atom to reduce free radicals, and a hydrophobic side chain that allows for penetration into biological membranes.
Vitamin E was discovered in 1922, isolated in 1935, and first synthesized in 1938. Because the vitamin activity was first identified as essential for fertilized eggs to result in live births (in rats), it was given the name "tocopherol" from Greek words meaning birth and to bear or carry. Alpha-tocopherol, either naturally extracted from plant oils or, most commonly, as the synthetic tocopheryl acetate, is sold as a popular dietary supplement, either by itself or incorporated into a multivitamin product, and in oils or lotions for use on skin.
Chemistry
General chemical structure of tocopherols
RRR alpha-tocopherol; chiral points are where the three dashed lines connect to the side chain
The nutritional content of vitamin E is defined by equivalency to 100% RRR-configuration α-tocopherol activity. The molecules that contribute α-tocopherol activity are four tocopherols and four tocotrienols, within each group of four identified by the prefixes alpha- (α-), beta- (β-), gamma- (γ-), and delta- (δ-). For alpha(α)-tocopherol each of the three "R" sites has a methyl group (CH3) attached. For beta(β)-tocopherol: R1 = methyl group, R2 = H, R3 = methyl group. For gamma(γ)-tocopherol: R1 = H, R2 = methyl group, R3 = methyl group. For delta(δ)-tocopherol: R1 = H, R2 = H, R3 = methyl group. The same configurations exist for the tocotrienols, except that the hydrophobic side chain has three carbon-carbon double bonds whereas the tocopherols have a saturated side chain.[11]
Stereoisomers
In addition to distinguishing tocopherols and tocotrienols by position of methyl groups, the tocopherols have a phytyl tail with three chiral points or centers that can have a right or left orientation. The naturally occurring plant form of alpha-tocopherol is RRR-α-tocopherol, also referred to as d-tocopherol, whereas the synthetic form (all-racemic or all-rac vitamin E, also dl-tocopherol) is equal parts of eight stereoisomers RRR, RRS, RSS, SSS, RSR, SRS, SRR and SSR with progressively decreasing biological equivalency, so that 1.36 mg of dl-tocopherol is considered equivalent to 1.0 mg of d-tocopherol, the natural form. Rephrased, the synthetic has 73.5% of the potency of the natural.[11]
Form Structure
alpha-Tocopherol
beta-Tocopherol
gamma-Tocopherol
delta-Tocopherol
Tocopheryl acetate
Tocopherols
Alpha-tocopherol is a lipid-soluble antioxidant functioning within the glutathione peroxidase pathway,[12] and protecting cell membranes from oxidation by reacting with lipid radicals produced in the lipid peroxidation chain reaction.[2][13] This removes the free radical intermediates and prevents the oxidation reaction from continuing. The oxidized α-tocopheroxyl radicals produced in this process may be recycled back to the active reduced form through reduction by other antioxidants, such as ascorbate, retinol or ubiquinol.[14] Other forms of vitamin E have their own unique properties; for example, γ-tocopherol is a nucleophile that can react with electrophilic mutagens.[10]
Tocotrienols
The four tocotrienols (alpha, beta, gamma, delta) are similar in structure to the four tocopherols, with the main difference being that the former have hydrophobic side chains with three carbon-carbon double bonds, whereas the tocopherols have saturated side chains. For alpha(α)-tocotrienol each of the three "R" sites has a methyl group (CH3) attached. For beta(β)-tocotrienol: R1 = methyl group, R2 = H, R3 = methyl group. For gamma(γ)-tocotrienol: R1 = H, R2 = methyl group, R3 = methyl group. For delta(δ)-tocotrienol: R1 = H, R2 = H, R3 = methyl group. Palm oil is a good source of alpha and gamma tocotrienols.[15]
Tocotrienols have only a single chiral center, which exists at the 2' chromanol ring carbon, at the point where the isoprenoid tail joins the ring. The other two corresponding centers in the phytyl tail of the corresponding tocopherols do not exist as chiral centers for tocotrienols due to unsaturation (C-C double bonds) at these sites. Tocotrienols extracted from plants are always dextrorotatory stereoisomers, signified as d-tocotrienols. In theory, levorotatory forms of tocotrienols (l-tocotrienols) could exist as well, which would have a 2S rather than 2R configuration at the molecules' single chiral center, but unlike synthetic dl-alpha-tocopherol, the marketed tocotrienol dietary supplements are extracted from palm oil.[16] A number of health benefits of tocotrienols have been proposed, including decreased risk of age-associated cognitive impairment, heart disease and cancer. The evidence is not conclusive.[17][18][19]
Functions
Tocopherols function by donating H atoms to radicals (X).
Vitamin E may have various roles as a vitamin.[4] Many biological functions have been postulated, including a role as a fat-soluble antioxidant.[4] In this role, vitamin E acts as a radical scavenger, delivering a hydrogen (H) atom to free radicals. At 323 kJ/mol, the O-H bond in tocopherols is about 10% weaker than in most other phenols.[20] This weak bond allows the vitamin to donate a hydrogen atom to the peroxyl radical and other free radicals, minimizing their damaging effect. The thus-generated tocopheryl radical is recycled to tocopherol by a redox reaction with a hydrogen donor, such as vitamin C.[21]
Vitamin E affects gene expression[22] and is an enzyme activity regulator, such as for protein kinase C (PKC) – which plays a role in smooth muscle growth – with vitamin E participating in deactivation of PKC to inhibit smooth muscle growth.[23]
Synthesis
Biosynthesis
Photosynthesizing plants, algae and cyanobacteria synthesize tocochromanols, the chemical family of compounds made up of four tocopherols and four tocotrienols; in a nutrition context this family is referred to as Vitamin E. Biosynthesis starts with formation of the closed-ring part of the molecule as homogentisic acid (HGA). The side chain is attached (saturated for tocopherols, polyunsaturated for tocotrienols). The pathway for both is the same, so that gamma- is created and from that alpha-, or delta- is created and from that the beta- compounds.[24][25] Biosynthesis takes place in the plastids.[25]
As to why plants synthesize tocochromanols, the major reason appears to be for antioxidant activity. Different parts of plants, and different species, are dominated by different tocochromanols. The predominant form in leaves, and hence leafy green vegetables, is α-tocopherol.[24] Location is in chloroplast membranes, in close proximity to the photosynthetic process.[25] The function is to protect against damage from the ultraviolet radiation of sunlight. Under normal growing conditions the presence of α-tocopherol does not appear to be essential, as there are other photo-protective compounds, and plants that through mutations have lost the ability to synthesize α-tocopherol demonstrate normal growth. However, under stressed growing conditions such as drought, elevated temperature or salt-induced oxidative stress, the plants' physiological status is superior if it has the normal synthesis capacity.[26]
Seeds are lipid-rich, to provide energy for germination and early growth. Tocochromanols protect the seed lipids from oxidizing and becoming rancid.[24][25] The presence of tocochromanols extends seed longevity, and promotes successful germination and seedling growth.[26] Gamma-tocopherol dominates in seeds of most plant species, but there are exceptions. For canola, corn and soy bean oils, there is more γ-tocopherol than α-tocopherol, but for safflower, sunflower and olive oils the reverse is true.[24][25][15] Of the commonly used food oils, palm oil is unique in that tocotrienol content is higher than tocopherol content.[15] Seed tocochromanols content is also dependent on environmental stressors. In almonds, for example, drought or elevated temperature increase α-tocopherol and γ-tocopherol content of the nuts. The same article mentions that drought increases the tocopherol content of olives, and heat likewise for soybeans.[27]
Vitamin E biosynthesis occurs in the plastid and goes through two different pathways: the Shikimate pathway and the Methylerythritol Phosphate pathway (MEP pathway).[24] The Shikimate pathway generates the chromanol ring from the Homogentisic Acid (HGA) and the MEP pathway produces the hydrophobic tail which differs between tocopherol and tocotrienol. The synthesis of the specific tail is dependent on which molecule it originates from. In a tocopherol, its prenyl tail emerges from the geranylgeranyl diphosphate (GGDP) group, while the phytyl tail of a tocotrienol stems from a phytyl diphosphate.[24]
Industrial synthesis
The synthetic product is all-rac-alpha-tocopherol,[28] also referred to as dl-alpha tocopherol. It consists of eight stereoisomers (RRR, RRS, RSS, RSR, SRR, SSR, SRS and SSS) in equal quantities. "It is synthesized from a mixture of toluene and 2,3,5-trimethyl-hydroquinone that reacts with isophytol to all-rac-alpha-tocopherol, using iron in the presence of hydrogen chloride gas as catalyst. The reaction mixture obtained is filtered and extracted with aqueous caustic soda. Toluene is removed by evaporation and the residue (all rac-alpha-tocopherol) is purified by vacuum distillation."[28] The natural alpha tocopherol extracted from plants is RRR-alpha tocopherol, referred to as d-alpha-tocopherol.[29] The synthetic has 73.5% of the potency of the natural.[30] Manufacturers of dietary supplements and fortified foods for humans or domesticated animals convert the phenol form of the vitamin to an ester using either acetic acid or succinic acid because the esters are more chemically stable, providing for a longer shelf-life.[2][31]
Deficiency
Main article: Vitamin E deficiency
Vitamin E deficiency is rare in humans, occurring as a consequence of abnormalities in dietary fat absorption or metabolism rather than from a diet low in vitamin E.[3] One example of a genetic abnormality in metabolism is mutations of genes coding for alpha-tocopherol transfer protein (α-TTP). Humans with this genetic defect exhibit a progressive neurodegenerative disorder known as ataxia with vitamin E deficiency (AVED) despite consuming normal amounts of vitamin E. Large amounts of alpha-tocopherol as a dietary supplement are needed to compensate for the lack of α-TTP.[32][33] Vitamin E deficiency due to either malabsorption or metabolic anomaly can cause nerve problems due to poor conduction of electrical impulses along nerves due to changes in nerve membrane structure and function. In addition to ataxia, vitamin E deficiency can cause peripheral neuropathy, myopathies, retinopathy, and impairment of immune responses.[3][4]
Drug interactions
The amounts of alpha-tocopherol, other tocopherols and tocotrienols that are components of dietary vitamin E, when consumed from foods, do not appear to cause any interactions with drugs. Consumption of alpha-tocopherol as a dietary supplement in amounts in excess of 300 mg/day may lead to interactions with aspirin, warfarin and cyclosporine A in ways that alter function.[4][34] For aspirin and warfarin, high amounts of vitamin E may potentiate anti-blood clotting action.[4][34] In multiple clinical trials, vitamin E lowered blood concentration of the immunosuppressant medication, cyclosporine A.[34] The US National Institutes of Health, Office of Dietary Supplements, raises a concern that co-administration of vitamin E could counter the mechanisms of anti-cancer radiation therapy and some types of chemotherapy, and so advises against its use in these patient populations. The references it cited reported instances of reduced treatment adverse effects, but also poorer cancer survival, raising the possibility of tumor protection from the intended oxidative damage by the treatments.[4]
Dietary recommendations
US vitamin E recommendations (mg per day)[3]
AI (children ages 0–6 months) 4
AI (children ages 7–12 months) 5
RDA (children ages 1–3 years) 6
RDA (children ages 4–8 years) 7
RDA (children ages 9–13 years) 11
RDA (children ages 14–18 years) 15
RDA (adults ages 19+) 15
RDA (pregnancy) 15
RDA (lactation) 19
UL (adults) 1,000
The U.S. National Academy of Medicine updated estimated average requirements (EARs) and recommended dietary allowances (RDAs) for vitamin E in 2000. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. Adequate intakes (AIs) are identified when there is not sufficient information to set EARs and RDAs. The EAR for vitamin E for women and men ages 14 and up is 12 mg/day. The RDA is 15 mg/day.[3] As for safety, tolerable upper intake levels ("upper limits" or ULs) are set for vitamins and minerals when evidence is sufficient. Hemorrhagic effects in rats were selected as the critical endpoint to calculate the upper limit via starting with the lowest-observed-adverse-effect-level. The result was a human upper limit set at 1000 mg/day.[3] Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes.[3]
The European Food Safety Authority (EFSA) refers to the collective set of information as dietary reference values, with population reference intakes (PRIs) instead of RDAs, and average requirements instead of EARs. AIs and ULs are defined the same as in the United States. For women and men ages 10 and older, the PRIs are set at 11 and 13 mg/day, respectively. PRI for pregnancy is 11 mg/day, for lactation 11 mg/day. For children ages 1–9 years the PRIs increase with age from 6 to 9 mg/day.[35] The EFSA used an effect on blood clotting as a safety-critical effect. It identified that no adverse effects were observed in a human trial as 540 mg/day, used an uncertainty factor of 2 to derive an upper limit of half of that, then rounded to 300 mg/day.[36]
The Japan National Institute of Health and Nutrition set adult AIs at 6.5 mg/day (females) and 7.0 mg/day (males), and 650–700 mg/day (females), and 750–900 mg/day (males) for upper limits, amounts depending on age.[37] India recommends an intake of 8–10 mg/day and does not set an upper limit.[38] The World Health Organization recommends that adults consume 10 mg/day.[5] The United Kingdom is an outlier, in that it recommends 4 mg/day for adult men and 3 mg/day for adult women.[39]
Consumption is below these government recommendations. Government survey results in the United States reported average consumption for adult females at 8.4 mg/d and adult males 10.4 mg/d.[40] Both are below the RDA of 15 mg/day. A worldwide summary of more than one hundred studies reported a median dietary intake of 6.2 mg/d for alpha-tocopherol.[5]
Food labeling
For U.S. food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of daily value. For vitamin E labeling purposes 100% of the daily value was 30 international units, but as of 27 May 2016, it was revised to 15 mg to bring it into agreement with the RDA.[41] A table of the old and new adult daily values is provided at Reference Daily Intake.
European Union regulations require that labels declare energy, protein, fat, saturated fat, carbohydrates, sugars, and salt. Voluntary nutrients may be shown if present in significant amounts. Instead of daily values, amounts are shown as percent of reference intakes (RIs). For vitamin E, 100% RI was set at 12 mg in 2011.[42]
The international unit measurement was used by the United States in 1968–2016. 1 IU is the biological equivalent of about 0.667 mg d (RRR)-alpha-tocopherol (2/3 mg exactly), or of 0.90 mg of dl-alpha-tocopherol, corresponding to the then-measured relative potency of stereoisomers. In May 2016, the measurements have been revised, such that 1 mg of "Vitamin E" is 1 mg of d-alpha-tocopherol or 2 mg of dl-alpha-tocopherol.[43] The change was originally started in 2000, when forms of Vitamin E other than alpha-tocopherol was dropped from dietary calculations by the IOM. The UL amount disregards any conversion.[44] The EFSA has never used an IU unit, and their measurement only considers RRR-alpha-tocopherol.[45]
Sources
Worldwide, consumption is below recommendations according to a summary of more than one hundred studies that reported a median dietary intake of 6.2 mg per day for alpha-tocopherol.[5] Of the many different forms of vitamin E, gamma-tocopherol (γ-tocopherol) is the most common form found in the North American diet, but alpha-tocopherol (α-tocopherol) is the most biologically active.[2][46] Palm oil is a source of tocotrienols.[16]
The U.S. Department of Agriculture (USDA), Agricultural Research Services, maintains a food composition database. The last major revision was Release 28, September 2015. In addition to the naturally occurring sources shown in the table,[47] certain ready-to-eat cereals, infant formulas, liquid nutrition products and other foods are fortified with alpha-tocopherol.[47]
Plant source[47] Amount
(mg / 100 g)
Wheat germ oil 150
Hazelnut oil 47
Canola/rapeseed oil 44
Sunflower oil 41.1
Almond oil 39.2
Safflower oil 34.1
Grapeseed oil 28.8
Sunflower seed kernels 26.1
Almonds 25.6
Almond butter 24.2
Plant source[47] Amount
(mg / 100 g)
Canola oil 17.5
Palm oil 15.9
Peanut oil 15.7
Margarine, tub 15.4
Hazelnuts 15.3
Corn oil 14.8
Olive oil 14.3
Soybean oil 12.1
Pine nuts 9.3
Peanut butter 9.0
Plant source[47] Amount
(mg / 100 g)
Popcorn 5.0
Pistachio nuts 2.8
Avocados 2.6
Spinach, raw 2.0
Asparagus 1.5
Broccoli 1.4
Cashew nuts 0.9
Bread 0.2-0.3
Rice, brown 0.2
Potato, Pasta <0.1
Animal source[47] Amount
(mg / 100 g)
Fish 1.0-2.8
Oysters 1.7
Butter 1.6
Cheese 0.6-0.7
Eggs 1.1
Chicken 0.3
Beef 0.1
Pork 0.1
Milk, whole 0.1
Milk, skim 0.01
Supplements
Softgel capsules used for large amounts of vitamin E
Vitamin E is fat soluble, so dietary supplement products are usually in the form of the vitamin, esterified with acetic acid to generate tocopheryl acetate, and dissolved in vegetable oil in a softgel capsule.[2] For alpha-tocopherol, amounts range from 100 to 1000 IU per serving. Smaller amounts are incorporated into multi-vitamin/mineral tablets. Gamma-tocopherol and tocotrienol supplements are also available from dietary supplement companies. The latter are extracts from palm oil.[16]
Fortification
The World Health Organization does not have any recommendations for food fortification with vitamin E.[48] The Food Fortification Initiative does not list any countries that have mandatory or voluntary programs for vitamin E.[49] Infant formulas have alpha-tocopherol as an ingredient. In some countries, certain brands of ready-to-eat cereals, liquid nutrition products and other foods have alpha-tocopherol as an added ingredient.[47]
Non-nutrient food additives
Various forms of vitamin E are common food additive in oily food, used to deter rancidity caused by peroxidation. Those with an E number include:[50]
E306 Tocopherol-rich extract (mixed, natural, can include tocotrienol)
E307 Alpha-tocopherol (synthetic)
E308 Gamma-tocopherol (synthetic)
E309 Delta-tocopherol (synthetic)
These E numbers include all racemic forms and acetate esters thereof.[50] Commonly found on food labels in Europe and some other countries, their safety assessment and approval are the responsibility of the European Food Safety Authority.[51]
Absorption, metabolism, excretion
Tocotrienols and tocopherols, the latter including the stereoisomers of synthetic alpha-tocopherol, are absorbed from the intestinal lumen, incorporated into chylomicrons, and secreted into the portal vein, leading to the liver. Absorption efficiency is estimated at 51% to 86%,[3] and that applies to all of the vitamin E family – there is no discrimination among the vitamin E vitamers during absorption. Bile is necessary for chylomicron formation, so disease conditions such as cystic fibrosis result in biliary insufficiency and vitamin E malabsorption.[1] When consumed as an alpha-tocopheryl acetate dietary supplement, absorption is promoted when consumed with a fat-containing meal.[1] Unabsorbed vitamin E is excreted via feces. Additionally, vitamin E is excreted by the liver via bile into the intestinal lumen, where it will either be reabsorbed or excreted via feces, and all of the vitamin E vitamers are metabolized and then excreted via urine.[3][11]
Upon reaching the liver, RRR-alpha-tocopherol is preferentially taken up by alpha-tocopherol transfer protein (α-TTP). All other forms are degraded to 2'-carboxethyl-6-hydroxychromane (CEHC), a process that involves truncating the phytic tail of the molecule, then either sulfated or glycuronidated. This renders the molecules water-soluble and leads to excretion via urine. Alpha-tocopherol is also degraded by the same process, to 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychromane (α-CEHC), but more slowly because it is partially protected by α-TTP. Large intakes of α-tocopherol result in increased urinary α-CEHC, so this appears to be a means of disposing of excess vitamin E.[3][11]
Alpha-tocopherol transfer protein is coded by the TTPA gene on chromosome 8. The binding site for RRR-α-tocopherol is a hydrophobic pocket with a lower affinity for beta-, gamma-, or delta-tocopherols, or for the stereoisomers with an S configuration at the chiral 2 site. Tocotrienols are also a poor fit because the double bonds in the phytic tail create a rigid configuration that is a mismatch with the α-TTP pocket.[11] A rare genetic defect of the TTPA gene results in people exhibiting a progressive neurodegenerative disorder known as ataxia with vitamin E deficiency (AVED) despite consuming normal amounts of vitamin E. Large amounts of alpha-tocopherol as a dietary supplement are needed to compensate for the lack of α-TTP.[32] The role of α-TTP is to move α-tocopherol to the plasma membrane of hepatocytes (liver cells), where it can be incorporated into newly created very low density lipoprotein (VLDL) molecules. These convey α-tocopherol to cells in the rest of the body. As an example of a result of the preferential treatment, the US diet delivers approximately 70 mg/d of γ-tocopherol and plasma concentrations are on the order of 2–5 μmol/L; meanwhile, dietary α-tocopherol is about 7 mg/d but plasma concentrations are in the range of 11–37 μmol/L.[11]
Affinity of α-TTP for vitamin E vitamers[11]
Vitamin E compound Affinity
RRR-alpha-tocopherol 100%
beta-tocopherol 38%
gamma-tocopherol 9%
delta-tocopherol 2%
SSR-alpha-tocopherol 11%
alpha-tocotrienol 12%
Testing for levels
A worldwide summary of more than one hundred human studies reported a median of 22.1 μmol/L for serum α-tocopherol, and defined α-tocopherol deficiency as less than 12 μmol/L. It cited a recommendation that serum α-tocopherol concentration be ≥30 μmol/L to optimize health benefits.[5] In contrast, the U.S. Dietary Reference Intake text for vitamin E concluded that a plasma concentration of 12 μmol/L was sufficient to achieve normal ex vivo hydrogen peroxide-induced hemolysis.[3] A 2014 review defined less than 9 μmol/L as deficient, 9-12 μmol/L as marginal, and greater than 12 μmol/L as adequate.[52]
Serum concentration increases with age. This is attributed to the fact that vitamin E circulates in blood incorporated into lipoproteins, and serum lipoprotein concentrations increase with age. Infants and young children have a higher risk of being below the deficiency threshold.[5] Cystic fibrosis and other fat malabsorption conditions can result in low serum vitamin E. Dietary supplements will raise serum vitamin E.[3]
Medical applications
For the conditions described below, the results of randomized clinical trials (RCTs) do not always concur with the observational evidence.[2] This could be a matter of amount. Observational studies compare low consumers to high consumers based on intake from food. Diets higher in vitamin E may contain other compounds that convey health benefits, or be consumed by people who make non-diet lifestyle choices that lower disease risk, so that the observed effect may not be due to the vitamin E content. Meanwhile, many of the published RCTs used amounts of alpha-tocopherol 20X to 30X higher than what can be achieved from food.[8]
Declining supplement use
In the United States, vitamin E supplement use by female health professionals was 16.1% in 1986, 46.2% in 1998, 44.3% in 2002, but decreased to 19.8% in 2006. Similarly, for male health professionals, rates for same years were 18.9%, 52.0%, 49.4% and 24.5%. The authors theorized that declining use in these populations may have been due to publications of studies that showed either no benefits or negative consequences from vitamin E supplements.[6] Within the U.S. military services, vitamin prescriptions written for active, reserve and retired military, and their dependents, were tracked over years 2007–2011. Vitamin E prescriptions decreased by 53% while vitamin C remained constant and vitamin D increased by 454%.[53] A report on vitamin E sales volume in the US documented a 50% decrease between 2000 and 2006,[7] with a potential reason being a meta-analysis that concluded high-dosage (≥400 IU/d for at least 1 year) vitamin E was associated with an increase in all-cause mortality.[54]
All-cause mortality
Two meta-analyses concluded that as a dietary supplement, vitamin E neither improved nor impaired all-cause mortality.[55][56] An older meta-analysis had concluded high-dosage (≥400 IU/d for at least 1 year) vitamin E was associated with an increase in all-cause mortality. The authors acknowledged that the cited high-dose trials were often small and performed with people who already had chronic diseases.[54] A meta-analysis of long-term clinical trials reported a non-significant 2% increase in all-cause mortality when alpha-tocopherol was the only supplement used. The same meta-analysis reported a statistically significant 3% increase for results when alpha-tocopherol was used in combination with other nutrients (vitamin A, vitamin C, beta-carotene, selenium).[8]
Age-related macular degeneration
No changes seen for risk of developing age-related macular degeneration from long-term vitamin E suplementation.[57]
Alzheimer's disease
An older review of dietary intake studies reported that higher consumption of vitamin E from foods lowered the risk of developing Alzheimer's disease (AD) by 24%.[58] A 2017 Cochrane review reported on vitamin E as a potential dietary benefit for mild cognitive impairment (MCI) and Alzheimer's disease. Based on evidence from one trial in each of the categories, the study found insufficient evidence for supplemental vitamin E to prevent progression from MCI to dementia, but it did indicate slowing of functional decline in people with AD. Given the small number of trials and subjects, the authors recommended further research.[59] A 2018 meta-analysis found lower vitamin E blood levels in AD people compared to healthy, age-matched people.[60] In 2017, a consensus statement from the British Association for Psychopharmacology concluded that, until further information is available, vitamin E cannot be recommended for treatment or prevention of Alzheimer's disease.[61]
Cancer
In a 2022 update of an earlier report, the United States Preventive Services Task Force recommended against the use of vitamin E supplements for the prevention of cardiovascular disease or cancer, concluding there was insufficient evidence to assess the balance of benefits and harms, yet also concluding with moderate certainty that there is no net benefit of supplementation.[62]
As for literature on different types of cancer, an inverse relationship between dietary vitamin E and kidney cancer and bladder cancer is seen in observational studies. The risk reduction was 19% when highest and lowest intake groups were compared. The authors concluded that randomized controlled trials are needed.[63][64] A large study comparing placebo to an all rac-alpha-tocopherol group consuming 400 IU/day reported no difference in bladder cancer cases.[65] An inverse relationship between dietary vitamin E and lung cancer was reported in observational studies. The relative risk reduction was 16% when highest and lowest intake groups were compared. The benefit was progressive as dietary intake increased from 2 mg/day to 16 mg/day. The authors noted that the findings need to be confirmed by prospective studies.[66] One such large trial, which compared 50 mg alpha-tocopherol to placebo in male tobacco smokers, reported no impact on lung cancer.[67] A trial which tracked people who chose to consume a vitamin E dietary supplement reported an increased risk of lung cancer for those consuming more than 215 mg/day.[68]
For prostate cancer, there are also conflicting results. A meta-analysis based on serum alpha-tocopherol content reported an inverse correlation, with the difference between lowest and highest a 21% reduction in relative risk.[69] In contrast, a meta-analysis of observational studies reported no relationship for dietary vitamin E intake.[70] There were also conflicting results from large RCTs. The ATBC trial administered placebo or 50 mg/day alpha-tocopherol to male tobacco smokers for 5 to 8 years and reported a 32% decrease in the incidence of prostate cancer.[71] Conversely, the SELECT trial of selenium and vitamin E for prostate cancer enrolled men ages 55 or older, mostly non-smokers, to consume a placebo or a 400 IU/day dietary supplement. It reported relative risk as a statistically significant 17% higher for the vitamin group.[72]
For colorectal cancer, a systematic review identified RCTs of vitamin E and placebo followed for 7–10 years. There was a non-significant 11% decrease in relative risk.[73] The SELECT trial (men over 55 years, placebo or 400 IU/day) also reported on colorectal cancer. There was a non-significant 3% increase in adenoma occurrence compared to placebo.[74] The Women's Health Study reported no significant differences for incidences of all types of cancer, cancer deaths, or specifically for breast, lung or colon cancers.[75]
Potential confounding factors are the form of vitamin E used in prospective studies and the amounts. Synthetic, racemic mixtures of vitamin E isomers are not bioequivalent to natural, non-racemic mixtures, yet are widely used in clinical trials and as dietary supplement ingredients.[76] One review reported a modest increase in cancer risk with vitamin E supplementation while stating that more than 90% of the cited clinical trials used the synthetic, racemic form dl-alpha-tocopherol.[68]
Cancer health claims
The U.S. Food and Drug Administration initiated a process of reviewing and approving food and dietary supplement health claims in 1993. Reviews of petitions results in proposed claims being rejected or approved. If approved, specific wording is allowed on package labels. In 1999, a second process for claims review was created. If there is not a scientific consensus on the totality of the evidence, a Qualified Health Claim (QHC) may be established. The FDA does not "approve" qualified health claim petitions. Instead, it issues a Letter of Enforcement Discretion that includes very specific claim language and the restrictions on using that wording.[77] The first QHCs relevant to vitamin E were issued in 2003: "Some scientific evidence suggests that consumption of antioxidant vitamins may reduce the risk of certain forms of cancer." In 2009, the claims became more specific, allowing that vitamin E might reduce the risk of renal, bladder and colorectal cancers, but with required mention that the evidence was deemed weak and the claimed benefits highly unlikely. A petition to add brain, cervical, gastric and lung cancers was rejected. A further revision, May 2012, allowed that vitamin E may reduce risk of renal, bladder and colorectal cancers, with a more concise qualifier sentence added: "FDA has concluded that there is very little scientific evidence for this claim." Any company product label making the cancer claims has to include a qualifier sentence.[78]
Cataracts
A meta-analysis from 2015 reported that for studies which reported serum tocopherol, higher serum concentration was associated with a 23% reduction in relative risk of age-related cataracts (ARC), with the effect due to differences in nuclear cataract rather than cortical or posterior subcapsular cataract – the three major classifications of age-related cataracts.[79] However, this article and a second meta-analysis reporting on clinical trials of alpha-tocopherol supplementation reported no statistically significant change to risk of ARC when compared to placebo.[79][80]
Cardiovascular diseases
In an 2022 update of an earlier report, the United States Preventive Services Task Force recommended against the use of vitamin E supplements for the prevention of cardiovascular disease or cancer, concluding there was insufficient evidence to assess the balance of benefits and harms, yet also concluding with moderate certainty that there is no net benefit of supplementation.[62]
Research on the effects of vitamin E on cardiovascular disease has produced conflicting results. In theory, oxidative modification of LDL-cholesterol promotes blockages in coronary arteries that lead to atherosclerosis and heart attacks, so vitamin E functioning as an antioxidant would reduce oxidized cholesterol and lower risk of cardiovascular disease. Vitamin E status has also been implicated in the maintenance of normal endothelial cell function of cells lining the inner surface of arteries, anti-inflammatory activity and inhibition of platelet adhesion and aggregation.[81] An inverse relation has been observed between coronary heart disease and the consumption of foods high in vitamin E, and also higher serum concentration of alpha-tocopherol.[81][82] In one of the largest observational studies, almost 90,000 healthy nurses were tracked for eight years. Compared to those in the lowest fifth for reported vitamin E consumption (from food and dietary supplements), those in the highest fifth were at a 34% lower risk of major coronary disease.[83] The problem with observational studies is that these cannot confirm a relation between the lower risk of coronary heart disease an
nd vitamin E consumption because of confounding factors. Diet higher in vitamin E may also be higher in other, unidentified components that promote heart health, or people choosing such diets may be making other healthy lifestyle choices.[81][83]
There is some supporting evidence from randomized clinical trials (RCTs). A meta-analysis on the effects of alpha-tocopherol supplementation in RCTs on aspects of cardiovascular health reported that when consumed without any other antioxidant nutrient, the relative risk of heart attack was reduced by 18%.[84] The results were not consistent for all of the individual trials incorporated into the meta-analysis. For example, the Physicians' Health Study II did not show any benefit after 400 IU every other day for eight years, for heart attack, stroke, coronary mortality or all-cause mortality.[85] The HOPE/HOPE-TOO trial, which enrolled people with pre-existing vascular disease or diabetes into a multi-year trial of 400 IU/day, reported a higher risk of heart failure in the alpha-tocopherol group.[86]
The effects of vitamin E supplementation on incidence of stroke were summarized in 2011. There were no significant benefits for vitamin E versus placebo. Subset analysis for ischemic stroke, haemorrhagic stroke, fatal stroke, non-fatal stroke – all no significant difference in risk. Likewise for subset analysis of natural or synthetic vitamin E, or only above or below 300 IU/day, or whether the enrolled people were healthy or considered to be at higher than normal risk. The authors concluded that there was a lack of clinically important benefit of vitamin E supplementation in the prevention of stroke.[87] One large, multi-year study in which post-menopausal women consumed either placebo or 600 IU of natural-sourced vitamin E on alternate days reported no effect on stroke,[75] but did report a 21% reduction in relative risk of developing a deep vein clot or pulmonary embolism. The beneficial effect was strongest is the subset of women who had a history of a prior thrombotic event or who were genetically coded for clot risk (factor V Leiden or prothrombin mutation).[88]
Cardiovascular health claims
In 2001, the U.S. Food and Drug Administration rejected proposed health claims for vitamin E and cardiovascular health.[89] The U.S. National Institutes of Health reviewed literature published up to 2008 and concluded "In general, clinical trials have not provided evidence that routine use of vitamin E supplements prevents cardiovascular disease or reduces its morbidity and mortality."[4] The European Food Safety Authority (EFSA) reviews proposed health claims for the European Union countries. In 2010, the EFSA reviewed and rejected claims that a cause and effect relationship has been established between the dietary intake of vitamin E and maintenance of normal cardiac function or of normal blood circulation.[90]
Nonalcoholic fatty liver disease
Meta-analyses reported that supplemental vitamin E significantly reduced elevated liver enzymes, steatosis, inflammation and fibrosis, suggesting that the vitamin may be useful for treatment of nonalcoholic fatty liver disease (NAFLD) and the more extreme subset known as nonalcoholic steatohepatitis (NASH) in adults,[91][92] but not in children.[93][94]
Parkinson's disease
For Parkinson's disease, there is an observed inverse correlation seen with dietary vitamin E, but no confirming evidence from placebo-controlled clinical trials.[95][96]
Pregnancy
Antioxidant vitamins as dietary supplements have been proposed as having benefits if consumed during pregnancy. For the combination of vitamin E with vitamin C supplemented to pregnant women, a Cochrane review concluded that the data do not support vitamin E supplementation – majority of trials alpha-tocopherol at 400 IU/day plus vitamin C at 1,000 mg/day – as being efficacious for reducing risk of stillbirth, neonatal death, preterm birth, preeclampsia or any other maternal or infant outcomes, either in healthy women or those considered at risk for pregnancy complications.[97] The review identified only three small trials in which vitamin E was supplemented without co-supplementation with vitamin C. None of these trials reported any clinically meaningful information.[97]
Skin care
Vitamin E is included in some skincare and wound-treatment products,[98] but a 2015 meta-review found only "limited clinical evidence" of efficacy.[99] However the authors noted a dearth of research, stating that 23 of the 39 studies reviewed were "of limited quality with individual flaws, including low patient numbers, poor randomization, blinding, and short follow-up periods."
Topical
Although there is widespread use of tocopheryl acetate as a topical medication, with claims for improved wound healing and reduced scar tissue,[98] reviews have repeatedly concluded that there is insufficient evidence to support these claims.[99][100][101] There are reports of vitamin E-induced allergic contact dermatitis from use of vitamin-E derivatives such as tocopheryl linoleate and tocopherol acetate in skin care products. Incidence is low despite widespread use.[102]
Vaping-associated lung injury
Main article: Vaping-associated pulmonary injury
On 5 September 2019, the US Food and Drug Administration announced that 10 out of 18, or 56% of the samples of vape liquids sent in by states, linked to recent vaping related lung disease outbreak in the United States, tested positive for vitamin E acetate[103] which had been used as a thickening agent by illicit THC vape cartridge manufacturers.[104] On 8 November 2019, the Centers for Disease Control and Prevention identified vitamin E acetate as a very strong culprit of concern in the vaping-related illnesses, but has not ruled out other chemicals or toxicants as possible causes. These findings were based on fluid samples from the lungs of 29 patients with vaping-associated pulmonary injury, which provided direct evidence of vitamin E acetate at the primary site of injury in all the 29 lung fluid samples tested.[105] Vitamin E acetate was confirmed as a causitive agent.[106] Pyrolysis of vitamin E acetate produces a range of toxic gases.[107]
History
Vitamin E was discovered in 1922 by Herbert McLean Evans and Katharine Scott Bishop[108] and first isolated in a pure form by Evans and Gladys Anderson Emerson in 1935 at the University of California, Berkeley.[109] Because the vitamin activity was first identified as a dietary fertility factor in rats, it was given the name "tocopherol" from the Greek words "τόκος" [tókos, birth], and "φέρειν", [phérein, to bear or carry] meaning in sum "to carry a pregnancy," with the ending "-ol" signifying its status as a chemical alcohol. George M. Calhoun, Professor of Greek at the University of California, was credited with helping with the naming process.[110] Erhard Fernholz elucidated its structure in 1938 and shortly afterward the same year, Paul Karrer and his team first synthesized it.[111]
Nearly 50 years after the discovery of vitamin E, an editorial in the Journal of the American Medical Association titled "Vitamin in search of a disease" read in part "...research revealed many of the vitamin's secrets, but no certain therapeutic use and no definite deficiency disease in man." The animal discovery experiments had been a requirement for successful pregnancy, but no benefits were observed for women prone to miscarriage. Evidence for vascular health was characterized as unconvincing. The editorial closed with mention of some preliminary human evidence for protection against hemolytic anemia in young children.[112]
A role for vitamin E in coronary heart disease was first proposed in 1946 by Evan Shute and colleagues.[ More cardiovascular work from the same research group followed,[115] including a proposal that megadoses of vitamin E could slow down and even reverse the development of atherosclerosis.[116] Subsequent research showed no association between vitamin E supplementation and cardiovascular events such as nonfatal stroke or myocardial infarction, or cardiovascular mortality.[117]
There is a long history of belief that topical application of vitamin E containing oil benefits burn and wound healing.[98] This belief persists even though scientific reviews refuted this claim.[
The role of vitamin E in infant nutrition has a long research history. From 1949 onward there were trials with premature infants suggesting that oral alpha-tocopherol was protective against edema, intracranial hemorrhage, hemolytic anemia and retrolental fibroplasia.[118] A more recent review concluded that vitamin E supplementation in preterm infants reduced the risk of intercranial hemorrhage and retinopathy, but noted an increased risk of sepsis.[119]
Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism.[2] It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism.[3] It is important in the normal functioning of the nervous system via its role in the synthesis of myelin, and in the circulatory system in the maturation of red blood cells in the bone marrow.[2][4] Plants do not need cobalamin and carry out the reactions with enzymes that are not dependent on it.[5]
Vitamin B12 is the most chemically complex of all vitamins,[6] and for humans the only vitamin that must be sourced from animal-derived foods or supplements.[2][7] Only some archaea and bacteria can synthesize vitamin B12.[8] Vitamin B12 deficiency is a widespread condition that is particularly prevalent in populations with low consumption of animal foods. This can be due to a variety of reasons, such as low socioeconomic status, ethical considerations, or lifestyle choices such as veganism.[9]
Foods containing vitamin B12 include meat, shellfish, liver, fish, poultry, eggs, and dairy products.[2] Many breakfast cereals are fortified with the vitamin.[2] Supplements and medications are available to treat and prevent vitamin B12 deficiency.[2] They are usually taken by mouth, but for the treatment of deficiency may also be given as an intramuscular injection.[2][6]
Vitamin B12 deficiencies have a greater effect on the pregnant, young children, and elderly people, and are more common in middle and lower developed countries due to malnutrition.[10] The most common cause of vitamin B12 deficiency in developed countries is impaired absorption due to a loss of gastric intrinsic factor (IF) which must be bound to a food-source of B12 in order for absorption to occur.[11] A second major cause is an age-related decline in stomach acid production (achlorhydria), because acid exposure frees protein-bound vitamin.[12] For the same reason, people on long-term antacid therapy, using proton-pump inhibitors, H2 blockers or other antacids are at increased risk.[13]
The diets of vegetarians and vegans may not provide sufficient B12 unless a dietary supplement is taken.[2] A deficiency may be characterized by limb neuropathy or a blood disorder called pernicious anemia, a type of anemia in which red blood cells become abnormally large.[2] This can result in fatigue, decreased ability to think, lightheadedness, shortness of breath, frequent infections, poor appetite, numbness in the hands and feet, depression, memory loss, confusion, difficulty walking, blurred vision, irreversible nerve damage, and many others.[14] If left untreated in infants, deficiency may lead to neurological damage and anemia.[2] Folate levels in the individual may affect the course of pathological changes and symptomatology of vitamin B12 deficiency. Vitamin B12 deficiency in pregnant women is strongly associated with an increased risk of spontaneous abortion, congenital malformations such as neural tube defects, problems with brain development growth in the unborn child.[10]
Vitamin B12 was discovered as a result of pernicious anemia, an autoimmune disorder in which the blood has a lower than normal number of red blood cells, due to a deficiency of vitamin B12.[5][15] The ability to absorb the vitamin declines with age, especially in people over 60.[16]
Definition
Vitamin B12 is a coordination complex of cobalt, which occupies the center of a corrin ligand and is further bound to a benzimidazole ligand and adenosyl group.[17] A number of related species are known and these behave similarly, in particular all function as vitamins. This collection of compounds is sometimes referred to as "cobalamins". These chemical compounds have a similar molecular structure, each of which shows vitamin activity in a vitamin-deficient biological system, they are referred to as vitamers. The vitamin activity is as a coenzyme, meaning that its presence is required for some enzyme-catalyzed reactions.[12][18]
adenosylcobalamin
cyanocobalamin, the adenosyl ligand in vitamin B12 is replaced by cyanide.
hydroxocobalamin, the adenosyl ligand in vitamin B12 is replaced by hydroxide.
methylcobalamin, the adenosyl ligand in vitamin B12 is replaced by methyl.
Cyanocobalamin is a manufactured form of B12. Bacterial fermentation creates AdoB12 and MeB12, which are converted to cyanocobalamin by the addition of potassium cyanide in the presence of sodium nitrite and heat. Once consumed, cyanocobalamin is converted to the biologically active AdoB12 and MeB12. The two bioactive forms of vitamin B
12 are methylcobalamin in cytosol and adenosylcobalamin in mitochondria.
Cyanocobalamin is the most common form used in dietary supplements and food fortification because cyanide stabilizes the molecule against degradation. Methylcobalamin is also offered as a dietary supplement.[12] There is no advantage to the use of adenosylcobalamin or methylcobalamin forms for the treatment of vitamin B12 deficiency.[19][20][4]
Hydroxocobalamin can be injected intramuscularly to treat vitamin B12 deficiency. It can also be injected intravenously for the purpose of treating cyanide poisoning, as the hydroxyl group is displaced by cyanide, creating a non-toxic cyanocobalamin that is excreted in urine.
"Pseudovitamin B12" refers to compounds that are corrinoids with a structure similar to the vitamin but without vitamin activity.[21] Pseudovitamin B12 is the majority corrinoid in spirulina, an algal health food sometimes erroneously claimed as having this vitamin activity.[22]
Deficiency
Main article: Vitamin B12 deficiency
Vitamin B12 deficiency can potentially cause severe and irreversible damage, especially to the brain and nervous system.[6][23] Deficiency at levels only slightly lower than normal can cause a range of symptoms such as fatigue, feeling weak, lightheadedness, dizziness, breathlessness, headaches, mouth ulcers, upset stomach, decreased appetite, difficulty walking (staggering balance problems),[14][24] muscle weakness, depression, poor memory, poor reflexes, confusion, and pale skin, feeling abnormal sensations, among others, especially in people over age 60.[6][14][25] Vitamin B12 deficiency can also cause symptoms of mania and psychosis.[26][27] Among other problems, weakened immunity, reduced fertility and interruption of blood circulation in women may occur.[28]
The main type of vitamin B12 deficiency anemia is pernicious anemia,[29] characterized by a triad of symptoms:
Anemia with bone marrow promegaloblastosis (megaloblastic anemia). This is due to the inhibition of DNA synthesis (specifically purines and thymidine).
Gastrointestinal symptoms: alteration in bowel motility, such as mild diarrhea or constipation, and loss of bladder or bowel control.[30] These are thought to be due to defective DNA synthesis inhibiting replication in tissue sites with a high turnover of cells. This may also be due to the autoimmune attack on the parietal cells of the stomach in pernicious anemia. There is an association with gastric antral vascular ectasia (which can be referred to as watermelon stomach), and pernicious anemia.[31]
Neurological symptoms: sensory or motor deficiencies (absent reflexes, diminished vibration or soft touch sensation) and subacute combined degeneration of the spinal cord.[32] Deficiency symptoms in children include developmental delay, regression, irritability, involuntary movements and hypotonia.[33]
Vitamin B12 deficiency is most commonly caused by malabsorption, but can also result from low intake, immune gastritis, low presence of binding proteins, or use of certain medications.[6] Vegans—people who choose to not consume any animal-sourced foods—are at risk because plant-sourced foods do not contain the vitamin in sufficient amounts to prevent vitamin deficiency.[34] Vegetarians—people who consume animal byproducts such as dairy products and eggs, but not the flesh of any animal—are also at risk. Vitamin B12 deficiency has been observed in between 40% and 80% of the vegetarian population who do not also take a vitamin B12 supplement or consume vitamin-fortified food.[35] In Hong Kong and India, vitamin B12 deficiency has been found in roughly 80% of the vegan population. As with vegetarians, vegans can avoid this by consuming a dietary supplement or eating B12 fortified food such as cereal, plant-based milks, and nutritional yeast as a regular part of their diet.[36] The elderly are at increased risk because they tend to produce less stomach acid as they age, a condition known as achlorhydria, thereby increasing their probability of B12 deficiency due to reduced absorption.[2]
Nitrous oxide overdose or overuse converts the active monovalent form of vitamin B12 to the inactive bivalent form.[37]
Pregnancy, lactation and early childhood
The U.S. Recommended Dietary Allowance (RDA) for pregnancy is 2.6 μg/d, for lactation 2.8 μg/d. Determination of these values was based on an RDA of 2.4 μg/d for non-pregnant women, plus what will be transferred to the fetus during pregnancy and what will be delivered in breast milk.[12][38]: 972 However, looking at the same scientific evidence, the European Food Safety Authority (EFSA) sets adequate intake (AI) at 4.5 μg/d for pregnancy and 5.0 μg/d for lactation.[39] Low maternal vitamin B12, defined as serum concentration less than 148 pmol/L, increases the risk of miscarriage, preterm birth and newborn low birth weight.[40][38] During pregnancy the placenta concentrates B12, so that newborn infants have a higher serum concentration than their mothers.[12] As it is recently absorbed vitamin content that more effectively reaches the placenta, the vitamin consumed by the mother-to-be is more important than that contained in her liver tissue.[12][41]
Women who consume little animal-sourced food, or who are vegetarian or vegan, are at higher risk of becoming vitamin depleted during pregnancy than those who consume more animal products. This depletion can lead to anemia, and also an increased risk that their breastfed infants become vitamin deficient.[41][38] Vitamin B12 is not one of the supplements recommended by the World Health Organization for healthy women who are pregnant,[10] however vitamin B12 is often suggested during pregnancy in a multivitamin along with folic acid[42][43] especially for pregnant mothers who follow a vegetarian or vegan diet.[44]
Low vitamin concentrations in human milk occur in families with low socioeconomic status or low consumption of animal products.[38]: 971, 973 Only a few countries, primarily in Africa, have mandatory food fortification programs for either wheat flour or maize flour; India has a voluntary fortification program.[45] What the nursing mother consumes is more important than her liver tissue content, as it is recently absorbed vitamin that more effectively reaches breast milk.[38]: 973 Breast milk B12 decreases over months of nursing in both well-nourished and vitamin-deficient mothers.[38]: 973–974 Exclusive or near-exclusive breastfeeding beyond six months is a strong indicator of low serum vitamin status in nursing infants. This is especially true when the vitamin status was poor during the pregnancy and if the early-introduced foods fed to the still breastfeeding infant are vegan.[38]: 974–975
Risk of deficiency persists if the post-weaning diet is low in animal products.[38]: 974–975 Signs of low vitamin levels in infants and young children can include anemia, poor physical growth and neurodevelopmental delays.[38]: 975 Children diagnosed with low serum B12 can be treated with intramuscular injections, then transitioned to an oral dietary supplement.[38]: 976
Gastric bypass surgery
Various methods of gastric bypass or gastric restriction surgery are used to treat morbid obesity. Roux-en-Y gastric bypass surgery (RYGB) but not sleeve gastric bypass surgery or gastric banding, increases the risk of vitamin B12 deficiency and requires preventive post-operative treatment with either injected or high-dose oral supplementation.[46][47][48] For post-operative oral supplementation, 1000 μg/d may be needed to prevent vitamin deficiency.[48]
Diagnosis
According to one review: "At present, no 'gold standard' test exists for the diagnosis of vitamin B12 deficiency and as a consequence the diagnosis requires consideration of both the clinical state of the patient and the results of investigations."[49] The vitamin deficiency is typically suspected when a routine complete blood count shows anemia with an elevated mean corpuscular volume (MCV). In addition, on the peripheral blood smear, macrocytes and hypersegmented polymorphonuclear leukocytes may be seen. Diagnosis is supported based on vitamin B12 blood levels below 150–180 pmol/L (200–250 pg/mL) in adults.[50] However, serum values can be maintained while tissue B12 stores are becoming depleted. Therefore, serum B12 values above the cut-off point of deficiency do not necessarily confirm adequate B12 status.[2] For this reason, elevated serum homocysteine over 15 micromol/L and methylmalonic acid (MMA) over 0.271 micromol/L are considered better indicators of B12 deficiency, rather than relying only on the concentration of B12 in blood.[2] However, elevated MMA is not conclusive, as it is seen in people with B12 deficiency, but also in elderly people who have renal insufficiency,[27] and elevated homocysteine is not conclusive, as it is also seen in people with folate deficiency.[51] In addition, elevated methylmalonic acid levels may also be related to metabolic disorders such as methylmalonic acidemia.[52] If nervous system damage is present and blood testing is inconclusive, a lumbar puncture may be carried out to measure cerebrospinal fluid B12 levels.[53]
Serum haptocorrin binds 80-90% of circulating B12, rendering it unavailable for cellular delivery by transcobalamin II. This is conjectured to be a circulating storage function.[54] Several serious, even life-threatening diseases cause elevated serum HC, measured as abnormally high serum vitamin B12, while at the same time potentially manifesting as a symptomatic vitamin deficiency because of insufficient vitamin bound to transcobalamin II which transfers the vitamin to cells.[55]
Medical uses
A vitamin B12 solution (hydroxocobalamin) in a multi-dose bottle, with a single dose drawn up into a syringe for injection. Preparations are usually bright red.
Treatment of deficiency
Severe vitamin B12 deficiency is initially corrected with daily intramuscular injections of 1000 μg of the vitamin, followed by maintenance via monthly injections of the same amount or daily oral dosing of 1000 μg. The daily dose is far in excess of the vitamin requirement because the normal transporter protein mediated absorption is absent, leaving only very inefficient intestinal passive absorption.[56][57] Injection side effects include skin rash, itching, chills, fever, hot flushes, nausea and dizziness. Oral maintenance treatment avoids this problem and significantly reduces cost of treatment.[56][57]
Cyanide poisoning
For cyanide poisoning, a large amount of hydroxocobalamin may be given intravenously and sometimes in combination with sodium thiosulfate.[58][59] The mechanism of action is straightforward: the hydroxycobalamin hydroxide ligand is displaced by the toxic cyanide ion, and the resulting non-toxic cyanocobalamin is excreted in urine.[60]
free vitamin is transported into the portal circulation. The vitamin is then transferred to TC2, which serves as the circulating plasma transporter, Hereditary defects in production of TC2 and its receptor may produce functional deficiencies in B12 and infantile megaloblastic anemia, and abnormal B12 related biochemistry, even in some cases with normal blood B12 levels. For the vitamin to serve inside cells, the TC2-B12 complex must bind to a cell receptor protein and be endocytosed. TC2 is degraded within a lysosome, and free B12 is released into the cytoplasm, where it is transformed into the bioactive coenzyme by cellular enzymes.[116][118]
Malabsorption
Antacid drugs that neutralize stomach acid and drugs that block acid production (such as proton-pump inhibitors) will inhibit absorption of B12 by preventing release from food in the stomach.[119] Other causes of B12 malabsorption include intrinsic factor deficiency, pernicious anemia, bariatric surgery pancreatic insufficiency, obstructive jaundice, tropical sprue and celiac disease, and radiation enteritis of the distal ileum.[116] Age can be a factor. Elderly people are often achlorhydric due to reduced stomach parietal cell function, and thus have an increased risk of B12 deficiency.[120]
Storage and excretion
How fast B12 levels change depends on the balance between how much B12 is obtained from the diet, how much is secreted and how much is absorbed. The total amount of vitamin B12 stored in the body is about 2–5 mg in adults. Around 50% of this is stored in the liver. Approximately 0.1% of this is lost per day by secretions into the gut, as not all these secretions are reabsorbed. Bile is the main form of B12 excretion; most of the B12 secreted in the bile is recycled via enterohepatic circulation. Excess B12 beyond the blood's binding capacity is typically excreted in urine. Owing to the extremely efficient enterohepatic circulation of B12, the liver can store 3 to 5 years' worth of vitamin B12; therefore, nutritional deficiency of this vitamin is rare in adults in the absence of malabsorption disorders.[12] In the absence of intrinsic factor or distal ileum receptors, only months to a year of vitamin B12 are stored.[121]
Cellular reprogramming
Vitamin B12 through its involvement in one-carbon metabolism plays a key role in cellular reprogramming and tissue regeneration and epigenetic regulation. Cellular reprogramming is the process by which somatic cells can be converted to a pluripotent state. Vitamin B12 levels affect the histone modification H3K36me3, which suppresses illegitimate transcription outside of gene promoters. Mice undergoing in vivo reprogramming were found to become depleted in B12 and show signs of methionine starvation while supplementing reprogramming mice and cells with B12 increased reprogramming efficiency, indicating a cell-intrinsic effect.[122][123]
Synthesis
Biosynthesis
Main article: Cobalamin biosynthesis
Vitamin B12 is derived from a tetrapyrrolic structural framework created by the enzymes deaminase and cosynthetase which transform aminolevulinic acid via porphobilinogen and hydroxymethylbilane to uroporphyrinogen III. The latter is the first macrocyclic intermediate common to heme, chlorophyll, siroheme and B12 itself.[124][125] Later steps, especially the incorporation of the additional methyl groups of its structure, were investigated using 13C methyl-labelled S-adenosyl methionine. It was not until a genetically engineered strain of Pseudomonas denitrificans was used, in which eight of the genes involved in the biosynthesis of the vitamin had been overexpressed, that the complete sequence of methylation and other steps could be determined, thus fully establishing all the intermediates in the pathway.[126][127]
Species from the following genera and the following individual species are known to synthesize B12: Propionibacterium shermanii, Pseudomonas denitrificans, Streptomyces griseus, Acetobacterium, Aerobacter, Agrobacterium, Alcaligenes, Azotobacter, Bacillus, Clostridium, Corynebacterium, Flavobacterium, Lactobacillus, Micromonospora, Mycobacterium, Nocardia, Proteus, Rhizobium, Salmonella, Serratia, Streptococcus and Xanthomonas.[128][129]
Industrial
Industrial production of B12 is achieved through fermentation of selected microorganisms.[130] Streptomyces griseus, a bacterium once thought to be a fungus, was the commercial source of vitamin B12 for many years.[131] The species Pseudomonas denitrificans and Propionibacterium freudenreichii subsp. shermanii are more commonly used today.[130] These are grown under special conditions to enhance yield. Rhone-Poulenc improved yield via genetic engineering P. denitrificans.[132] Propionibacterium, the other commonly used bacteria, produce no exotoxins or endotoxins and are generally recognized as safe (have been granted GRAS status) by the Food and Drug Administration of the United States.[133]
The total world production of vitamin B12 in 2008 was 35,000 kg (77,175 lb).[134]
Laboratory
Main article: Vitamin B12 total synthesis
The complete laboratory synthesis of B12 was achieved by Robert Burns Woodward[135] and Albert Eschenmoser in 1972.[136][137] The work required the effort of 91 postdoctoral fellows (mostly at Harvard) and 12 PhD students (at ETH Zurich) from 19 nations. The synthesis constitutes a formal total synthesis, since the research groups only prepared the known intermediate cobyric acid, whose chemical conversion to vitamin B12 was previously reported. This synthesis of vitamin B12 is of no practical consequence due to its length, taking 72 chemical steps and giving an overall chemical yield well under 0.01%.[138] Although there have been sporadic synthetic efforts since 1972,[137] the Eschenmoser–Woodward synthesis remains the only completed (formal) total synthesis.
History
Further information: Vitamin § History
Descriptions of deficiency effects
Between 1849 and 1887, Thomas Addison described a case of pernicious anemia, William Osler and William Gardner first described a case of neuropathy, Hayem described large red cells in the peripheral blood in this condition, which he called "giant blood corpuscles" (now called macrocytes), Paul Ehrlich identified megaloblasts in the bone marrow, and Ludwig Lichtheim described a case of myelopathy.[139]
Identification of liver as an anti-anemia food
During the 1920s, George Whipple discovered that ingesting large amounts of raw liver seemed to most rapidly cure the anemia of blood loss in dogs, and hypothesized that eating liver might treat pernicious anemia.[140] Edwin Cohn prepared a liver extract that was 50 to 100 times more potent in treating pernicious anemia than the natural liver products. William Castle demonstrated that gastric juice contained an "intrinsic factor" which when combined with meat ingestion resulted in absorption of the vitamin in this condition.[139] In 1934, George Whipple shared the 1934 Nobel Prize in Physiology or Medicine with William P. Murphy and George Minot for discovery of an effective treatment for pernicious anemia using liver concentrate, later found to contain a large amount of vitamin B12.[139][141]
Identification of the active compound
While working at the Bureau of Dairy Industry, U.S. Department of Agriculture, Mary Shaw Shorb was assigned work on the bacterial strain Lactobacillus lactis Dorner (LLD), which was used to make yogurt and other cultured dairy products. The culture medium for LLD required liver extract. Shorb knew that the same liver extract was used to treat pernicious anemia (her father-in-law had died from the disease), and concluded that LLD could be developed as an assay method to identify the active compound. While at the University of Maryland she received a small grant from Merck, and in collaboration with Karl Folkers from that company, developed the LLD assay. This identified "LLD factor" as essential for the bacteria's growth.[142] Shorb, Folker and Alexander R. Todd, at the University of Cambridge, used the LLD assay to extract the anti-pernicious anemia factor from liver extracts, purify it, and name it vitamin B12.[143] In 1955, Todd helped elucidate the structure of the vitamin. The complete chemical structure of the molecule was determined by Dorothy Hodgkin based on crystallographic data and published in 1955[144] and 1956,[145] for which, and for other crystallographic analyses, she was awarded the Nobel Prize in Chemistry in 1964.[146] Hodgkin went on to decipher the structure of insulin.[146]
George Whipple, George Minot and William Murphy were awarded the Nobel Prize in 1934 for their work on the vitamin. Three other Nobel laureates, Alexander R. Todd (1957), Dorothy Hodgkin (1964) and Robert Burns Woodward (1965) made important contributions to its study.[147]
Nobel laureates for discoveries relating to vitamin B12
George Whipple
George Whipple
George Minot
George Minot
William P. Murphy
William P. Murphy
Alexander R. Todd
Alexander R. Todd
Dorothy Hodgkin
Dorothy Hodgkin
Robert Burns Woodward
Robert Burns Woodward
Commercial production
Industrial production of vitamin B12 is achieved through fermentation of selected microorganisms.[130] As noted above, the completely synthetic laboratory synthesis of B12 was achieved by Robert Burns Woodward and Albert Eschenmoser in 1972, though this process has no commercial potential, requiring more than 70 steps and having a yield well below 0.01%.[138]
Society and culture
In the 1970s, John A. Myers, a physician residing in Baltimore, developed a program of injecting vitamins and minerals intravenously for various medical conditions. The formula included 1000 μg of cyanocobalamin. This came to be known as the Myers' cocktail. After his death in 1984, other physicians and naturopaths took up prescribing "intravenous micro-nutrient therapy" with unsubstantiated health claims for treating fatigue, low energy, stress, anxiety, migraine, depression, immunocompromised, promoting weight loss and more.[148] However, other than a report on case studies[148] there are no benefits confirmed in the scientific literature.[149] Healthcare practitioners at clinics and spas prescribe versions of these intravenous combination products, but also intramuscular injections of just vitamin B12. A Mayo Clinic review concluded that there is no solid evidence that vitamin B12 injections provide an energy boost or aid weight loss.[150]
There is evidence that for elderly people, physicians often repeatedly prescribe and administer cyanocobalamin injections inappropriately, evidenced by the majority of subjects in one large study either having had normal serum concentrations or had not been tested prior to the injections.[
Dorothy Mary Crowfoot Hodgkin OM FRS HonFRSC[10][11] (née Crowfoot; 12 May 1910 – 29 July 1994) was a Nobel Prize-winning English chemist who advanced the technique of X-ray crystallography to determine the structure of biomolecules, which became essential for structural biology.[10][12]
Among her most influential discoveries are the confirmation of the structure of penicillin as previously surmised by Edward Abraham and Ernst Boris Chain; and mapping the structure of vitamin B12, for which in 1964 she became the third woman to win the Nobel Prize in Chemistry. Hodgkin also elucidated the structure of insulin in 1969 after 35 years of work.[13]
Hodgkin used the name "Dorothy Crowfoot" until twelve years after marrying Thomas Lionel Hodgkin, when she began using "Dorothy Crowfoot Hodgkin". Hodgkin is referred to as "Dorothy Hodgkin" by the Royal Society (when referring to its sponsorship of the Dorothy Hodgkin fellowship), and by Somerville College. The National Archives of the United Kingdom refer to her as "Dorothy Mary Crowfoot Hodgkin".
Early life
Dorothy Mary Crowfoot was born in Cairo, Egypt,[14] the oldest of the four daughters whose parents worked in North Africa and the middle East in the colonial administration and later as archaeologists. Dorothy came from a distinguished family of archaeologists.[15] Her parents were John Winter Crowfoot (1873–1959), working for the country's Ministry of Education, and his wife Grace Mary (née Hood) (1877–1957), known to friends and family as Molly.[16] The family lived in Cairo during the winter months, returning to England each year to avoid the hotter part of the season in Egypt.[17]
In 1914, Hodgkin's mother left her (age 4) and her two younger sisters Joan (age 2) and Elisabeth (age 7 months) with their Crowfoot grandparents near Worthing, and returned to her husband in Egypt. They spent much of their childhood apart from their parents, yet they were supportive from afar. Her mother would encourage Dorothy to pursue the interest in crystals first displayed at the age of 10. In 1923, Dorothy and her sister would study pebbles that they had found nearby streams using portable mineral analysis kit. Their parents then moved south to Sudan where, until 1926, her father was in charge of education and archaeology. Her mother's four brothers were killed in World War I and as a result she became an ardent supporter of the new League of Nations.[18][19]
In 1921 Hodgkin's father entered her in the Sir John Leman Grammar School in Beccles, England,[11] where she was one of two girls allowed to study chemistry.[20] Only once, when she was 13, did she make an extended visit to her parents, then living in Khartoum, the capital of Sudan, where her father was Principal of Gordon College. When she was 14, her distant cousin, the chemist Charles Harington (later Sir Charles), recommended D. S. Parsons' Fundamentals of Biochemistry.[21] Resuming the pre-war pattern, her parents lived and worked abroad for part of the year, returning to England and their children for several months every summer. In 1926, on his retirement from the Sudan Civil Service, her father took the post of Director of the British School of Archaeology in Jerusalem, where he and her mother remained until 1935.[22]
In 1928, Hodgkin joined her parents at the archaeological site of Jerash, in present-day Jordan, where she documented the patterns of mosaics from multiple Byzantine-era Churches dated to the 5th–6th centuries. She spent more than a year finishing the drawings as she started her studies in Oxford, while also conducting chemical analyses of glass tesserae from the same site.[23] Her attention to detail through the creation of precise scale drawings of these mosaics mirrors her subsequent work in recognising and documenting patterns in chemistry. Hodgkin enjoyed the experience of field archaeology so much that she considered giving up chemistry in favour of archaeology.[24] Her drawings are archived by Yale University.[15]
Hodgkin developed a passion for chemistry from a young age, and her mother, a proficient botanist, fostered her interest in the sciences. On her 16th birthday her mother gave her a book by W. H. Bragg on X-ray crystallography, "Concerning the Nature of Things", which helped her decide her future.[25] She was further encouraged by the chemist A.F. Joseph, a family friend who also worked in Sudan.[26]
Her state school education did not include Latin, then required for entrance to Oxbridge. Her Leman School headmaster gave her personal tuition in the subject, enabling her to pass the University of Oxford entrance examination.[citation needed]
When Hodgkin was asked in later life to name her childhood heroes, she named three women: first and foremost, her mother, Molly; the medical missionary Mary Slessor; and Margery Fry, the Principal of Somerville College.[27]
Higher education
In 1928 at age 18 Hodgkin entered Somerville College, Oxford, where she studied chemistry.[26] She graduated in 1932 with a first-class honours degree, the third woman at this institution to achieve this distinction.[28]
Dorothy Hodgkin as Chancellor of the University of Bristol
In the autumn of that year, she began studying for a PhD at Newnham College, Cambridge, under the supervision of John Desmond Bernal.[29] It was then that she became aware of the potential of X-ray crystallography to determine the structure of proteins. She was working with Bernal on the technique's first application to the analysis of a biological substance, pepsin.[30] The pepsin experiment is largely credited to Hodgkin, however she always made it clear that it was Bernal who initially took the photographs and gave her additional key insights.[31] Her PhD was awarded in 1937 for research on X-ray crystallography and the chemistry of sterols.[2]
Career and discoveries
A three dimensional contour map of the electron density of penicillin derived from x-ray diffraction. The points of highest density show the positions of individual atoms in the penicillin. This device was used by Hodgkin to deduce the structure.
Molecular model of penicillin built by Hodgkin using the electron density contour maps behind the model.
Molecular structure of vitamin B12, as established by Hodgkin
In 1933 Hodgkin was awarded a research fellowship by Somerville College, and in 1934, she moved back to Oxford. She started teaching chemistry with her own lab equipment. The college appointed her its first fellow and tutor in chemistry in 1936, a post which she held until 1977. In the 1940s, one of her students was Margaret Roberts (later Margaret Thatcher)[32] who, while Prime Minister, hung a portrait of Hodgkin in her office at Downing Street out of respect for her former teacher.[26] Hodgkin was, however a life-long Labour Party supporter.[33]
In April 1953, together with Sydney Brenner, Jack Dunitz, Leslie Orgel, and Beryl M. Oughton, Hodgkin was one of the first people to travel from Oxford to Cambridge to see the model of the double helix structure of DNA, constructed by Francis Crick and James Watson, which was based on data and technique acquired by Maurice Wilkins and Rosalind Franklin. According to the late Dr Beryl Oughton (married name, Rimmer), they drove to Cambridge in two cars after Hodgkin announced that they were off to see the model of the structure of DNA.
Hodgkin became a reader at Oxford in 1957 and she was given a fully modern laboratory the following year.[34] In 1960, Hodgkin was appointed the Royal Society's Wolfson Research Professor, a position she held until 1970.[35] This provided her salary, research expenses and research assistance to continue her work at the University of Oxford. She was a fellow of Wolfson College, Oxford, from 1977 to 1983.[36]
Steroid structure
Hodgkin was particularly noted for discovering three-dimensional biomolecular structures.[12] In 1945, working with C.H. (Harry) Carlisle, she published the first such structure of a steroid, cholesteryl iodide (having worked with cholesteryls since the days of her doctoral studies).[37]
Penicillin structure
In 1945, Hodgkin and her colleagues, including biochemist Barbara Low, solved the structure of penicillin, demonstrating, contrary to scientific opinion at the time, that it contains a β-lactam ring. The work was not published until 1949.[38][nb 1]
Vitamin B12 structure
In 1948, Hodgkin first encountered vitamin B12,[39] one of the most structurally complex vitamins known, and created new crystals. Vitamin B12 had first been discovered at Merck earlier that year. It had a structure at the time that was almost completely unknown, and when Hodgkin discovered it contained cobalt, she realized the structure actualization could be determined by X-ray crystallography analysis. The large size of the molecule, and the fact that the atoms were largely unaccounted for—aside from cobalt—posed a challenge in structure analysis that had not been previously explored.[40]
F
2014 – Maryam Mirzakhani (12 May 1977 – 14 July 2017), the first woman to have won the prize, was an Iranian mathematician and a professor of mathematics at Stanford University.
2022 – Maryna Viazovska[132]
Statistics
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The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. You may improve this section, discuss the issue on the talk page, or create a new section, as appropriate. (April 2013) (Learn how and when to remove this message)
Statistics are used to indicate disadvantages faced by women in science, and also to track positive changes of employment opportunities and incomes for women in science.[110]: 33
Situation in the 1990s
Women appear to do less well than men (in terms of degree, rank, and salary) in the fields that have been traditionally dominated by women, such as nursing. In 1991 women attributed 91% of the PhDs in nursing, and men held 4% of full professorships in nursing.[citation needed] In the field of psychology, where women earn the majority of PhDs, women do not fill the majority of high rank positions in that field.[133][citation needed]
Women's lower salaries in the scientific community are also reflected in statistics. According to the data provided in 1993, the median salaries of female scientists and engineers with doctoral degrees were 20% less than men.[110]: 35 [needs update] This data can be explained[who?] as there was less participation of women in high rank scientific fields/positions and a female majority in low-paid fields/positions. However, even with men and women in the same scientific community field, women are typically paid 15–17% less than men.[citation needed] In addition to the gender gap, there were also salary differences between ethnicity: African-American women with more years of experiences earn 3.4% less than European-American women with similar skills, while Asian women engineers out-earn both Africans and Europeans.[134][needs update]
Women are also under-represented in the sciences as compared to their numbers in the overall working population. Within 11% of African-American women in the workforce, 3% are employed as scientists and engineers.[clarification needed] Hispanics made up 8% of the total workers in the US, 3% of that number are scientists and engineers. Native Americans participation cannot be statistically measured.[citation needed]
Women tend to earn less than men in almost all industries, including government and academia.[citation needed] Women are less likely to be hired in highest-paid positions.[citation needed] The data showing the differences in salaries, ranks, and overall success between the genders is often claimed[who?] to be a result of women's lack of professional experience. The rate of women's professional achievement is increasing. In 1996, the salaries for women in professional fields increased from 85% to 95% relative to men with similar skills and jobs. Young women between the age of 27 and 33 earned 98%, nearly as much as their male peers.[needs update] In the total workforce of the United States, women earn 74% as much as their male counterparts (in the 1970s they made 59% as much as their male counterparts).[110]: 33–37 [needs update]
Claudia Goldin, Harvard concludes in A Grand Gender Convergence: Its Last Chapter – "The gender gap in pay would be considerably reduced and might vanish altogether if firms did not have an incentive to disproportionately reward individuals who labored long hours and worked particular hours."[135]
Research on women's participation in the "hard" sciences such as physics and computer science speaks of the "leaky pipeline" model, in which the proportion of women "on track" to potentially becoming top scientists fall off at every step of the way, from getting interested in science and maths in elementary school, through doctorate, postdoctoral, and career steps. The leaky pipeline also applies in other fields. In biology, for instance, women in the United States have been getting Masters degrees in the same numbers as men for two decades, yet fewer women get PhDs; and the numbers of women principal investigators have not risen.[136]
What may be the cause of this "leaky pipeline" of women in the sciences?[tone] It is important to look at factors outside of academia that are occurring in women's lives at the same time they are pursuing their continued education and career search. The most outstanding factor that is occurring at this crucial time is family formation. As women are continuing their academic careers, they are also stepping into their new role as a wife and mother. These traditionally require at large time commitment and presence outside work. These new commitments do not fare well for the person looking to attain tenure. That is why women entering the family formation period of their life are 35% less likely to pursue tenure positions after receiving their PhD's than their male counterparts.[137]
In the UK, women occupied over half the places in science-related higher education courses (science, medicine, maths, computer science and engineering) in 2004–5.[138] However, gender differences varied from subject to subject: women substantially outnumbered men in biology and medicine, especially nursing, while men predominated in maths, physical sciences, computer science and engineering.
In the US, women with science or engineering doctoral degrees were predominantly employed in the education sector in 2001, with substantially fewer employed in business or industry than men.[139] According to salary figures reported in 1991, women earn anywhere between 83.6 percent to 87.5 percent that of a man's salary.[needs update] An even greater disparity between men and women is the ongoing trend that women scientists with more experience are not as well-compensated as their male counterparts. The salary of a male engineer continues to experience growth as he gains experience whereas the female engineer sees her salary reach a plateau.[140]
Women, in the United States and many European countries, who succeed in science tend to be graduates of single-sex schools.[110]: Chapter 3 [needs update] Women earn 54% of all bachelor's degrees in the United States and 50% of those are in science. 9% of US physicists are women.[110]: Chapter 2 [needs update]
Overview of situation in 2013
The leaky pipeline, share of women in higher education and research worldwide, 2013. Source: UNESCO Science Report: towards 2030, Figure 3.3, data from UNESCO Institute for Statistics.
In 2013, women accounted for 53% of the world's graduates at the bachelor's and master's level and 43% of successful PhD candidates but just 28% of researchers. Women graduates are consistently highly represented in the life sciences, often at over 50%. However, their representation in the other fields is inconsistent. In North America and much of Europe, few women graduate in physics, mathematics and computer science but, in other regions, the proportion of women may be close to parity in physics or mathematics. In engineering and computer sciences, women consistently trail men, a situation that is particularly acute in many high-income countries.[141]
Share of women in selected South African institutions in 2011. Source: UNESCO Science Report: towards 2030, based on a 2011 study by the Academy of Sciences of South Africa on the Participation of Girls and Women in the National STI System in South Africa.
In decision-making
As of 2015, each step up the ladder of the scientific research system saw a drop in female participation until, at the highest echelons of scientific research and decision-making, there were very few women left. In 2015, the EU Commissioner for Research, Science and Innovation Carlos Moedas called attention to this phenomenon, adding that the majority of entrepreneurs in science and engineering tended to be men. In 2013, the German government coalition agreement introduced a 30% quota for women on company boards of directors.[141]
In 2010, women made up 14% of university chancellors and vice-chancellors at Brazilian public universities and 17% of those in South Africa in 2011.[142][143] As of 2015, in Argentina, women made up 16% of directors and vice-directors of national research centres and, in Mexico, 10% of directors of scientific research institutes at the National Autonomous University of Mexico.[144][145] In the US, numbers are slightly higher at 23%. In the EU, less than 16% of tertiary institutions were headed by a woman in 2010 and just 10% of universities. In 2011, at the main tertiary institution for the English-speaking Caribbean, the University of the West Indies, women represented 51% of lecturers but only 32% of senior lecturers and 26% of full professors . A 2018 review of the Royal Society of Britain by historians Aileen Fyfe and Camilla Mørk Røstvik produced similarly low numbers,[146] with women accounting for more than 25% of members in only a handful of countries, including Cuba, Panama and South Africa. As of 2015, the figure for Indonesia was 17%.[141][147][148]
Women in life sciences
In life sciences, women researchers have achieved parity (45–55% of researchers) in many countries. In some, the balance even now tips in their favour. Six out of ten researchers are women in both medical and agricultural sciences in Belarus and New Zealand, for instance. More than two-thirds of researchers in medical sciences are women in El Salvador, Estonia, Kazakhstan, Latvia, the Philippines, Tajikistan, Ukraine and Venezuela.[141]
There has been a steady increase in female graduates in agricultural sciences since the turn of the century. In sub-Saharan Africa, for instance, numbers of female graduates in agricultural science have been increasing steadily, with eight countries reporting a share of women graduates of 40% or more: Lesotho, Madagascar, Mozambique, Namibia, Sierra Leone, South Africa, Swaziland and Zimbabwe. The reasons for this surge are unclear, although one explanation may lie in the growing emphasis on national food security and the food industry. Another possible explanation is that women are highly represented in biotechnology. For example, in South Africa, women were underrepresented in engineering (16%) in 2004 and in 'natural scientific professions' (16%) in 2006 but made up 52% of employees working in biotechnology-related companies.[141]
Women play an increasing role in environmental sciences and conservation biology. In fact, women played a foremost role in the development of these disciplines. Silent Spring by Rachel Carson proved an important impetus to the conservation movement and the later banning of chemical pesticides. Women played an important role in conservation biology including the famous work of Dian Fossey, who published the famous Gorillas in the Mist and Jane Goodall who studied primates in East Africa. Today women make up an increasing proportion of roles in the active conservation sector. A recent survey of those working in the Wildlife Trusts in the U.K., the leading conservation organisation in England, found that there are nearly as many women as men in practical conservation roles.[149]
In engineering and related fields
Women are consistently underrepresented in engineering and related fields. In Israel, for instance, where 28% of senior academic staff are women, there are proportionately many fewer in engineering (14%), physical sciences (11%), mathematics and computer sciences (10%) but dominate education (52%) and paramedical occupations (63%). In Japan and the Republic of Korea, women represent just 5% and 10% of engineers.[141]
For women who are pursuing STEM major careers, these individuals often face gender disparities in the work field, especially in regards to science and engineering. It has become more common for women to pursue undergraduate degrees in science, but are continuously discredited in salary rates and higher ranking positions. For example, men show a greater likelihood of being selected for an employment position than a woman.[150]
In Europe and North America, the number of female graduates in engineering, physics, mathematics and computer science is generally low. Women make up just 19% of engineers in Canada
In many cases, engineering has lost ground to other sciences, including agriculture. The case of New Zealand is fairly typical. Here, women jumped from representing 39% to 70% of agricultural graduates between 2000 and 2012, continued to dominate health (80–78%) but ceded ground in science (43–39%) and engineering (33–27%).[141]
In a number of developing countries, there is a sizable proportion of women engineers. At least three out of ten engineers are women, for instance, in Costa Rica, Vietnam and the United Arab Emirates (31%), Algeria (32%), Mozambique (34%), Tunisia (41%) and Brunei Darussalam (42%). In Malaysia (50%) and Oman (53%), women are on a par with men. Of the 13 sub-Saharan countries reporting data, seven have observed substantial increases (more than 5%) in women engineers since 2000, namely: Benin, Burundi, Eritrea, Ethiopia, Madagascar, Mozambique and Namibia.[141]
Of the seven Arab countries reporting data, four observe a steady percentage or an increase in female engineers (Morocco, Oman, Palestine and Saudi Arabia). In the United Arab Emirates, the government has made it a priority to develop a knowledge economy, having recognized the need for a strong human resource base in science, technology and engineering. With just 1% of the labour force being Emirati, it is also concerned about the low percentage of Emirati citizens employed in key industries. As a result, it has introduced policies promoting the training and employment of Emirati citizens, as well as a greater participation of Emirati women in the labour force. Emirati female engineering students have said that they are attracted to a career in engineering for reasons of financial independence, the high social status associated with this field, the opportunity to engage in creative and challenging projects and the wide range of career opportunities.[141]
An analysis of computer science shows a steady decrease in female graduates since 2000 that is particularly marked in high-income countries. Between 2000 and 2012, the share of women graduates in computer science slipped in Australia, New Zealand, the Republic of Korea and USA. In Latin America and the Caribbean, the share of women graduates in computer science dropped by between 2 and 13 percentage points over this period for all countries reporting data.[141]
There are exceptions. In Denmark, the proportion of female graduates in computer science increased from 15% to 24% between 2000 and 2012 and Germany saw an increase from 10% to 17%. These are still very low levels. Figures are higher in many emerging economies. In Turkey, for instance, the proportion of women graduating in computer science rose from a relatively high 29% to 33% between 2000 and 2012.[141]
The Malaysian information technology (IT) sector is made up equally of women and men, with large numbers of women employed as university professors and in the private sector. This is a product of two historical trends: the predominance of women in the Malay electronics industry, the precursor to the IT industry, and the national push to achieve a 'pan-Malayan' culture beyond the three ethnic groups of Indian, Chinese and Malay. Government support for the education of all three groups is available on a quota basis and, since few Malay men are interested in IT, this leaves more room for women. Additionally, families tend to be supportive of their daughters' entry into this prestigious and highly remunerated industry, in the interests of upward social mobility. Malaysia's push to develop an endogenous research culture should deepen this trend.[141]
In India, the substantial increase in women undergraduates in engineering may be indicative of a change in the 'masculine' perception of engineering in the country. It is also a product of interest on the part of parents, since their daughters will be assured of employment as the field expands, as well as an advantageous marriage. Other factors include the 'friendly' image of engineering in India and the easy access to engineering education resulting from the increase in the number of women's engineering colleges over the last two decades.[141]
In space
While women have made huge strides in the STEM fields, it is obvious that they are still underrepresented. One of the areas where women are most underrepresented in science is space flight. Out of the 556 people who have traveled to space, only 65 of them were women. This means that only 11% of astronauts have been women.[151]
In the 1960s, the American space program was taking off. However, women were not allowed to be considered for the space program because at the time astronauts were required to be military pilots—a profession that women were not allowed to be a part of. There were other "practical" reasons as well. According to General Don Flickinger of the United States Air Force, there was difficulty "designing and fitting a space suit to accommodate their particular biological needs and functions."[152]
During the early 1960s, the first American astronauts, nicknamed the Mercury Seven, were training. At the same time, William Randolph Lovelace II was interested to see if women could manage to go through the same training that the Mercury 7 undergoing at the time. Lovelace recruited thirteen female pilots, called the "Mercury 13", and put them through the same tests that the male astronauts took. As a result, the women actually performed better on these tests than the men of the Mercury 7 did. However, this did not convince NASA officials to allow women in space.[151] In response, congressional hearings were held to investigate discrimination against women in the program. One of the women who testified at the hearing was Jerrie Cobb, the first woman to pass Lovelace's tests.[153] During her testimony, Cobb said:[151]
I find it a little ridiculous when I read in a newspaper that there is a place called Chimp College in New Mexico where they are training chimpanzees for space flight, one a female named Glenda. I think it would be at least as important to let the women undergo this training for space flight.
NASA officials also had representatives present, notably astronauts John Glenn and Scott Carpenter, to testify that women are not suited for the space program. Ultimately, no action came from the hearings, and NASA did not put a woman in space until 1983.[153]
Even though the United States did not allow women in space during the 60s or 70s, other countries did. Valentina Tereshkova, a cosmonaut from the Soviet Union, was the first woman to fly in space. Although she had no piloting experience, she flew on the Vostok 6 in 1963. Before going to space, Tereshkova was a textile worker. Although she successfully orbited the Earth 48 times, the next woman to go to space did not fly until almost twenty years later.[154]
Sally Ride was the third woman to go to space and the first American woman in space. In 1978, Ride and five other women were accepted into the first class of astronauts that allowed women. In 1983, Ride became the first American woman in space when she flew on the Challenger for the STS-7 mission.[154]
NASA has been more inclusive in recent years. The number of women in NASA's astronaut classes has steadily risen since the first class that allowed women in 1978. The most recent class was 45% women, and the class before was 50%. In 2019, the first all-female spacewalk was completed at the International Space Station.[155]
Share of female researchers by country, 2013 or closest year. Source: UNESCO Science Report: towards 2030, data from UNESCO Institute for Statistics.
Regional trends as of 2013
The global figures mask wide disparities from one region to another. In Southeast Europe, for instance, women researchers have obtained parity and, at 44%, are on the verge of doing so in Central Asia and Latin America and the Caribbean. In the European Union, on the other hand, just one in three (33%) researchers is a woman, compared to 37% in the Arab world. Women are also better represented in sub-Saharan Africa (30%) than in South Asia (17%).[141]
There are also wide intraregional disparities. Women make up 52% of researchers in the Philippines and Thailand, for instance, and are close to parity in Malaysia and Vietnam, yet only one in three researchers is a woman in Indonesia and Singapore. In Japan and the Republic of Korea, two countries characterized by high researcher densities and technological sophistication, as few as 15% and 18% of researchers respectively are women. These are the lowest ratios among members of the Organisation for Economic Co-operation and Development. The Republic of Korea also has the widest gap among OECD members in remuneration between men and women researchers (39%). There is also a yawning gap in Japan (29%).[141]
Latin America and the Caribbean
Latin America has some of the world's highest rates of women studying scientific fields; it also shares with the Caribbean one of the highest proportions of female researchers: 44%. Of the 12 countries reporting data for the years 2010–2013, seven have achieved gender parity, or even dominate research: Bolivia (63%), Venezuela (56%), Argentina (53%), Paraguay (52%), Uruguay (49%), Brazil (48%) and Guatemala (45%). Costa Rica is on the cusp (43%). Chile has the lowest score among countries for which there are recent data (31%). The Caribbean paints a similar picture, with Cuba having achieved gender parity (47%) and Trinidad and Tobago on 44%. Recent data on women's participation in industrial research are available for those countries with the most developed national innovation systems, with the exception of Brazil and Cuba: Uruguay (47%), Argentina (29%), Colombia and Chile (26%).[141]
As in most other regions, the great majority of health graduates are women (60–85%). Women are also strongly represented in science. More than 40% of science graduates are women in each of Argentina, Colombia, Ecuador, El Salvador, Mexico, Panama and Uruguay. The Caribbean paints a similar picture, with women graduates in science being on a par with men or dominating this field in Barbados, Cuba, Dominican Republic and Trinidad and Tobago.[141]
In engineering, women make up over 30% of the graduate population in seven Latin American countries (Argentina, Colombia, Costa Rica, Honduras, Panama and Uruguay) and one Caribbean country, the Dominican Republic. There has been a decrease in the number of women engineering graduates in Argentina, Chile and Honduras.[141]
The participation of women in science has consistently dropped since the turn of the century. This trend has been observed in all sectors of the larger economies: Argentina, Brazil, Chile and Colombia. Mexico is a notable exception, having recorded a slight increase. Some of the decrease may be attributed to women transferring to agricultural sciences in these countries. Another negative trend is the drop in female doctoral students and in the labour force. Of those countries reporting data, the majority signal a significant drop of 10–20 percentage points in the transition from master's to doctoral graduates.[141]
Eastern Europe, West and Central Asia
Most countries in Eastern Europe, West and Central Asia have attained gender parity in research (Armenia, Azerbaijan, Georgia, Kazakhstan, Mongolia and Ukraine) or are on the brink of doing so (Kyrgyzstan and Uzbekistan). This trend is reflected in tertiary education, with some exceptions in engineering and computer science. Although Belarus and the Russian Federation have seen a drop over the past decade, women still represented 41% of researchers in 2013. In the former Soviet states, women are also very present in the business enterprise sector: Bosnia and Herzegovina (59%), Azerbaijan (57%), Kazakhstan (50%), Mongolia (48%), Latvia (48%), Serbia (46%), Croatia and Bulgaria (43%), Ukraine and Uzbekistan (40%), Romania and Montenegro (38%), Belarus (37%), Russian Federation (37%).[141]
One in three researchers is a woman in Turkey (36%) and Tajikistan (34%). Participation rates are lower in Iran (26%) and Israel (21%), although Israeli women represent 28% of senior academic staff. At university, Israeli women dominate medical sciences (63%) but only a minority study engineering (14%), physical sciences (11%), mathematics and computer science (10%). There has been an interesting evolution in Iran. Whereas the share of female PhD graduates in health remained stable at 38–39% between 2007 and 2012, it rose in all three other broad fields. Most spectacular was the leap in female PhD graduates in agricultural sciences from 4% to 33% but there was also a marked progression in science (from 28% to 39%) and engineering (from 8% to 16%).[141]
Southeast Europe
With the exception of Greece, all the countries of Southeast Europe were once part of the Soviet bloc. Some 49% of researchers in these countries are women (compared to 37% in Greece in 2011). This high proportion is considered a legacy of the consistent investment in education by the Socialist governments in place until the early 1990s, including that of the former Yugoslavia. Moreover, the participation of female researchers is holding steady or increasing in much of the region, with representation broadly even across the four sectors of government, business, higher education and non-profit. In most countries, women tend to be on a par with men among tertiary graduates in science. Between 70% and 85% of graduates are women in health, less than 40% in agriculture and between 20% and 30% in engineering. Albania has seen a considerable increase in the share of its women graduates in engineering and agriculture.[141]
European Union
Women make up 33% of researchers overall in the European Union (EU), slightly more than their representation in science (32%). Women constitute 40% of researchers in higher education, 40% in government and 19% in the private sector, with the number of female researchers increasing faster than that of male researchers. The proportion of female researchers has been increasing over the last decade, at a faster rate than men (5.1% annually over 2002–2009 compared with 3.3% for men), which is also true for their participation among scientists and engineers (up 5.4% annually between 2002 and 2010, compared with 3.1% for men).[141]
Despite these gains, women's academic careers in Europe remain characterized by strong vertical and horizontal segregation. In 2010, although female students (55%) and graduates (59%) outnumbered male students, men outnumbered women at the PhD and graduate levels (albeit by a small margin). Further along in the research career, women represented 44% of grade C academic staff, 37% of grade B academic staff and 20% of grade A academic staff.11 These trends are intensified in science, with women making up 31% of the student population at the tertiary level to 38% of PhD students and 35% of PhD graduates. At the faculty level, they make up 32% of academic grade C personnel, 23% of grade B and 11% of grade A. The proportion of women among full professors is lowest in engineering and technology, at 7.9%. With respect to representation in science decision-making, in 2010 15.5% of higher education institutions were headed by women and 10% of universities had a female rector.[141]
Membership on science boards remained predominantly male as well, with women making up 36% of board members. The EU has engaged in a major effort to integrate female researchers and gender research into its research and innovation strategy since the mid-2000s. Increases in women's representation in all of the scientific fields overall indicates that this effort has met with some success; however, the continued lack of representation of women at the top level of faculties, management and science decision making indicate that more work needs to be done. The EU is addressing this through a gender equality strategy and crosscutting mandate in Horizon 2020, its research and innovation funding programme for 2014–2020.[141]
ustralia, New Zealand and USA
In 2013, women made up the majority of PhD graduates in fields related to health in Australia (63%), New Zealand (58%) and the United States of America (73%). The same can be said of agriculture, in New Zealand's case (73%). Women have also achieved parity in agriculture in Australia (50%) and the United States (44%). Just one in five women graduate in engineering in the latter two countries, a situation that has not changed over the past decade. In New Zealand, women jumped from constituting 39% to 70% of agricultural graduates (all levels) between 2000 and 2012 but ceded ground in science (43–39%), engineering (33–27%) and health (80–78%). As for Canada, it has not reported sex-disaggregated data for women graduates in science and engineering in recent years. Moreover, none of the four countries mentioned here have reported recent data on the share of female researchers.[141]
South Asia
South Asia is the region where women make up the smallest proportion of researchers: 17%. This is 13 percentage points below sub-Saharan Africa. Of those countries in South Asia reporting data for 2009–2013, Nepal has the lowest representation of all (in head counts), at 8% (2010), a substantial drop from 15% in 2002. In 2013, only 14% of researchers (in full-time equivalents) were women in the region's most populous country, India, down slightly from 15% in 2009. The percentage of female researchers is highest in Sri Lanka (39%), followed by Pakistan: 24% in 2009, 31% in 2013. There are no recent data available for Afghanistan or Bangladesh.[141]
Share of women among researchers employed in the business enterprise sector, 2013 or closest year. Source: UNESCO Science Report: towards 2030, Figure 3.4, data from UNESCO Institute for Statistics.
Women are most present in the private non-profit sector – they make up 60% of employees in Sri Lanka – followed by the academic sector: 30% of Pakistani and 42% of Sri Lankan female researchers. Women tend to be less present in the government sector and least likely to be employed in the business sector, accounting for 23% of employees in Sri Lanka, 11% in India and just 5% in Nepal. Women have achieved parity in science in both Sri Lanka and Bangladesh but are less likely to undertake research in engineering. They represent 17% of the research pool in Bangladesh and 29% in Sri Lanka. Many Sri Lankan women have followed the global trend of opting for a career in agricultural sciences (54%) and they have also achieved parity in health and welfare. In Bangladesh, just over 30% choose agricultural sciences and health, which goes against the global trend. Although Bangladesh still has progress to make, the share of women in each scientific field has increased steadily over the past decade.[141]
Southeast Asia
Southeast Asia presents a different picture entirely, with women basically on a par with men in some countries: they make up 52% of researchers in the Philippines and Thailand, for example. Other countries are close to parity, such as Malaysia and Vietnam, whereas Indonesia and Singapore are still around the 30% mark. Cambodia trails its neighbours at 20%. Female researchers in the region are spread fairly equally across the sectors of participation, with the exception of the private sector, where they make up 30% or less of researchers in most countries.
The proportion of women tertiary graduates reflects these trends, with high percentages of women in science in Brunei Darussalam, Malaysia, Myanmar and the Philippines (around 60%) and a low of 10% in Cambodia. Women make up the majority of graduates in health sciences, from 60% in Laos to 81% in Myanmar – Vietnam being an exception at 42%. Women graduates are on a par with men in agriculture but less present in engineering: Vietnam (31%), the Philippines (30%) and Malaysia (39%); here, the exception is Myanmar, at 65%. In the Republic of Korea, women make up about 40% of graduates in science and agriculture and 71% of graduates in health sciences but only 18% of female researchers overall. This represents a loss in the investment made in educating girls and women up through tertiary education, a result of traditional views of women's role in society and in the home. Kim and Moon (2011) remark on the tendency of Korean women to withdraw from the labour force to take care of children and assume family responsibilities, calling it a 'domestic brain drain'.[141]
Women remain very much a minority in Japanese science (15% in 2013), although the situation has improved slightly (13% in 2008) since the government fixed a target in 2006 of raising the ratio of female researchers to 25%. Calculated on the basis of the current number of doctoral students, the government hopes to obtain a 20% share of women in science, 15% in engineering and 30% in agriculture and health by the end of the current Basic Plan for Science and Technology in 2016. In 2013, Japanese female researchers were most common in the public sector in health and agriculture, where they represented 29% of academics and 20% of government researchers. In the business sector, just 8% of researchers were women (in head counts), compared to 25% in the academic sector. In other public research institutions, women accounted for 16% of researchers. One of the main thrusts of Abenomics, Japan's current growth strategy, is to enhance the socio-economic role of women. Consequently, the selection criteria for most large university grants now take into account the proportion of women among teaching staff and researchers.[141]
The low ratio of women researchers in Japan and the Republic of Korea, which both have some of the highest researcher densities in the world, brings down Southeast Asia's average to 22.5% for the share of women among researchers in the region.[141]
Arab States
At 37%, the share of female researchers in the Arab States compares well with other regions. The countries with the highest proportion of female researchers are Bahrain and Sudan at around 40%. Jordan, Libya, Oman, Palestine and Qatar have percentage shares in the low twenties. The country with the lowest participation of female researchers is Saudi Arabia, even though they make up the majority of tertiary graduates, but the figure of 1.4% covers only the King Abdulaziz City for Science and Technology. Female researchers in the region are primarily employed in government research institutes, with some countries also seeing a high participation of women in private nonprofit organizations and universities.[156] With the exception of Sudan (40%) and Palestine (35%), fewer than one in four researchers in the business enterprise sector is a woman; for half of the countries reporting data, there are barely any women at all employed in this sector.[141]
Despite these variable numbers, the percentage of female tertiary-level graduates in science and engineering is very high across the region, which indicates there is a substantial drop between graduation and employment and research. Women make up half or more than half of science graduates in all but Sudan and over 45% in agriculture in eight out of the 15 countries reporting data, namely Algeria, Egypt, Jordan, Lebanon, Sudan, Syria, Tunisia and the United Arab Emirates. In engineering, women make up over 70% of graduates in Oman, with rates of 25–38% in the majority of the other countries, which is high in comparison to other regions.[141]
The participation of women is somewhat lower in health than in other regions, possibly on account of cultural norms restricting interactions between males and females. Iraq and Oman have the lowest percentages (mid-30s), whereas Iran, Jordan, Kuwait, Palestine and Saudi Arabia are at gender parity in this field. The United Arab Emirates and Bahrain have the highest rates of all: 83% and 84%.[141]
Once Arab women scientists and engineers graduate, they may come up against barriers to finding gainful employment. These include a misalignment between university programmes and labour market demand – a phenomenon which also affects men –, a lack of awareness about what a career in their chosen field entails, family bias against working in mixed-gender environments and a lack of female role models.[141][157]
One of the countries with the smallest female labour force is developing technical and vocational education for girls as part of a wider scheme to reduce dependence on foreign labour. By 2017, the Technical and Vocational Training Corporation of Saudi Arabia is to have constructed 50 technical colleges, 50 girls' higher technical institutes and 180 industrial secondary institutes. The plan is to create training placements for about 500 000 students, half of them girls. Boys and girls will be trained in vocational professions that include information technology, medical equipment handling, plumbing, electricity and mechanics.[141]
Sub-Saharan Africa
Just under one in three (30%) researchers in sub-Saharan Africa is a woman. Much of sub-Saharan Africa is seeing solid gains in the share of women among tertiary graduates in scientific fields. In two of the top four countries for women's representation in science, women graduates are part of very small cohorts, however: they make up 54% of Lesotho's 47 tertiary graduates in science and 60% of those in Namibia's graduating class of 149. South Africa and Zimbabwe, which have larger graduate populations in science, have achieved parity, with 49% and 47% respectively. The next grouping clusters seven countries poised at around 35–40% (Angola, Burundi, Eritrea, Liberia, Madagascar, Mozambique and Rwanda). The rest are grouped around 30% or below (Benin, Ethiopia, Ghana, Swaziland and Uganda). Burkina Faso ranks lowest, with women making up 18% of its science graduates.[141]
Female representation in engineering is fairly high in sub-Saharan Africa in comparison with other regions. In Mozambique and South Africa, for instance, women make up more than 34% and 28% of engineering graduates, respectively. Numbers of female graduates in agricultural science have been increasing steadily across the continent, with eight countries reporting the share of women graduates of 40% or more (Lesotho, Madagascar, Mozambique, Namibia, Sierra Leone, South Africa, Swaziland and Zimbabwe). In health, this rate ranges from 26% and 27% in Benin and Eritrea to 94% in Namibia.[141]
Of note is that women account for a relatively high proportion of researchers employed in the business enterprise sector in South Africa (35%), Kenya (34%), Botswana and Namibia (33%) and Zambia (31%). Female participation in industrial research is lower in Uganda (21%), Ethiopia (15%) and Mali (12%).[141]
Lack of agency and representation
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Social pressures to both conform to femininity and which punish femininity
Beginning in the twentieth century[original research?] to present day, more and more women are becoming acknowledged for their work in science. However, women often find themselves at odds with expectations held towards them in relation to their scientific studies. For example, in 1968 James Watson questioned scientist Rosalind Franklin's place in the industry. He claimed that "the best place for a feminist was in another person's lab",[110]: 76–77 most often a male's research lab.[improper synthesis?] Women were and still are often critiqued of their overall presentation.[citation needed] In Franklin's situation, she was seen as lacking femininity for she failed to wear lipstick or revealing clothing.[110]: 76–77
Since on average most of a woman's colleagues in science are men who do not see her as a true social peer, she will also find herself left out of opportunities to discuss possible research opportunities outside of the laboratory. In Londa Schiebinger's book, Has Feminism Changed Science?, she mentions that men would have discussed their research outside of the lab, but this conversation is preceded by culturally "masculine" small-talk topics that, whether intentionally or not, excluded women influenced by their culture's feminine gender role from the conversation.[110]: 81–91 Consequently, this act of excluding many women from the after-hours work discussions produced a more separate work environment between the men and the women in science; as women then would converse with other women in science about their current findings and theories. Ultimately, the women's work was devalued as a male scientist was not involved in the overall research and analysis.
According to Oxford University Press, the inequality toward women is "endorsed within cultures and entrenched within institutions [that] hold power to reproduce that inequality".[158] There are various gendered barriers in social networks that prevent women from working in male-dominated fields and top management jobs. Social networks are based on the cultural beliefs such as schemas and stereotypes.[158] According to social psychology studies, top management jobs are more likely to have incumbent schemas that favor "an achievement-oriented aggressiveness and emotional toughness that is distinctly male in character".[158] Gender stereotypes of feminine style set by men assume women to be conforming and submissive to male culture creating a sense of unqualified women for top management jobs. However, when the women try to prove their competence and power, they often faced obstacles. They are likely to be seen as dislikable and untrustworthy even when they excel at "masculine" tasks.[158] In addition, women's achievements are likely to be dismissed or discredited.[158] These "untrustworthy, dislikable women" could have very well been denied achievement from the fear men held of a woman overtaking his management position. Social networks and gender stereotypes produce many injustices that women have to experience in their workplace, as well as, the various obstacles they encounter when trying to advance in male-dominated and top management jobs. Women in professions like science, technology, and other related industries are likely to encounter these gendered barriers in their careers.[158] Based on the meritocratic explanations of gender inequality, "as long as the people accept the mechanisms that produce unequal outcomes", all the outcomes will be legitimated in the society.[158] When women try to deny the stereotypes and the discriminations by becoming "competent, integrated, well-liked", the society is more likely to look at these impressions as selfishness or "being a whiner".[158] However, there have been positive attempts to reduce gender discrimination in the public domain. For example, in the United States, Title IX of the Education Amendments of 1972 provides opportunities for women to achieve to a wide range of education programs and activities by prohibiting sex discrimination.[159] The law states "No person in the United States shall, on the basis of sex, be excluded from participation in, be denied the benefits of, or be subject to discrimination under any educational program or activity receiving federal financial assistance."[159] Although, even with laws prohibiting gender discrimination, society and social institutions continue to minimize women's competencies and accomplishments, especially, in the workforce by dismissing or discrediting their achievements as stated above.
Underrepresentation of homosexual and bi women, and gender nonconformists in STEM
While there has been a push to encourage more women to participate in science, there is less outreach to lesbian, bi, or gender nonconforming women, and gender nonconforming people more broadly.[160] Due to the lack of data and statistics of LGBTQ members involvement in the STEM field, it is unknown to what exact degree lesbian and bisexual women, gender non-conformers (transgender, nonbinary/agender, or anti-gender gender abolitionists who eschew the system altogether) are potentially even more repressed and underrepresented than their straight peers. But a general lack of out lesbian and bi women in STEM has been noted.[160][161] Reasons for under-representation of same-sex attracted women and anyone gender nonconforming in STEM fields include lack of role models in K–12,[160][161][162] the desire of some transgender girls and women to adopt traditional heteronormative gender roles as gender is a cultural performance and socially-determined subjective internal experience,[163][164] employment discrimination, and the possibility of sexual harassment in the workplace. Historically, women who have accepted STEM research positions for the government or the military remained in the closet due to lack of federal protections or the fact that homosexual or gender nonconforming expression was criminalized in their country. A notable example is Sally Ride, a physicist, the first American female astronaut, and a lesbian.[165][166] Sally Ride chose not to reveal her sexuality until after her death in 2012; she purposefully revealed her sexual orientation in her obituary.[166] She has been known as the first female (and youngest) American to enter space, as well as, starting her own company, Sally Ride Science, that encourages young girls to enter the STEM field. She chose to keep her sexuality to herself because she was familiar with "the male-dominated" NASA's anti-homosexual policies at the time of her space travel.[166] Sally Ride's legacy continues as her company is still working to increase young girls and women's participation in the STEM fields.[167]
In a nationwide study of LGBTQA employees in STEM fields in the United States, same-sex attracted and gender nonconforming women in engineering, earth sciences, and mathematics reported that they were less likely to be out in the workplace.[168] In general, LGBTQA people in this survey reported that, when more female or feminine gender role-identified people worked in their labs, the more accepting and safe the work environment.[168] In another study of over 30,000 LGBT employees in STEM-related federal agencies in the United States, queer women in these agencies reported feeling isolated in the workplace and having to work harder than their gender conforming male colleagues. This isolation and overachievement remained constant as they earned supervisory positions and worked their way up the ladder.[169] Gender nonconforming people in physics, particularly those identified as trans women in physics programs and labs, felt the most isolated and perceived the most hostility.[170]
Organizations such as Lesbians Who Tech, National Organization of Gay and Lesbian Scientists and Technical Professionals (NOGLSTP), Out in Science, Technology, Engineering and Mathematics (OSTEM), Pride in STEM, and House of STEM currently provide networking and mentoring opportunities for lesbian girls and women and LGBT people interested in or currently working in STEM fields. These organizations also advocate for the rights of lesbian and bi women and gender nonconformists in STEM in education and the workplace.
Reasons for disadvantages
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Margaret Rossiter, an American historian of science, offered three concepts to explain the reasons behind the data in statistics and how these reasons disadvantaged women in the science industry. The first concept is hierarchical segregation.[171] This is a well-known phenomenon in society, that the higher the level and rank of power and prestige, the smaller the population of females participating. The hierarchical differences point out that there are fewer women participating at higher levels of both academia and industry. Based on data collected in 1982, women earn 54 percent of all bachelor's degrees in the United States, with 50 percent of these in science. The source also indicated that this number increased almost every year.[172] There are fewer women at the graduate level; they earn 40 percent of all doctorates, with 31 percent of these in science and engineering.
The second concept included in Rossiter's explanation of women in science is territorial segregation.[110]: 34–35 The term refers to how female employment is often clustered in specific industries or categories in industries. Women stayed at home or took employment in feminine fields while men left the home to work. Although nearly half of the civilian work force is female, women still comprise the majority of low-paid jobs or jobs that society considered feminine. Statistics show that 60 percent of white professional women are nurses, daycare workers, or schoolteachers.[173] Territorial disparities in science are often found between the 1920s and 1930s, when different fields in science were divided between men and women.
Researchers collected the data on many differences between women and men in science. Rossiter found that in 1966, thirty-eight percent of female scientists held master's degrees compared to twenty-six percent of male scientists; but large proportions of female scientists were in environmental and nonprofit organizations.[174] During the late 1960s and 1970s, equal-rights legislation made the number of female scientists rise dramatically. The statistics from National Science Board (NSB) present the change at that time.[citation needed] The number of science degrees awarded to woman rose from seven percent in 1970 to twenty-four percent in 1985. In 1975 only 385 women received bachelor's degrees in engineering compared to 11,000 women in 1985. Elizabeth Finkel claims that even if the number of women participating in scientific fields increases, the opportunities are still limited.[citation needed]. Another researcher, Harriet Zuckerman, claims that when woman and man have similar abilities for a job, the probability of the woman getting the job is lower.[citation needed] Elizabeth Finkel agrees, saying, "In general, while woman and men seem to be completing doctorate with similar credentials and experience, the opposition and rewards they find are not comparable. Women tend to be treated with less salary and status, many policy makers notice this phenomenon and try to rectify the unfair situation for women participating in scientific fields."[174]
Societal disadvantages
Despite women's tendency to perform better than men academically, there are flaws involving stereotyping, lack of information, and family influence that have been found to affect women's involvement in science. Stereotyping has an effect, because people associate characteristics such as nurturing, kind, and warm or characteristics like strong and powerful with a particular gender. These character associations lead people to stereotype that certain jobs are more suitable to a particular gender.[175] Lack of information is something that many institutions have worked hard over the years to improve by making programs such as the IFAC project[176] (Information for a choice: empowering women through learning for scientific and technological career paths) which investigated low women participation in science and technology fields at high school to university level. However, not all efforts were as successful, "Science: it's a girl thing" campaign, which has since been removed, received backlash for further encouraging women that they must partake in "girly" or "feminine" activities.[176] The idea being that if women are fully informed of their career choices and employability, they will be more inclined to pursue STEM field jobs. Women also struggle in the sense of lacking role models of women in science.[176] Family influence is dependent on education level, economic status, and belief system.[177] Education level of a student's parent matters, because oftentimes people who have higher education have a different opinion on education's importance than someone that does not. A parent can also be an influence in the sense that they want their children to follow in their footsteps and pursue a similar occupation, especially in women, it's been found that the mother's line of work tends to correlate with their daughters.[178] Economic status can influence what kind of higher education a student might get. Economic status may influence their education depending on whether they are a work bound student or a college bound student. A work bound student may choose a shorter career path to quickly begin making money or due to lack of time. The belief system of a household can also have a big impact on women depending on their family's religious or cultural viewpoints. There are still some countries that have certain regulations on women's occupation, clothing, and curfew that limit career choices for women. Parental influence is also relevant because people tend to want to fulfill what they could not have as a child.[177] Unfortunately, women are at such a disadvantage because not only must they overcome societal norms but then they also have to outperform men for the same recognition, studies show.[179]
That sexism is alive and well in science is known. ...
Even in the life sciences, where men and women start careers in fairly equal numbers, the number of women drops off rapidly at professorial level.
On average, fewer than one in five science professors are female. Science punishes career breaks, and women who take time off to have children are immediately disadvantaged. "The flashpoint is when you’re about 35 and trying to get tenure. That can be when you’re trying to have kids, and it can play a major role in why you see so much attrition at that stage," said Jennifer Rohn, a cell biologist at University College London. A grant may give a woman a year’s grace if she has a baby, but it takes longer to get back into research projects than that.[180]
Contemporary advocacy and developments
Efforts to increase participation
A number of organizations have been set up to combat the stereotyping that may encourage girls away from careers in these areas. In the UK The WISE Campaign (Women into Science, Engineering and Construction) and the UKRC (The UK Resource Centre for Women in SET) are collaborating to ensure industry, academia and education are all aware of the importance of challenging the traditional approaches to careers advice and recruitment that mean some of the best brains in the country are lost to science. The UKRC and other women's networks provide female role models, resources and support for activities that promote science to girls and women. The Women's Engineering Society, a professional association in the UK, has been supporting women in engineering and science since 1919. In computing, the British Computer Society group BCSWomen is active in encouraging girls to consider computing careers, and in supporting women in the computing workforce.
In the United States, the Association for Women in Science is one of the most prominent organization for professional women in science. In 2011, the Scientista Foundation was created to empower pre-professional college and graduate women in science, technology, engineering and mathematics (STEM), to stay in the career track. There are also several organizations focused on increasing mentorship from a younger age. One of the best known groups is Science Club for Girls,[citation needed] which pairs undergraduate mentors with high school and middle school mentees. The model of that pairs undergraduate college mentors with younger students is quite popular. In addition, many young women are creating programs to boost participation in STEM at a younger level, either through conferences or competitions.
In efforts to make women scientists more visible to the general public, the Grolier Club in New York hosted a "landmark exhibition" titled "Extraordinary Women in Science & Medicine: Four Centuries of Achievement", showcasing the lives and works of 32 women scientists in 2003.[181] The National Institute for Occupational Safety and Health (NIOSH) developed a video series highlighting the stories of female researchers at NIOSH.[182] Each of the women featured in the videos share their journey into science, technology, engineering, or math (STEM), and offers encouragement to aspiring scientists.[182] NIOSH also partners with external organizations in efforts to introduce individuals to scientific disciplines and funds several science-based training programs across the country.[183][184]
Creative Resilience: Art by Women in Science is a multi–media exhibition and accompanying publication, produced in 2021 by the Gender Section of the United Nations Educational, Scientific and Cultural Organization (UNESCO). The project aims to give visibility to women, both professionals and university students, working in science, technology, engineering and mathematics (STEM). With short biographical information and graphic reproductions of their artworks dealing with the Covid-19 pandemic and accessible online, the project provides a platform for women scientists to express their experiences, insights, and creative responses to the pandemic.[185]
Kizzmekia Corbett, recognized as one of the leading scientists in the United States for vaccine research, is a true pioneer who is dedicated to promoting diversity and equity within her field. She is a part of a team at the National Institutes of Health that developed the one of the COVID-19 vaccines that is greater than 90% effective. Given the disproportionate impact of COVID-19 on African Americans and the long history of African American and female scientists being underrecognized, it is particularly significant to acknowledge the groundbreaking contributions of Dr. Corbett. [186]
In 2012, a journal article published in Proceedings of the National Academy of Sciences (PNAS) reported a gender bias among science faculty.[194] Faculty were asked to review a resume from a hypothetical student and report how likely they would be to hire or mentor that student, as well as what they would offer as starting salary. Two resumes were distributed randomly to the faculty, only differing in the names at the top of the resume (John or Jennifer). The male student was rated as significantly more competent, more likely to be hired, and more likely to be mentored. The median starting salary offered to the male student was greater than $3,000 over the starting salary offered to the female student. Both male and female faculty exhibited this gender bias. This study suggests bias may partly explain the persistent deficit in the number of women at the highest levels of scientific fields. Another study reported that men are favored in some domains, such as biology tenure rates, but that the majority of domains were gender-fair; the authors interpreted this to suggest that the under-representation of women in the professorial ranks was not solely caused by sexist hiring, promotion, and remuneration.[195] In April 2015 Williams and Ceci published a set of five national experiments showing that hypothetical female applicants were favored by faculty for assistant professorships over identically qualified men by a ratio of 2 to 1.[196]
Problematic public statements
In January 2005, Harvard University President Lawrence Summers sparked controversy at a National Bureau of Economic Research (NBER) Conference on Diversifying the Science & Engineering Workforce. Dr. Summers offered his explanation for the shortage of women in senior posts in science and engineering. He made comments suggesting the lower numbers of women in high-level science positions may in part be due to innate differences in abilities or preferences between men and women. Making references to the field and behavioral genetics, he noted the generally greater variability among men (compared to women) on tests of cognitive abilities,[202][203][204] leading to proportionally more men than women at both the lower and upper tails of the test score distributions. In his discussion of this, Summers said that "even small differences in the standard deviation [between genders] will translate into very large differences in the available pool substantially out [from the mean]".[205] Summers concluded his discussion by saying:[205]
So my best guess, to provoke you, of what's behind all of this is that the largest phenomenon, by far, is the general clash between people's legitimate family desires and employers' current desire for high power and high intensity, that in the special case of science and engineering, there are issues of intrinsic aptitude, and particularly of the variability of aptitude, and that those considerations are reinforced by what are in fact lesser factors involving socialization and continuing discrimination.
Despite his protégée, Sheryl Sandberg, defending Summers' actions and Summers offering his own apology repeatedly, the Harvard Graduate School of Arts and Sciences passed a motion of "lack of confidence" in the leadership of Summers who had allowed tenure offers to women plummet after taking office in 2001.[205] The year before he became president, Harvard extended 13 of its 36 tenure offers to women and by 2004 those numbers had dropped to 4 of 32 with several departments lacking even a single tenured female professor.[206] This controversy is speculated to have significantly contributed to Summers resignation from his position at Harvard the following year
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From Wikipedia, the free encyclopedia
This article is about the human condition. For other uses, see Health (disambiguation).
World Health Organization's definition
Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.
Source:
"Constitution". World Health Organization. Retrieved 10 December 2023.
Health has a variety of definitions, which have been used for different purposes over time. Health can be promoted by encouraging healthful activities, such as regular physical exercise and adequate sleep,[1] and by reducing or avoiding unhealthful activities or situations, such as smoking or excessive stress. Some factors affecting health are due to individual choices, such as whether to engage in a high-risk behavior, while others are due to structural causes, such as whether the society is arranged in a way that makes it easier or harder for people to get necessary healthcare services. Still, other factors are beyond both individual and group choices, such as genetic disorders.
History
The meaning of health has evolved over time. In keeping with the biomedical perspective, early definitions of health focused on the theme of the body's ability to function; health was seen as a state of normal function that could be disrupted from time to time by disease. An example of such a definition of health is: "a state characterized by anatomic, physiologic, and psychological integrity; ability to perform personally valued family, work, and community roles; ability to deal with physical, biological, psychological, and social stress".[2] Then, in 1948, in a radical departure from previous definitions, the World Health Organization (WHO) proposed a definition that aimed higher, linking health to well-being, in terms of "physical, mental, and social well-being, and not merely the absence of disease and infirmity".[3] Although this definition was welcomed by some as being innovative, it was also criticized for being vague and excessively broad and was not construed as measurable. For a long time, it was set aside as an impractical ideal, with most discussions of health returning to the practicality of the biomedical model.[4]
Just as there was a shift from viewing disease as a state to thinking of it as a process, the same shift happened in definitions of health. Again, the WHO played a leading role when it fostered the development of the health promotion movement in the 1980s. This brought in a new conception of health, not as a state, but in dynamic terms of resiliency, in other words, as "a resource for living". In 1984, WHO revised the definition of health defined it as "the extent to which an individual or group is able to realize aspirations and satisfy needs and to change or cope with the environment. Health is a resource for everyday life, not the objective of living; it is a positive concept, emphasizing social and personal resources, as well as physical capacities."[5] Thus, health referred to the ability to maintain homeostasis and recover from adverse events. Mental, intellectual, emotional and social health referred to a person's ability to handle stress, to acquire skills, to maintain relationships, all of which form resources for resiliency and independent living.[4] This opens up many possibilities for health to be taught, strengthened and learned.
Since the late 1970s, the federal Healthy People Program has been a visible component of the United States' approach to improving population health.[6] In each decade, a new version of Healthy People is issued,[7] featuring updated goals and identifying topic areas and quantifiable objectives for health improvement during the succeeding ten years, with assessment at that point of progress or lack thereof. Progress has been limited to many objectives, leading to concerns about the effectiveness of Healthy People in shaping outcomes in the context of a decentralized and uncoordinated US health system. Healthy People 2020 gives more prominence to health promotion and preventive approaches and adds a substantive focus on the importance of addressing social determinants of health. A new expanded digital interface facilitates use and dissemination rather than bulky printed books as produced in the past. The impact of these changes to Healthy People will be determined in the coming years.[8]
Systematic activities to prevent or cure health problems and promote good health in humans are undertaken by health care providers. Applications with regard to animal health are covered by the veterinary sciences. The term "healthy" is also widely used in the context of many types of non-living organizations and their impacts for the benefit of humans, such as in the sense of healthy communities, healthy cities or healthy environments. In addition to health care interventions and a person's surroundings, a number of other factors are known to influence the health status of individuals. These are referred to as the "determinants of health", which include the individual's background, lifestyle, economic status, social conditions and spirituality; Studies have shown that high levels of stress can affect human health.[9]
In the first decade of the 21st century, the conceptualization of health as an ability opened the door for self-assessments to become the main indicators to judge the performance of efforts aimed at improving human health.[10] It also created the opportunity for every person to feel healthy, even in the presence of multiple chronic diseases or a terminal condition, and for the re-examination of determinants of health (away from the traditional approach that focuses on the reduction of the prevalence of diseases).[11]
Determinants
See also: Social determinants of health and Risk factor
In general, the context in which an individual lives is of great importance for both his health status and quality of life. It is increasingly recognized that health is maintained and improved not only through the advancement and application of health science, but also through the efforts and intelligent lifestyle choices of the individual and society. According to the World Health Organization, the main determinants of health include the social and economic environment, the physical environment, and the person's individual characteristics and behaviors.[12]
More specifically, key factors that have been found to influence whether people are healthy or unhealthy include the following:[12][13][14]
Education and literacy
Employment/working conditions
Income and social status
Physical environments
Social environments
Social support networks
Biology and genetics
Culture
Gender
Health care services
Healthy child development
Personal health practices and coping skills
Donald Henderson as part of the CDC's smallpox eradication team in 1966
An increasing number of studies and reports from different organizations and contexts examine the linkages between health and different factors, including lifestyles, environments, health care organization and health policy, one specific health policy brought into many countries in recent years was the introduction of the sugar tax. Beverage taxes came into light with increasing concerns about obesity, particularly among youth. Sugar-sweetened beverages have become a target of anti-obesity initiatives with increasing evidence of their link to obesity.[15]—such as the 1974 Lalonde report from Canada;[14] the Alameda County Study in California;[16] and the series of World Health Reports of the World Health Organization, which focuses on global health issues including access to health care and improving public health outcomes, especially in developing countries.[17]
The concept of the "health field," as distinct from medical care, emerged from the Lalonde report from Canada. The report identified three interdependent fields as key determinants of an individual's health. These are:[14]
Biomedical: all aspects of health, physical and mental, developed within the human body as influenced by genetic make-up.
Environmental: all matters related to health external to the human body and over which the individual has little or no control;
Lifestyle: the aggregation of personal decisions (i.e., over which the individual has control) that can be said to contribute to, or cause, illness or death;
The maintenance and promotion of health is achieved through different combination of physical, mental, and social well-being—a combination sometimes referred to as the "health triangle."[18] The WHO's 1986 Ottawa Charter for Health Promotion further stated that health is not just a state, but also "a resource for everyday life, not the objective of living. Health is a positive concept emphasizing social and personal resources, as well as physical capacities."[19]
aggression, dissociation) that develop to adapt to problems with early objects (e.g., caregivers) and empathic failures in childhood. For example, persistent parental discouragement of anger may result in repression/suppression of angry feelings which manifests as gastrointestinal distress (somatization) when provoked by another while the anger remains unconscious and outside the individual's awareness. Such conflicts can be targets for successful treatment with psychodynamic therapy. While psychodynamic therapy tends to explore the underlying roots of anxiety, cognitive behavioral therapy has also been shown to be a successful treatment for anxiety by altering irrational thoughts and unwanted behaviors.
Evolutionary psychology
An evolutionary psychology explanation is that increased anxiety serves the purpose of increased vigilance regarding potential threats in the environment as well as increased tendency to take proactive actions regarding such possible threats. This may cause false positive reactions but an individual with anxiety may also avoid real threats. This may explain why anxious people are less likely to die due to accidents.[137] There is ample empirical evidence that anxiety can have adaptive value. Within a school, timid fish are more likely than bold fish to survive a predator.[138]
When people are confronted with unpleasant and potentially harmful stimuli such as foul odors or tastes, PET-scans show increased blood flow in the amygdala.[139][140] In these studies, the participants also reported moderate anxiety. This might indicate that anxiety is a protective mechanism designed to prevent the organism from engaging in potentially harmful behaviors.
Social
Social risk factors for anxiety include a history of trauma (e.g., physical, sexual or emotional abuse or assault), bullying, early life experiences and parenting factors (e.g., rejection, lack of warmth, high hostility, harsh discipline, high parental negative affect, anxious childrearing, modelling of dysfunctional and drug-abusing behaviour, discouragement of emotions, poor socialization, poor attachment, and child abuse and neglect), cultural factors (e.g., stoic families/cultures, persecuted minorities including those with disabilities), and socioeconomics (e.g., uneducated, unemployed, impoverished although developed countries have higher rates of anxiety disorders than developing countries).[141] A 2019 comprehensive systematic review of over 50 studies showed that food insecurity in the United States is strongly associated with depression, anxiety, and sleep disorders.[142] Food-insecure individuals had an almost 3 fold risk increase of testing positive for anxiety when compared to food-secure individuals.
Gender socialization
Contextual factors that are thought to contribute to anxiety include gender socialization and learning experiences. In particular, learning mastery (the degree to which people perceive their lives to be under their own control) and instrumentality, which includes such traits as self-confidence, self-efficacy, independence, and competitiveness fully mediate the relation between gender and anxiety. That is, though gender differences in anxiety exist, with higher levels of anxiety in women compared to men, gender socialization and learning mastery explain these gender differences.[143]
Treatment
See also: Fear § Management
The first step in the management of a person with anxiety symptoms involves evaluating the possible presence of an underlying medical cause, the recognition of which is essential in order to decide the correct treatment.[25][118] Anxiety symptoms may mask an organic disease, or appear associated with or as a result of a medical disorder.[25][118][144][26]
Cognitive behavioral therapy (CBT) is effective for anxiety disorders and is a first line treatment.[145][146][147][148][149] CBT appears to be equally effective when carried out via the internet.[149] While evidence for mental health apps is promising, it is preliminary.[150][151]
Anxiety often affects relationships, and interpersonal psychotherapy addresses these issues by improving communication and relationship skills.[152]
Psychopharmacological treatment can be used in parallel to CBT or can be used alone. As a general rule, most anxiety disorders respond well to first-line agents. Such drugs, also used as anti-depressants, are the selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors, that work by blocking the reuptake of specific neurotransmitters and resulting in the increase in availability of these neurotransmitters. Additionally, benzodiazepines are often prescribed to individuals with anxiety disorder. Benzodiazepines produce an anxiolytic response by modulating GABA and increasing its receptor binding. A third common treatment involves a category of drug known as serotonin agonists. This category of drug works by initiating a physiological response at 5-HT1A receptor by increasing the action of serotonin at this receptor.[citation needed] Other treatment options include pregabalin, tricyclic antidepressants, and moclobemide, among others.[153]
Anxiety is considered to be a serious psychiatric illness that has an unknown true pervasiveness due to affected individuals not asking for proper treatment or aid, and due to professionals missing the diagnosis.[3]
Prevention
The above risk factors give natural avenues for prevention. A 2017 review found that psychological or educational interventions have a small yet statistically significant benefit for the prevention of anxiety in varied population types.[154][155][156]
Pathophysiology
Anxiety disorder appears to be a genetically inherited neurochemical dysfunction that may involve autonomic imbalance; decreased GABA-ergic tone; allelic polymorphism of the catechol-O-methyltransferase (COMT) gene; increased adenosine receptor function; increased cortisol.[157]
In the central nervous system (CNS), the major mediators of the symptoms of anxiety disorders appear to be norepinephrine, serotonin, dopamine, and gamma-aminobutyric acid (GABA). Other neurotransmitters and peptides, such as corticotropin-releasing factor, may be involved. Peripherally, the autonomic nervous system, especially the sympathetic nervous system, mediates many of the symptoms. Increased flow in the right parahippocampal region and reduced serotonin type 1A receptor binding in the anterior and posterior cingulate and raphe of patients are the diagnostic factors for prevalence of anxiety disorder.
The amygdala is central to the processing of fear and anxiety,[158] and its function may be disrupted in anxiety disorders. Anxiety processing in the basolateral amygdala has been implicated with expansion of dendritic arborization of the amygdaloid neurons.[159] SK2 potassium channels mediate inhibitory influence on action potentials and reduce arborization.[160]
Vitamin B6 is one of the B vitamins, and thus an essential nutrient.[1][2][3][4] The term refers to a group of six chemically similar compounds, i.e., "vitamers", which can be interconverted in biological systems. Its active form, pyridoxal 5′-phosphate, serves as a coenzyme in more than 140 enzyme reactions in amino acid, glucose, and lipid metabolism.[1][2][3]
Plants synthesize pyridoxine as a means of protection from the UV-B radiation found in sunlight[5] and for the role it plays in the synthesis of chlorophyll.[6] Animals cannot synthesize any of the various forms of the vitamin, and hence must obtain it via diet, either of plants, or of other animals. There is some absorption of the vitamin produced by intestinal bacteria, but this is not sufficient to meet dietary needs. For adult humans, recommendations from various countries' food regulatory agencies are in the range of 1.0 to 2.0 milligrams (mg) per day. These same agencies also recognize ill effects from intakes that are too high, and so set safe upper limits, ranging from as low as 25 mg/day to as high as 100 mg/day depending on the country. Beef, pork, fowl and fish are generally good sources; dairy, eggs, mollusks and crustaceans also contain vitamin B6, but at lower levels. There is enough in a wide variety of plant foods so that a vegetarian or vegan diet does not put consumers at risk for deficiency.[7]
Dietary deficiency is rare. Classic clinical symptoms include rash and inflammation around the mouth and eyes, plus neurological effects that include drowsiness and peripheral neuropathy affecting sensory and motor nerves in the hands and feet. In addition to dietary shortfall, deficiency can be the result of anti-vitamin drugs. There are also rare genetic defects that can trigger vitamin B6 deficiency-dependent epileptic seizures in infants. These are responsive to pyridoxal 5'-phosphate therapy.[8]
Definition
Pyridoxine (PN)
Pyridoxamine (PM)
Pyridoxal (PL)
Vitamin B6 is a water-soluble vitamin, one of the B vitamins. The vitamin actually comprises a group of six chemically related compounds, i.e., vitamers, that all contain a pyridine ring as their core. These are pyridoxine, pyridoxal, pyridoxamine, and their respective phosphorylated derivatives pyridoxine 5'-phosphate, pyridoxal 5'-phosphate and pyridoxamine 5'-phosphate. Pyridoxal 5'-phosphate has the highest biological activity, but the others are convertible to that form.[9] Vitamin B6 serves as a co-factor in more than 140 cellular reactions, mostly related to amino acid biosynthesis and catabolism, but is also involved in fatty acid biosynthesis and other physiological functions.[1][2][3]
Forms
Because of its chemical stability, pyridoxine hydrochloride is the form most commonly given as vitamin B6 dietary supplement. Absorbed pyridoxine (PN) is converted to pyridoxamine 5'-phosphate (PMP) by the enzyme pyridoxal kinase, with PMP further converted to pyridoxal 5'-phosphate (PLP), the metabolically active form, by the enzymes pyridoxamine-phosphate transaminase or pyridoxine 5'-phosphate oxidase, the latter of which also catalyzes the conversion of pyridoxine 5′-phosphate (PNP) to PLP.[3][9] Pyridoxine 5'-phosphate oxidase is dependent on flavin mononucleotide (FMN) as a cofactor produced from riboflavin (vitamin B2). For degradation, in a non-reversible reaction, PLP is catabolized to 4-pyridoxic acid, which is excreted in urine.[3]
Synthesis
Biosynthesis
Main article: Pyridoxal phosphate § Biosynthesis
Two pathways for PLP are currently known: one requires deoxyxylulose 5-phosphate (DXP), while the other does not, hence they are known as DXP-dependent and DXP-independent. These pathways have been studied extensively in Escherichia coli[10] and Bacillus subtilis, respectively. Despite the disparity in the starting compounds and the different number of steps required, the two pathways possess many commonalities.[11] The DXP-dependent pathway:
Commercial synthesis
The starting material is either the amino acid alanine, or propionic acid converted into alanine via halogenation and amination. Then, the procedure accomplishes the conversion of the amino acid into pyridoxine through the formation of an oxazole intermediate followed by a Diels–Alder reaction, with the entire process referred to as the "oxazole method".[9][12] The product used in dietary supplements and food fortification is pyridoxine hydrochloride, the chemically stable hydrochloride salt of pyridoxine.[13] Pyridoxine is converted in the liver into the metabolically active coenzyme form pyridoxal 5'-phosphate. At present, while the industry mainly utilizes the oxazole method, there is research exploring means of using less toxic and dangerous reagents in the process.[14] Fermentative bacterial biosynthesis methods are also being explored, but are not yet scaled up for commercial production.[13]
Functions
PLP is involved in many aspects of macronutrient metabolism, neurotransmitter synthesis, histamine synthesis, hemoglobin synthesis and function, and gene expression. PLP generally serves as a coenzyme (cofactor) for many reactions including decarboxylation, transamination, racemization, elimination, replacement, and beta-group interconversion.[2][3][15]
Amino acid metabolism
Transaminases break down amino acids with PLP as a cofactor. The proper activity of these enzymes is crucial for the process of moving amine groups from one amino acid to another. To function as a transaminase coenzyme, PLP bound to a lysine of the enzyme then binds to a free amino acid via formation of a Schiff's base. The process then dissociates the amine group from the amino acid, releasing a keto acid, then transfers the amine group to a different keto acid to create a new amino acid.[3]
Serine racemase which synthesizes the neuromodulator D-serine from its enantiomer is a PLP-dependent enzyme.
PLP is a coenzyme needed for the proper function of the enzymes cystathionine synthase and cystathionase. These enzymes catalyze reactions in the catabolism of methionine. Part of this pathway (the reaction catalyzed by cystathionase) also produces cysteine.
Selenomethionine is the primary dietary form of selenium. PLP is needed as a cofactor for the enzymes that allow selenium to be used from the dietary form. PLP also plays a cofactor role in releasing selenium from selenohomocysteine to produce hydrogen selenide, which can then be used to incorporate selenium into selenoproteins.
PLP is required for the conversion of tryptophan to niacin, so low vitamin B6 status impairs this conversion.[15]
Neurotransmitters
PLP is a cofactor in the biosynthesis of five important neurotransmitters: serotonin, dopamine, epinephrine, norepinephrine, and gamma-aminobutyric acid.[6]
Glucose metabolism
PLP is a required coenzyme of glycogen phosphorylase, the enzyme necessary for glycogenolysis. Glycogen serves as a carbohydrate storage molecule, primarily found in muscle, liver and brain. Its breakdown frees up glucose for energy.[6] PLP also catalyzes transamination reactions that are essential for providing amino acids as a substrate for gluconeogenesis, the biosynthesis of glucose.[15]
Lipid metabolism
PLP is an essential component of enzymes that facilitate the biosynthesis of sphingolipids.[15] Particularly, the synthesis of ceramide requires PLP. In this reaction, serine is decarboxylated and combined with palmitoyl-CoA to form sphinganine, which is combined with a fatty acyl-CoA to form dihydroceramide. This compound is then further desaturated to form ceramide. In addition, the breakdown of sphingolipids is also dependent on vitamin B6 because sphingosine-1-phosphate lyase, the enzyme responsible for breaking down sphingosine-1-phosphate, is also PLP-dependent.
Hemoglobin synthesis and function
PLP aids in the synthesis of hemoglobin, by serving as a coenzyme for the enzyme aminolevulinic acid synthase.[6] It also binds to two sites on hemoglobin to enhance the oxygen binding of hemoglobin.[15]
Gene expression
PLP has been implicated in increasing or decreasing the expression of certain genes. Increased intracellular levels of the vitamin lead to a decrease in the transcription of glucocorticoids. Vitamin B6 deficiency leads to the increased gene expression of albumin mRNA. Also, PLP influences expression of glycoprotein IIb by interacting with various transcription factors; the result is inhibition of platelet aggregation.[15]
In plants
Plant synthesis of vitamin B6 contributes to protection from sunlight. Ultraviolet-B radiation (UV-B) from sunlight stimulates plant growth, but in high amounts can increase production of tissue-damaging reactive oxygen species (ROS), i.e., oxidants. Using Arabidopsis thaliana (common name: thale cress), researchers demonstrated that UV-B exposure increased pyridoxine biosynthesis, but in a mutant variety, pyridoxine biosynthesis capacity was not inducible, and as a consequence, ROS levels, lipid peroxidation, and cell proteins associated with tissue damage were all elevated.[5][16][17] Biosynthesis of chlorophyll depends on aminolevulinic acid synthase, a PLP-dependent enzyme that uses succinyl-CoA and glycine to generate aminolevulinic acid, a chlorophyll precursor.[6] In addition, plant mutants with severely limited capacity to synthesize vitamin B6 have stunted root growth, because synthesis of plant hormones such as auxin require the vitamin as an enzyme cofactor.[6]
Medical uses
Further information: Pyridoxine
Isoniazid is an antibiotic used for the treatment of tuberculosis. Common side effect include numbness in the hands and feet, also known as peripheral neuropathy.[18] Co-treatment with vitamin B6 alleviates the numbness.[19]
Overconsumption of seeds from Ginkgo biloba can deplete vitamin B6, because the ginkgotoxin is an anti-vitamin (vitamin antagonist). Symptoms include vomiting and generalized convulsions. Ginkgo seed poisoning can be treated with vitamin B6.[20][21]
Dietary recommendations
This section is missing information about definition of "milligram of B6" given the many vitamers. Please expand the section to include this information. Further details may exist on the talk page. (September 2022)
The US National Academy of Medicine updated Dietary Reference Intakes for many vitamins in 1998. Recommended Dietary Allowances (RDAs), expressed as milligrams per day, increase with age from 1.2 to 1.5 mg/day for women and from 1.3 to 1.7 mg/day for men. The RDA for pregnancy is 1.9 mg/day, for lactation, 2.0 mg/day. For children ages 1–13 years the RDA increases with age from 0.5 to 1.0 mg/day. As for safety, Tolerable upper intake levels (ULs) for vitamins and minerals are identified when evidence is sufficient. In the case of vitamin B6 the adult UL is set at 100 mg/day.[4]
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA. For women and men ages 15 and older the PRI is set at 1.6 and 1.7 mg/day, respectively; for pregnancy 1.8 mg/day, for lactation 1.7 mg/day. For children ages 1–14 years the PRIs increase with age from 0.6 to 1.4 mg/day.[22] The EFSA also reviewed the safety question and set its UL at 25 mg/day.[23][24]
The Japanese Ministry of Health, Labour and Welfare updated its vitamin and mineral recommendations in 2015. The adult RDAs are at 1.2 mg/day for women 1.4 mg/day for men. The RDA for pregnancy is 1.4 mg/day, for lactation is 1.5 mg/day. For children ages 1–17 years the RDA increases with age from 0.5 to 1.5 mg/day. The adult UL was set at 40–45 mg/day for women and 50–60 mg/day for men, with the lower values in those ranges for adults over 70 years of age.[25]
Safety
Main article: Megavitamin-B6 syndrome
Adverse effects have been documented from vitamin B6 dietary supplements, but never from food sources. Even though it is a water-soluble vitamin and is excreted in the urine, doses of pyridoxine in excess of the dietary upper limit (UL) over long periods cause painful and ultimately irreversible neurological problems.[4] The primary symptoms are pain and numbness of the extremities. In severe cases, motor neuropathy may occur with "slowing of motor conduction velocities, prolonged F wave latencies, and prolonged sensory latencies in both lower extremities", causing difficulty in walking. Sensory neuropathy typically develops at doses of pyridoxine in excess of 1,000 mg per day, but adverse effects can occur with much less, so intakes over 200 mg/day are not considered safe.[4] Trials with amounts equal to or less than 200 mg/day established that as a "No-observed-adverse-effect level", meaning the highest amount at which no adverse effects were observed. This was divided by two to allow for people who might be extra sensitive to the vitamin, referred to as an "uncertainty factor", resulting in the aforementioned adult UL of 100 mg/day.[4]
Labeling
For US food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value. For vitamin B6 labeling purposes 100% of the Daily Value was 2.0 mg, but as of May 27, 2016, it was revised to 1.7 mg to bring it into agreement with the adult RDA.[26][27] A table of the old and new adult daily values is provided at Reference Daily Intake.
Sources
Bacteria residing in the large intestine are known to synthesize B-vitamins, including B6, but the amounts are not sufficient to meet host requirements, in part because the vitamins are competitively taken up by non-synthesizing bacteria.[28]
Vitamin B6 is found in a wide variety of foods. In general, meat, fish and fowl are good sources, but dairy foods and eggs are not (table).[29][30] Crustaceans and mollusks contain about 0.1 mg/100 grams. Fruit (apples, oranges, pears) contain less than 0.1 mg/100g.[30]
Bioavailability from a mixed diet (containing animal- and plant-sourced foods) is estimated at being 75% – higher for PLP from meat, fish and fowl, lower from plants, as those are mostly in the form of pyridoxine glucoside, which has approximately half the bioavailability of animal-sourced B6 because removal of the glucoside by intestinal cells is not 100% efficient.[4] Given lower amounts and lower bioavailability of the vitamin from plants there was a concern that a vegetarian or vegan diet could cause a vitamin deficiency state. However, the results from a population-based survey conducted in the U.S. demonstrated that despite a lower vitamin intake, serum PLP was not significantly different between meat-eaters and vegetarians, suggesting that a vegetarian diet does not pose a risk for vitamin B6 deficiency.[7]
Cooking, storage, and processing losses vary, and in some foods may be more than 50% depending on the form of vitamin present in the food.[3] Plant foods lose less during processing, as they contain pyridoxine, which is more stable than the pyridoxal or pyridoxamine forms found in animal-sourced foods. For example, milk can lose 30–70% of its vitamin B6 content when dried.[15] The vitamin is found in the germ and aleurone layer of grains, so there is more in whole wheat bread compared to white bread wheat, and more in brown rice compared to white rice.[30]
Most values shown in the table are rounded to nearest tenth of a milligram:
Source[29][30] Amount
(mg per 100 grams)
Whey protein concentrate 1.2
Beef liver, pan-fried 1.0
Tuna, skipjack, cooked 1.0
Beef steak, grilled 0.9
Salmon, Atlantic, cooked 0.9
Chicken breast, grilled 0.7
Pork chop, cooked 0.6
Turkey, ground, cooked 0.6
Banana 0.4
Source[29][30] Amount
(mg per 100 grams)
Mushroom, Shiitake, raw 0.3
Potato, baked, with skin 0.3
Sweet potato baked 0.3
Bell pepper, red 0.3
Peanuts 0.3
Avocado 0.25
Spinach 0.2
Chickpeas 0.1
Tofu, firm 0.1
Source[30] Amount
(mg per 100 grams)
Corn grits 0.1
Milk, whole 0.1 (one cup)
Yogurt 0.1 (one cup)
Almonds 0.1
Bread, whole wheat/white 0.2/0.1
Rice, cooked, brown/white 0.15/0.02
Beans, baked 0.1
Beans, green 0.1
Chicken egg 0.1
Fortification
As of 2019, fourteen countries require food fortification of wheat flour, maize flour or rice with vitamin B6 as pyridoxine hydrochloride. Most of these are in southeast Africa or Central America. The amounts stipulated range from 3.0 to 6.5 mg/kg. An additional seven countries, including India, have a voluntary fortification program. India stipulates 2.0 mg/kg.[31]
Dietary supplements
In the US, multi-vitamin/mineral products typically contain 2 to 4 mg of vitamin B6 per daily serving as pyridoxine hydrochloride, but a few contain more than 25 mg. Many US dietary supplement companies also market a B6-only dietary supplement with 100 mg per daily serving.[1] While the US National Academy of Medicine sets an adult safety UL at 100 mg/day,[1][4] the European Food Safety Authority sets its UL at 25 mg/day.[23][24]
Health claims
The Japanese Ministry of Health, Labor, and Welfare (MHLW) set up the 'Foods for Specified Health Uses' (特定保健用食品; FOSHU) regulatory system in 1991 to individually approve the statements made on food labels concerning the effects of foods on the human body. The regulatory range of FOSHU was later broadened to allow for the certification of capsules and tablets. In 2001, MHLW enacted a new regulatory system, 'Foods with Health Claims' (保健機能食品; FHC), which consists of the existing FOSHU system and the newly established 'Foods with Nutrient Function Claims' (栄養機能表示食品; FNFC), under which claims were approved for any product containing a specified amount per serving of 12 vitamins, including vitamin B6, and two minerals.[32][33] To make a health claim based on a food's vitamin B6 content, the amount per serving must be in the range of 0.3–25 mg. The allowed claim is: "Vitamin B6 is a nutrient that helps produce energy from protein and helps maintain healthy skin and mucous membranes."[34][35]
In 2010, the European Food Safety Authority (EFSA) published a review of proposed health claims for vitamin B6, disallowing claims for bone, teeth, hair skin and nails, and allowing claims that the vitamin provided for normal homocysteine metabolism, normal energy-yielding metabolism, normal psychological function, reduced tiredness and fatigue, and provided for normal cysteine synthesis.[36]
The US Food and Drug Administration (FDA) has several processes for permitting health claims on food and dietary supplement labels.[37] There are no FDA-approved Health Claims or Qualified Health Claims for vitamin B6. Structure/Function Claims can be made without FDA review or approval as long as there is some credible supporting science.[37] Examples for this vitamin are "Helps support nervous system function" and "Supports healthy homocysteine metabolism."
Absorption, metabolism and excretion
Vitamin B6 is absorbed in the jejunum of the small intestine by passive diffusion.[1][4] Even extremely large amounts are well absorbed. Absorption of the phosphate forms involves their dephosphorylation catalyzed by the enzyme alkaline phosphatase.[15] Most of the vitamin is taken up by the liver. There, the dephosphorylated vitamins are converted to the phosphorylated PLP, PNP and PMP, with the two latter converted to PLP. In the liver, PLP is bound to proteins, primarily albumin. The PLP-albumin complex is what is released by the liver to circulate in plasma.[4] Protein-binding capacity is the limiting factor for vitamin storage. Total body stores, the majority in muscle, with a lesser amount in liver, have been estimated to be in the range of 61 to 167 mg.[4]
Enzymatic processes utilize PLP as a phosphate-donating cofactor. PLP is restored via a salvage pathway that requires three key enzymes, pyridoxal kinase, pyridoxine 5'-phosphate oxidase, and phosphatases.[6][8] Inborn errors in the salvage enzymes are known to cause inadequate levels of PLP in the cell, particularly in neuronal cells. The resulting PLP deficiency is known to cause or implicated in several pathologies, most notably infant epileptic seizures.[8]
The half-life of vitamin B6 varies according to different sources: one source suggests that the half-life of pyridoxine is up to 20 days,[38] while another source indicates half-life of vitamin B6 is in range of 25 to 33 days.[39] After considering the different sources, it can be concluded that the half-life of vitamin B6 is typically measured in several weeks.[38][39]
The end-product of vitamin B6 catabolism is 4-pyridoxic acid, which makes up about half of the B6 compounds in urine. 4-Pyridoxic acid is formed by the action of aldehyde oxidase in the liver. Amounts excreted increase within 1–2 weeks with vitamin supplementation and decrease as rapidly after supplementation ceases.[4][40] Other vitamin forms excreted in the urine include pyridoxal, pyridoxamine and pyridoxine, and their phosphates. When large doses of pyridoxine are given orally, the proportion of these other forms increases. A small amount of vitamin B6 is also excreted in the feces. This may be a combination of unabsorbed vitamin and what was synthesized by large intestine microbiota.[4]
Deficiency
Signs and symptoms
The classic clinical syndrome for vitamin B6 deficiency is a seborrheic dermatitis-like eruption, atrophic glossitis with ulceration, angular cheilitis, conjunctivitis, intertrigo, abnormal electroencephalograms, microcytic anemia (due to impaired heme synthesis), and neurological symptoms of somnolence, confusion, depression, and neuropathy (due to impaired sphingosine synthesis).[1]
In infants, a deficiency in vitamin B6 can lead to irritability, abnormally acute hearing, and convulsive seizures.[1]
Less severe cases present with metabolic disease associated with insufficient activity of the coenzyme pyridoxal 5' phosphate (PLP).[1] The most prominent of the lesions is due to impaired tryptophan–niacin conversion. This can be detected based on urinary excretion of xanthurenic acid after an oral tryptophan load. Vitamin B6 deficiency can also result in impaired transsulfuration of methionine to cysteine. The PLP-dependent transaminases and glycogen phosphorylase provide the vitamin with its role in gluconeogenesis, so deprivation of vitamin B6 results in impaired glucose tolerance.[1][15]
Diagnosis
The assessment of vitamin B6 status is essential, as the clinical signs and symptoms in less severe cases are not specific.[41] The three biochemical tests most widely used are plasma PLP concentrations, the activation coefficient for the erythrocyte enzyme aspartate aminotransferase, and the urinary excretion of vitamin B6 degradation products, specifically urinary PA. Of these, plasma PLP is probably the best single measure, because it reflects tissue stores. Plasma PLP of less than 10 nmol/L is indicative of vitamin B6 deficiency.[40] A PLP concentration greater than 20 nmol/L has been chosen as a level of adequacy for establishing Estimated Average Requirements and Recommended Daily Allowances in the USA.[4] Urinary PA is also an indicator of vitamin B6 deficiency; levels of less than 3.0 mmol/day is suggestive of vitamin B6 deficiency.[40] Other methods of measurement, including UV spectrometric, spectrofluorimetric, mass spectrometric, thin-layer and high-performance liquid chromatographic, electrophoretic, electrochemical, and enzymatic, have been developed.[40][42]
The classic clinical symptoms for vitamin B6 deficiency are rare, even in developing countries. A handful of cases were seen between 1952 and 1953, particularly in the United States, having occurred in a small percentage of infants who were fed a formula lacking in pyridoxine.[43]
Causes
A deficiency of vitamin B6 alone is relatively uncommon and often occurs in association with other vitamins of the B complex. Evidence exists for decreased levels of vitamin B6 in women with type 1 diabetes and in patients with systemic inflammation, liver disease, rheumatoid arthritis, and those infected with HIV.[44][45] Use of oral contraceptives and treatment with certain anticonvulsants, isoniazid, cycloserine, penicillamine, and hydrocortisone negatively impact vitamin B6 status.[1][46][47] Hemodialysis reduces vitamin B6 plasma levels.[48]
Genetic defects
Genetically confirmed diagnoses of diseases affecting vitamin B6 metabolism (ALDH7A1 deficiency, pyridoxine-5'-phosphate oxidase deficiency, PLP binding protein deficiency, hyperprolinaemia type II and hypophosphatasia) can trigger vitamin B6 deficiency-dependent epileptic seizures in infants. These are responsive to pyridoxal 5'-phosphate therapy.[8][49]
History
Further information: Vitamin § History
An overview of the history was published in 2012.[50] In 1934, the Hungarian physician Paul György discovered a substance that was able to cure a skin disease in rats (dermatitis acrodynia). He named this substance vitamin B6, as numbering of the B vitamins was chronological, and pantothenic acid had been assigned vitamin B5 in 1931.[51][52] In 1938, Richard Kuhn was awarded the Nobel Prize in Chemistry for his work on carotenoids and vitamins, specifically B2 and B6.[53] Also in 1938, Samuel Lepkovsky isolated vitamin B6 from rice bran.[50] A year later, Stanton A. Harris and Karl August Folkers determined the structure of pyridoxine and reported success in chemical synthesis,[54] and then in 1942 Esmond Emerson Snell developed a microbiological growth assay that led to the characterization of pyridoxamine, the aminated product of pyridoxine, and pyridoxal, the formyl derivative of pyridoxine.[50] Further studies showed that pyridoxal, pyridoxamine, and pyridoxine have largely equal activity in animals and owe their vitamin activity to the ability of the organism to convert them into the enzymatically active form pyridoxal-5-phosphate.[50]
Following a recommendation of IUPAC-IUB in 1973,[55] vitamin B6 is the official name for all 2-methyl,3-hydroxy,5-hydroxymethylpyridine derivatives exhibiting the biological activity of pyridoxine.[56] Because these related compounds have the same effect, the word "pyridoxine" should not be used as a synonym for vitamin B6.
Research
Observational studies suggested an inverse correlation between a higher intake of vitamin B6 and all cancers, with the strongest evidence for gastrointestinal cancers. However, evidence from a review of randomized clinical trials did not support a protective effect. The authors noted that high B6 intake may be an indicator of higher consumption of other dietary protective micronutrients.[57] A review and two observational trials reporting lung cancer risk reported that serum vitamin B6 was lower in people with lung cancer compared to people without lung cancer, but did not incorporate any intervention or prevention trials.[58][59][60]
According to a prospective cohort study the long-term use of vitamin B6 from individual supplement sources at greater than 20 mg per day, which is more than ten times the adult male RDA of 1.7 mg/day, was associated with an increased risk for lung cancer among men. Smoking further elevated this risk.[61] However, a more recent review of this study suggested that a causal relationship between supplemental vitamin B6 and an increased lung cancer risk cannot be confirmed yet.[62]
For coronary heart disease, a meta-analysis reported lower relative risk for a 0.5 mg/day increment in dietary vitamin B6 intake.[63] As of 2021, there were no published reviews of randomized clinical trials for coronary heart disease or cardiovascular disease. In reviews of observational and intervention trials, neither higher vitamin B6 concentrations[64] nor treatment[65] showed any significant benefit on cognition and dementia risk. Low dietary vitamin B6 correlated with a higher risk of depression in women but not in men.[66] When treatment trials were reviewed, no meaningful treatment effect for depression was reported, but a subset of trials in pre-menopausal women suggested a benefit, with a recommendation that more research was needed.[67] The results of several trials with children diagnosed as having autism spectrum disorder (ASD) treated with high dose vitamin B6 and magnesium did not result in treatment effect on the severity of symptoms of ASD.[68]
A dietary supplement is a manufactured product intended to supplement a person's diet by taking a pill, capsule, tablet, powder, or liquid.[2] A supplement can provide nutrients either extracted from food sources, or that are synthetic (in order to increase the quantity of their consumption). The classes of nutrient compounds in supplements include vitamins, minerals, fiber, fatty acids, and amino acids. Dietary supplements can also contain substances that have not been confirmed as being essential to life, and so are not nutrients per se, but are marketed as having a beneficial biological effect, such as plant pigments or polyphenols. Animals can also be a source of supplement ingredients, such as collagen from chickens or fish for example. These are also sold individually and in combination, and may be combined with nutrient ingredients. The European Commission has also established harmonized rules to help insure that food supplements are safe and appropriately labeled.[3]
Creating an industry estimated to have a value of $151.9 billion in 2021,[4] there are more than 50,000 dietary supplement products marketed in the United States,[5] where about 50% of the American adult population consumes dietary supplements. Multivitamins are the most commonly used product among types of dietary supplements.[6] The United States National Institutes of Health states that supplements "may be of value" for those who are nutrient deficient from their diet and receive approval from their medical provider.[7]
In the United States, it is against federal regulations for supplement manufacturers to claim that these products prevent or treat any disease. Companies are allowed to use what is referred to as "Structure/Function" wording if there is substantiation of scientific evidence for a supplement providing a potential health effect.[8] An example would be "_____ helps maintain healthy joints", but the label must bear a disclaimer that the Food and Drug Administration (FDA) "has not evaluated the claim" and that the dietary supplement product is not intended to "diagnose, treat, cure or prevent any disease", because only a drug can legally make such a claim.[8] The FDA enforces these regulations and also prohibits the sale of supplements and supplement ingredients that are dangerous, or supplements not made according to standardized good manufacturing practices (GMPs).
Definition
In the United States, the Dietary Supplement Health and Education Act of 1994 provides this description: "The Dietary Supplement Health and Education Act of 1994 (DSHEA) defines the term "dietary supplement" to mean a product (other than tobacco) intended to supplement the diet that bears or contains one or more of the following dietary ingredients: a vitamin, a mineral, an herb or other botanical, an amino acid, a dietary substance for use by man to supplement the diet by increasing the total dietary intake, or a concentrate, metabolite, constituent, extract, or combination of any of the aforementioned ingredients. Furthermore, a dietary supplement must be labeled as a dietary supplement and be intended for ingestion and must not be represented for use as conventional food or as a sole item of a meal or of the diet. In addition, a dietary supplement cannot be approved or authorized for investigation as a new drug, antibiotic, or biologic, unless it was marketed as a food or a dietary supplement before such approval or authorization. Under DSHEA, dietary supplements are deemed to be food, except for purposes of the drug definition."[9]
Per DSHEA, dietary supplements are consumed orally, and are mainly defined by what they are not: conventional foods (including meal replacements), medical foods,[10] preservatives or pharmaceutical drugs. Products intended for use as a nasal spray, or topically, as a lotion applied to the skin, do not qualify. FDA-approved drugs cannot be ingredients in dietary supplements. Supplement products are or contain vitamins, nutritionally essential minerals, amino acids, essential fatty acids and non-nutrient substances extracted from plants or animals or fungi or bacteria, or in the instance of probiotics, are live bacteria. Dietary supplement ingredients may also be synthetic copies of naturally occurring substances (for example: melatonin). All products with these ingredients are required to be labeled as dietary supplements.[11] Like foods and unlike drugs, no government approval is required to make or sell dietary supplements; the manufacturer confirms the safety of dietary supplements but the government does not; and rather than requiring risk–benefit analysis to prove that the product can be sold like a drug, such assessment is only used by the FDA to decide that a dietary supplement is unsafe and should be removed from market.[11]
Types
Vitamins
Main article: Vitamin
Pharmacies and supermarkets in the U.S. sell a large variety of vitamin dietary supplements.
A vitamin is an organic compound required by an organism as a vital nutrient in limited amounts.[12] An organic chemical compound (or related set of compounds) is called a vitamin when it cannot be synthesized in sufficient quantities by an organism and must be obtained from the diet. The term is conditional both on the circumstances and on the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for anthropoid primates, humans, guinea pigs and bats, but not for other mammals. Vitamin D is not an essential nutrient for people who get sufficient exposure to ultraviolet light, either from the sun or an artificial source, as they synthesize vitamin D in skin.[13] Humans require thirteen vitamins in their diet, most of which are actually groups of related molecules, "vitamers", (e.g. vitamin E includes tocopherols and tocotrienols, vitamin K includes vitamin K1 and K2). The list: vitamins A, C, D, E, K, Thiamine (B1), Riboflavin (B2), Niacin (B3), Pantothenic Acid (B5), Vitamin B6, Biotin (B7), Folate (B9) and Vitamin B12. Vitamin intake below recommended amounts can result in signs and symptoms associated with vitamin deficiency. There is little evidence of benefit when vitamins are consumed as a dietary supplement by those who are healthy and have a nutritionally adequate diet.[14]
The U.S. Institute of Medicine sets tolerable upper intake levels (ULs) for some of the vitamins. This does not prevent dietary supplement companies from selling products with content per serving higher than the ULs. For example, the UL for vitamin D is 100 μg (4,000 IU),[15] but products are available without prescription at 10,000 IU.
Minerals
Main article: Mineral (nutrient)
Minerals are the exogenous chemical elements indispensable for life. Four minerals – carbon, hydrogen, oxygen, and nitrogen – are essential for life but are so ubiquitous in food and drink that these are not considered nutrients and there are no recommended intakes for these as minerals. The need for nitrogen is addressed by requirements set for protein, which is composed of nitrogen-containing amino acids. Sulfur is essential, but for humans, not identified as having a recommended intake per se. Instead, recommended intakes are identified for the sulfur-containing amino acids methionine and cysteine. There are dietary supplements that provide sulfur, such as taurine and methylsulfonylmethane.
The essential nutrient minerals for humans, listed in order by weight needed to be at the Recommended Dietary Allowance or Adequate Intake are potassium, chlorine, sodium, calcium, phosphorus, magnesium, iron, zinc, manganese, copper, iodine, chromium, molybdenum, selenium and cobalt (the last as a component of vitamin B12). There are other minerals which are essential for some plants and animals, but may or may not be essential for humans, such as boron and silicon. Essential and purportedly essential minerals are marketed as dietary supplements, individually and in combination with vitamins and other minerals.
Although as a general rule, dietary supplement labeling and marketing are not allowed to make disease prevention or treatment claims, the U.S. FDA has for some foods and dietary supplements reviewed the science, concluded that there is significant scientific agreement, and published specifically worded allowed health claims. An initial ruling allowing a health claim for calcium dietary supplements and osteoporosis was later amended to include calcium supplements with or without vitamin D, effective January 1, 2010. Examples of allowed wording are shown below. In order to qualify for the calcium health claim, a dietary supplement must contain at least 20% of the Reference Dietary Intake, which for calcium means at least 260 mg/serving.[16]
"Adequate calcium throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis."
"Adequate calcium as part of a healthful diet, along with physical activity, may reduce the risk of osteoporosis in later life."
"Adequate calcium and vitamin D throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis."
"Adequate calcium and vitamin D as part of a healthful diet, along with physical activity, may reduce the risk of osteoporosis in later life."
In the same year, the European Food Safety Authority also approved a dietary supplement health claim for calcium and vitamin D and the reduction of the risk of osteoporotic fractures by reducing bone loss.[17] The U.S. FDA also approved Qualified Health Claims (QHCs) for various health conditions for calcium, selenium and chromium picolinate.[18] QHCs are supported by scientific evidence, but do not meet the more rigorous "significant scientific agreement" standard required for an authorized health claim. If dietary supplement companies choose to make such a claim then the FDA stipulates the exact wording of the QHC to be used on labels and in marketing materials. The wording can be onerous: "One study suggests that selenium intake may reduce the risk of bladder cancer in women. However, one smaller study showed no reduction in risk. Based on these studies, FDA concludes that it is highly uncertain that selenium supplements reduce the risk of bladder cancer in women."[19]
Proteins and amino acids
Main articles: Protein (nutrient) and Amino acid
Protein-containing supplements, either ready-to-drink or as powders to be mixed into water, are marketed as aids to people recovering from illness or injury, those hoping to thwart the sarcopenia of old age,[20][21] to athletes who believe that strenuous physical activity increases protein requirements,[22] to people hoping to lose weight while minimizing muscle loss, i.e., conducting a protein-sparing modified fast,[23] and to people who want to increase muscle size for performance and appearance. Whey protein is a popular ingredient,[21][24][25] but products may also incorporate casein, soy, pea, hemp or rice protein. A meta-analysis found a moderate degree of evidence in favor of whey protein supplements use as a safe and effective adjunct to an athlete's training and recovery, including benefits for endurance, average power, muscle mass, and reduced perceived exercise intensity.[26]
According to US and Canadian Dietary Reference Intake guidelines, the protein Recommended Dietary Allowance (RDA) for adults is based on 0.8 grams protein per kilogram body weight. The recommendation is for sedentary and lightly active people.[27][28][29] Scientific reviews can conclude that a high protein diet, when combined with exercise, will increase muscle mass and strength,[30][31][32] or conclude the opposite.[33] The International Olympic Committee recommends protein intake targets for both strength and endurance athletes at about 1.2–1.8 g/kg body mass per day.[22] One review proposed a maximum daily protein intake of approximately 25% of energy requirements, i.e., approximately 2.0 to 2.5 g/kg.[28]
The same protein ingredients marketed as dietary supplements can be incorporated into meal replacement and medical food products, but those are regulated and labeled differently from supplements. In the United States, "meal replacement" products are foods and are labeled as such. These typically contain protein, carbohydrates, fats, vitamins and minerals. There may be content claims such as "good source of protein", "low fat" or "lactose free".[34] Medical foods, also nutritionally complete, are designed to be used while a person is under the care of a physician or other licensed healthcare professional.[35][10] Liquid medical food products – for example, Ensure – are available in regular and high protein versions.
Proteins are chains of amino acids. Nine of these proteinogenic amino acids are considered essential for humans because they cannot be produced from other compounds by the human body and so must be taken in as food. Recommended intakes, expressed as milligrams per kilogram of body weight per day, have been established.[27] Other amino acids may be conditionally essential for certain ages or medical conditions. Amino acids, individually and in combinations, are sold as dietary supplements. The claim for supplementing with the branched-chain amino acids leucine, valine and isoleucine is for stimulating muscle protein synthesis. A review of the literature concluded this claim was unwarranted.[36] In elderly people, supplementation with just leucine resulted in a modest (0.99 kg) increase in lean body mass.[37] The non-essential amino acid arginine, consumed in sufficient amounts, is thought to act as a donor for the synthesis of nitric oxide, a vasodilator. A review confirmed blood pressure lowering.[38] Taurine, a popular dietary supplement ingredient with claims made for sports performance, is technically not an amino acid. It is synthesized in the body from the amino acid cysteine.[39]
Bodybuilding supplements
This section is an excerpt from Bodybuilding supplement.[edit]
Bodybuilding supplements are dietary supplements commonly used by those involved in bodybuilding, weightlifting, mixed martial arts, and athletics for the purpose of facilitating an increase in lean body mass. Bodybuilding supplements may contain ingredients that are advertised to increase a person's muscle, body weight, athletic performance, and decrease a person's percent body fat for desired muscle definition. Among the most widely used are high protein drinks, pre-workout blends, branched-chain amino acids (BCAA), glutamine, arginine, essential fatty acids, creatine, HMB, whey protein, ZMA, and weight loss products.[40][41] Supplements are sold either as single ingredient preparations or in the form of "stacks" – proprietary blends of various supplements marketed as offering synergistic advantages.
Essential fatty acids
Main article: Essential fatty acids
Fish oil is a commonly used fatty acid supplement because it is a source of omega-3 fatty acids.[42] Fatty acids are strings of carbon atoms, having a range of lengths. If links are all single (C−C), then the fatty acid is called saturated; with one double bond (C=C), it is called monounsaturated; if there are two or more double bonds (C=C=C), it is called polyunsaturated. Only two fatty acids, both polyunsaturated, are considered essential to be obtained from the diet, as the others are synthesized in the body. The "essential" fatty acids are alpha-linolenic acid (ALA), an omega-3 fatty acid, and linoleic acid (LA), an omega-6 fatty acid.[42][43] ALA can be elongated in the body to create other omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Plant oils, particularly seed and nut oils, contain ALA.[42] Food sources of EPA and DHA are oceanic fish, whereas dietary supplement sources include fish oil, krill oil and marine algae extracts. The European Food Safety Authority (EFSA) identifies 250 mg/day for a combined total of EPA and DHA as Adequate Intake, with a recommendation that women pregnant or lactating consume an additional 100 to 200 mg/day of DHA.[44] In the United States and Canada are Adequate Intakes for ALA and LA over various stages of life, but there are no intake levels specified for EPA and/or DHA.[45]
Supplementation with EPA and/or DHA does not appear to affect the risk of death, cancer or heart disease.[46][47] Furthermore, studies of fish oil supplements have failed to support claims of preventing heart attacks or strokes.[48] In 2017, the American Heart Association issued a science advisory stating that it could not recommend use of omega-3 fish oil supplements for primary prevention of cardiovascular disease or stroke, although it reaffirmed supplementation for people who have a history of coronary heart disease.[49]
Manufacturers have begun to include long chain polyunsaturated fatty acids DHA and arachidonic acid (AA) into their formula milk for newborns, however, a 2017 review found that supplementation with DHA and AA does not appear to be harmful or beneficial to formula-fed infants.[50]
Natural products
Main article: Natural product
See also: Phytochemical, Herbalism, and Traditional Chinese medicine
St. John's wort petals used in natural product supplements
Dietary supplements can be manufactured using intact sources or extracts from plants, animals, algae, fungi or lichens, including such examples as ginkgo biloba, curcumin, cranberry, St. John's wort, ginseng, resveratrol, glucosamine and collagen.[51][52][53] Products bearing promotional claims of health benefits are sold without requiring a prescription in pharmacies, supermarkets, specialist shops, military commissaries, buyers clubs, direct selling organizations, and the internet.[52] While most of these products have a long history of use in herbalism and various forms of traditional medicine, concerns exist about their actual efficacy, safety and consistency of quality.[54][55][56] Canada has published a manufacturer and consumer guide describing quality, licensing, standards, identities, and common contaminants of natural products.[57]
In 2019, sales of herbal supplements just in the United States alone were $9.6 billion, with the market growing at approximately 8.6% per year,[58] with cannabidiol and mushroom product sales as the highest.[59] Italy, Germany, and Eastern European countries were leading consumers of botanical supplements in 2016, with European Union market growth forecast to be $8.7 billion by 2020.[60]
Probiotics
Main article: Probiotic
Claimed benefits of using probiotic supplements are not supported by sufficient clinical evidence.[61][62][63] Meta-analysis studies have reported a modest reduction of antibiotic-associated diarrhea and acute diarrhea in children taking probiotics.[64] There is limited evidence in support of adults using mono-strain and multi-strain containing probiotics for the alleviation of symptoms associated with irritable bowel syndrome.[65] Probiotic supplements are generally regarded as safe.[66]
Fertility
Main article: Fertility
A meta-analysis provided preliminary evidence that men treated with supplements containing selenium, zinc, omega-3 fatty acids, coenzyme Q10 or carnitines reported improvements in total sperm count, concentration, motility, and morphology.[67] A review concluded that omega-3 taken through supplements and diet might improve semen quality in infertile men.[68] A 2021 review also supported selenium, zinc, omega-3 fatty acids, coenzyme Q10 or carnitines, but warned that "excessive use of antioxidants may be detrimental to the spermatic function and many of the over-the-counter supplements are not scientifically proven to improve fertility."[69]
There is low quality and insufficient evidence for the use of oral antioxidant supplements as a viable treatment for subfertile woman.[70] A review provided evidence that taking dehydroepiandrosterone before starting an in vitro fertilization series may increase pregnancy rates and decrease miscarriage likelihood.[71]
Prenatal
Main article: Prenatal vitamins
Prenatal vitamins are dietary supplements commonly given to pregnant women to supply nutrients that may reduce health complications for the mother and fetus. Although prenatal vitamins are not meant to substitute for dietary nutrition, prenatal supplementation may be beneficial for pregnant women at risk of nutrient deficiencies because of diet limitations or restrictions. The most common components in prenatal vitamins include vitamins B6, folate, B12, C, D, E, iron and calcium.[72]
Sufficient intake of vitamin B6 can lower the risk of early pregnancy loss and relieve symptoms of morning sickness.[73][74] Folate is also an essential nutrient for pregnant women to prevent neural tube defects.[73] In 2006, the World Health Organization endorsed the recommendation for women of child-bearing age to consume 400 micrograms of folate through the diet daily if planning a pregnancy.[75] A 2013 review found folic acid supplementation during pregnancy did not affect the mother's health other than a risk reduction on low pre-delivery serum folate and megaloblastic anemia.[76] There is little evidence to suggest that vitamin D supplementation improves prenatal outcomes in hypertensive disorders and gestational diabetes.[77][78] Evidence does not support the routine use of vitamin E supplementation during pregnancy to prevent adverse events, such as preterm birth, fetal or neonatal death, or maternal hypertensive disorders.[79][80]
Iron supplementation can lower the risk of iron deficiency anemia for pregnant women.[81] In 2020, the World Health Organization updated recommendations for adequate calcium levels during pregnancy to prevent hypertensive disorders.[82][83]
Pharmacotherapy
Individuals with hypokalemic sensory overstimulation are sometimes diagnosed as having attention deficit hyperactivity disorder (ADHD), raising the possibility that a subtype of ADHD has a cause that can be understood mechanistically and treated in a novel way. The sensory overload is treatable with oral potassium gluconate.
Industry
In 2020, the American market for dietary supplements was valued at $140.3 billion,[4] with the economic impact in the United States for 2016 estimated at $122 billion, including employment wages and taxes.[84] A 2020 analysis projected that the global market for vitamins and dietary supplement products would reach $196.6 billion by 2028, where the growth in market size is largely attributed to recent technological advancements in product manufacturing, increased demand for products advertised as healthy, increased product availability, and population aging.[85]
Adulteration, contamination and mislabeling
Over the period 2008 to 2011, the Government Accountability Office (GAO) of the United States received 6,307 reports of health problems (identified as adverse events) from use of dietary supplements containing a combination of ingredients in manufactured vitamins, minerals or other supplement products,[86] with 92% of tested herbal supplements containing lead and 80% containing other chemical contaminants.[87] Using undercover staff, the GAO also found that supplement retailers intentionally engaged in "unequivocal deception" to sell products advertised with baseless health claims, particularly to elderly consumers.[87] Consumer Reports also reported unsafe levels of arsenic, cadmium, lead and mercury in several protein powder products.[88] The Canadian Broadcasting Corporation (CBC) reported that protein spiking, i.e., the addition of amino acids to manipulate protein content analysis, was common.[89] Many of the companies involved challenged CBC's claim.[90]
A 2013 study on herbal supplements found that many products were of low quality, one third did not contain the active ingredient(s) claimed, and one third contained unlisted substances.[91] In a genetic analysis of herbal supplements, 78% of samples contained animal DNA that was not identified as an ingredient on the product labels.[55] In some botanical products, undeclared ingredients were used to increase the bulk of the product and reduce its cost of manufacturing, while potentially violating certain religious and/or cultural limitations on consuming animal ingredients, such as cow, buffalo or deer.[55] In 2015, the New York Attorney General (NY-AG) identified four major retailers with dietary supplement products that contained fraudulent and potentially dangerous ingredients, requiring the companies to remove the products from retail stores.[92] According to the NY-AG, only about 20% of the herbal supplements tested contained the plants claimed.[92] The methodology used by the NY-AG was disputed. The test involves looking for DNA fragments from the plants named as the dietary supplement ingredients in the products. One scientist said that it was possible that the extraction process used to create the supplements removed or destroyed all DNA. This, however, would not explain the presence of DNA from plants such as rice or wheat, that were not listed as ingredients.[92]
A study of dietary supplements sold between 2007 and 2016 identified 776 that contained unlisted pharmaceutical drugs, many of which could interact with other medications and lead to hospitalization.[93] 86% of the adulterated supplements were marketed for weight loss and sexual performance, with many containing prescription erectile dysfunction medication. Muscle building supplements were contaminated with anabolic steroids that can lead to health complications affecting the kidney, the heart, and cause gynecomastia.[94] Multiple bodybuilding products also contained antidepressants and antihistamines. Despite these findings, fewer than half of the adulterated supplements were recalled.[93]
Regulatory compliance
The European Commission has published harmonized rules on supplement products to assure consumers have minimal health risks from using dietary supplements and are not misled by advertising.[95]
In the United States and Canada, dietary supplements are considered a subset of foods, and are regulated accordingly. The U.S. Food and Drug Administration (FDA) monitors supplement products for accuracy in advertising and labeling. Dietary supplements are regulated by the FDA as food products subject to compliance with current Good Manufacturing Practices (CGMP) and labeling with science-based ingredient descriptions and advertising.[96][97] When finding CGMP or advertising violations, FDA warning letters are used to notify manufacturers of impending enforcement action, including search and seizure, injunction, and financial penalties.[98] Examples between 2016 and 2018 of CGMP and advertising violations by dietary supplement manufacturers included several with illegal compositions or advertising of vitamins and minerals.[99][100][101]
The U.S. Federal Trade Commission, which litigates against deceptive advertising in marketed products,[102] established a consumer center to assist reports of false health claims in product advertising for dietary supplements.[103] In 2017, the FTC successfully sued nine manufacturers for deceptive advertising of dietary supplements.[104]
Adverse effects
In the United States, manufacturers of dietary supplements are required to demonstrate safety of their products before approval is granted for commerce.[105] Despite this caution, numerous adverse effects have been reported,[86] including muscle cramps, hair loss, joint pain, liver disease, and allergic reactions, with 29% of the adverse effects resulting in hospitalization, and 20% in serious injuries or illnesses.[86] The potential for adverse effects also occurs when individuals consume more than the necessary daily amount of vitamins or minerals that are needed to maintain normal body processes and functions.[106] The incidence of adverse effects reported to the FDA were due to "combination products" that contain multiple ingredients, whereas dietary supplements containing a single vitamin, mineral, lipid product, and herbal product were less likely to cause adverse effects related to excess supplementation.[86]
Among general reasons for the possible harmful effects of dietary supplements are: a) absorption in a short time, b) manufacturing quality and contamination, and c) enhancing both positive and negative effects at the same time.[56] The incidence of liver injury from herbal and dietary supplements is about 16–20% of all supplement products causing injury, with the occurrence growing globally over the early 21st century.[107] The most common liver injuries from weight loss and bodybuilding supplements involve hepatocellular damage with resulting jaundice, and the most common supplement ingredients attributed to these injuries are green tea catechins, anabolic steroids, and the herbal extract, aegeline.[107] Weight loss supplements have also had adverse psychiatric effects.[108] Some dietary supplements may also have adverse interactions with prescription medications that may enhance side effects or decrease therapeutic effects of medications.[109]
Society and culture
Public health
Work done by scientists in the early 20th century on identifying individual nutrients in food and developing ways to manufacture them raised hopes that optimal health could be achieved and diseases prevented by adding them to food and providing people with dietary supplements; while there were successes in preventing vitamin deficiencies, and preventing conditions like neural tube defects by supplementation and food fortification with folic acid, no targeted supplementation or fortification strategies to prevent major diseases like cancer or cardiovascular diseases have proved successful.[110]
For example, while increased consumption of fruits and vegetables are related to decreases in mortality, cardiovascular diseases and cancers, supplementation with key factors found in fruits and vegetable, like antioxidants, vitamins, or minerals, do not help and some have been found to be harmful in some cases.[111][112] In general, as of 2016, robust clinical data is lacking, that shows that any kind of dietary supplementation does more good than harm for people who are healthy and eating a reasonable diet but there is clear data showing that dietary pattern and lifestyle choices are associated with health outcomes.[113][114]
As a result of the lack of good data for supplementation and the strong data for dietary pattern, public health recommendations for healthy eating urge people to eat a plant-based diet of whole foods, minimizing ultra-processed food, salt and sugar and to get exercise daily, and to abandon Western pattern diets and a sedentary lifestyle.[115][116]: 10
Legal regulation
United States
Main article: Regulation of food and dietary supplements by the U.S. Food and Drug Administration
The regulation of food and dietary supplements by the U.S. Food and Drug Administration (FDA) is governed by various statutes enacted by the United States Congress. Pursuant to the Federal Food, Drug, and Cosmetic Act and accompanying legislation, the FDA has authority to oversee the quality of substances sold as food in the United States, and to monitor claims made in the labeling about both the composition and the health benefits of foods.
Substances which the FDA regulates as food are subdivided into various categories, including foods, food additives, added substances (man-made substances which are not intentionally introduced into food, but nevertheless end up in it), and dietary supplements. The specific standards which the FDA exercises differ from one category to the next. Furthermore, the FDA has been granted a variety of means by which it can address violations of the standards for a given category of substances.
Dietary supplement manufacture is required to comply with the good manufacturing practices established in 2007. The FDA can visit manufacturing facilities, send Warning Letters[100] if not in compliance with GMPs, stop production, and if there is a health risk, require that the company conduct a recall.[117] Only after a dietary supplement product is marketed, may the FDA's Center for Food Safety and Applied Nutrition (CFSAN) review the products for safety and effectiveness.[118]
European Union
The European Union's (EU) Food Supplements Directive of 2002 requires that supplements be demonstrated to be safe, both in dosages and in purity.[119] Only those supplements that have been proven to be safe may be sold in the EU without prescription. As a category of food, food supplements cannot be labeled with drug claims but can bear health claims and nutrition claims.[120]
The dietary supplements industry in the United Kingdom (UK), one of the 28 countries in the bloc, strongly opposed the Directive. In addition, a large number of consumers throughout Europe, including over one million in the UK, and various doctors and scientists, had signed petitions by 2005 against what are viewed by the petitioners as unjustified restrictions of consumer choice.[121] In 2004, along with two British trade associations, the Alliance for Natural Health (ANH) had a legal challenge to the Food Supplements Directive[122] referred to the European Court of Justice by the High Court in London.[123]
Although the European Court of Justice's Advocate General subsequently said that the bloc's plan to tighten rules on the sale of vitamins and food supplements should be scrapped,[124] he was eventually overruled by the European Court, which decided that the measures in question were necessary and appropriate for the purpose of protecting public health. ANH, however, interpreted the ban as applying only to synthetically produced supplements, and not to vitamins and minerals normally found in or consumed as part of the diet.[125] Nevertheless, the European judges acknowledged the Advocate General's concerns, stating that there must be clear procedures to allow substances to be added to the permitted list based on scientific evidence. They also said that any refusal to add the product to the list must be open to challenge in the courts.[126]
Fraudulent products during the COVID-19 outbreak
During the COVID-19 pandemic in the United States, the FDA and Federal Trade Commission (FTC) warned consumers about marketing scams of fraudulent supplement products, including homeopathic remedies, cannabidiol products, teas, essential oils, tinctures and colloidal silver, among others.[127][128] By August 2020, the FDA and FTC had issued warning letters to dozens of companies advertising scam products, which were purported "to be drugs, medical devices or vaccines. Products that claim to cure, mitigate, treat, diagnose or prevent disease, but are not proven safe and effective for those purposes, defraud consumers of money and can place consumers at risk for serious harm"[127][129][130]
Research
Examples of ongoing government research organizations to better understand the potential health properties and safety of dietary supplements are the European Food Safety Authority,[3] the Office of Dietary Supplements of the United States National Institutes of Health,[7][131] the Natural and Non-prescription Health Products Directorate of Canada,[132] and the Therapeutic Goods Administration of Australia.[133] Together with public and private research groups, these agencies construct databases on supplement properties, perform research on quality, safety, and population trends of supplement use, and evaluate the potential clinical efficacy of supplements for maintaining health or lowering disease risk.[131]
Databases
As continual research on the properties of supplements accumulates, databases or fact sheets for various supplements are updated regularly, including the Dietary Supplement Label Database,[5] Dietary Supplement Ingredient Database,[134] and Dietary Supplement Facts Sheets of the United States.[135] In Canada where a license is issued when a supplement product has been proven by the manufacturer and government to be safe, effective and of sufficient quality for its recommended use, an eight-digit Natural Product Number is assigned and recorded in a Licensed Natural Health Products Database.[136] The European Food Safety Authority maintains a compendium of botanical ingredients used in manufacturing of dietary supplements.[137]
In 2015, the Australian Government's Department of Health published the results of a review of herbal supplements to determine if any were suitable for coverage by health insurance.[138] Establishing guidelines to assess safety and efficacy of botanical supplement products, the European Medicines Agency provided criteria for evaluating and grading the quality of clinical research in preparing monographs about herbal supplements.[139] In the United States, the National Center for Complementary and Integrative Health of the National Institutes of Health provides fact sheets evaluating the safety, potential effectiveness and side effects of many botanical products.[140]
Quality and safety
To assure supplements have sufficient quality, standardization, and safety for public consumption, research efforts have focused on development of reference materials for supplement manufacturing and monitoring.[137][141] High-dose products have received research attention,[131][142] especially for emergency situations such as vitamin A deficiency in malnutrition of children,[143] and for women taking folate supplements to reduce the risk of breast cancer.[144]
Population monitoring
In the United States, the National Health and Nutrition Examination Survey (NHANES) has investigated habits of using dietary supplements in context of total nutrient intakes from the diet in adults and children.[131] Over the period of 1999 to 2012, use of multivitamins decreased, and there was wide variability in the use of individual supplements among subgroups by age, sex, race/ethnicity, and educational status.[145] Particular attention has been given to use of folate supplements by young women to reduce the risk of fetal neural tube defects.[146][147]
Clinical studies
Limited human research has been conducted on the potential for dietary supplementation to affect disease risk. Examples:
vitamin D – acute respiratory tract infections[148]
iron – maternal iron deficiency anemia and adverse effects on the fetus[149]
multiple supplements – no evidence of benefit to lower risk of death, cardiovascular diseases or cancer[150]
magnesium supplementation – in reducing all-cause and cancer mortality,[151] as well as improving glucose parameters in people with diabetes and insulin-sensitivity parameters in those at high risk of diabetes.[152]
folate alone or with B vitamins – stroke[153][154]
A 2017 academic review indicated a rising incidence of liver injury from use of herbal and dietary supplements, particularly those with steroids, green tea extract, or multiple ingredients.[107]
Absence of benefit
The potential benefit of using essential nutrient dietary supplements to lower the risk of diseases has been refuted by findings of no effect or weak evidence in numerous clinical reviews, such as for HIV,[155] or tuberculosis.[156]
Reporting bias
A review of clinical trials registered at clinicaltrials.gov, which would include both drugs and supplements, reported that nearly half of completed trials were sponsored wholly or partially by industry.[157] This does not automatically imply bias, but there is evidence that because of selective non-reporting, results in support of a potential drug or supplement ingredient are more likely to be published than results that do not demonstrate a statistically significant benefit.[157][158] One review reported that fewer than half of the registered clinical trials resulted in publication in peer-reviewed journals.[159]
Future
Improving public information about use of dietary supplements involves investments in professional training programs, further studies of population and nutrient needs, expanding the database information, enhancing collaborations between governments and universities, and translating dietary supplement research into useful information for consumers, health professionals, scientists, and policymakers.[160] Future demonstration of efficacy from use of dietary supplements requires high-quality clinical research using rigorously qualified products and compliance with established guidelines for reporting of clinical trial results (e.g., CONSORT guidelines).[131]
See also
multivitamin is a preparation intended to serve as a dietary supplement with vitamins, dietary minerals, and other nutritional elements. Such preparations are available in the form of tablets, capsules, pastilles, powders, liquids, or injectable formulations. Other than injectable formulations, which are only available and administered under medical supervision, multivitamins are recognized by the Codex Alimentarius Commission (the United Nations' authority on food standards) as a category of food.[1]
In healthy people, most scientific evidence indicates that multivitamin supplements do not prevent cancer, heart disease, or other ailments, and regular supplementation is not necessary.[2][3][4][5][6][7][8] However, specific groups of people may benefit from multivitamin supplements, for example, people with poor nutrition or those at high risk of macular degeneration.[3][9]
There is no standardized scientific definition for multivitamin.[10] In the United States, a multivitamin/mineral supplement is defined as a supplement containing three or more vitamins and minerals that does not include herbs, hormones, or drugs, where each vitamin and mineral is included at a dose below the tolerable upper intake level as determined by the Food and Drug Board, and does not present a risk of adverse health effects.[11]
Products and components
Many multivitamin formulas contain vitamin C, B1, B2, B3, B5, B6, B7, B9, B12, A, E, D2 (or D3), K, potassium, iodine, selenium, borate, zinc, calcium, magnesium, manganese, molybdenum, beta carotene, and/or iron. Multivitamins are typically available in a variety of formulas based on age and sex, or (as in prenatal vitamins) based on more specific nutritional needs; a multivitamin for men might include less iron, while a multivitamin for seniors might include extra vitamin D. Some formulas make a point of including extra antioxidants.
Some nutrients, such as calcium and magnesium, are rarely included at 100% of the recommended allowance because the pill would become too large in size. Most multivitamins come in capsule form; tablets, powders, liquids, and injectable formulations also exist. In the United States, the FDA requires any product marketed as a "multivitamin" to contain at least three vitamins and minerals; furthermore, the dosages must be below a "tolerable upper limit", and a multivitamin may not include herbs, hormones, or drugs.[12]
Uses
For certain people, particularly for older people, supplementing the diet with additional vitamins and minerals can have health impacts; however, the majority will not benefit.[13] People with dietary imbalances may include those on restrictive diets and those who cannot or will not eat a nutritious diet. Pregnant women and elderly adults have different nutritional needs compared to other adults, and a multivitamin may be indicated by a physician. Generally, medical advice is to avoid multivitamins during pregnancy, particularly those containing vitamin A, unless they are recommended by a health care professional. However, the NHS recommends 10μg of Vitamin D per day throughout the pregnancy and while breastfeeding, and 400μg of folic acid during the first trimester (first 12 weeks of pregnancy).[14] Some women may need to take iron, vitamin C, or calcium supplements during pregnancy, but only on the advice of a doctor.
In the 1999–2000 National Health and Nutrition Examination Survey, 52% of adults in the United States reported taking at least one dietary supplement in the last month and 35% reported regular use of multivitamin-multimineral supplements. Women versus men, older adults versus younger adults, non-Hispanic whites versus non-Hispanic blacks, and those with higher education levels versus lower education levels (among other categories) were more likely to take multivitamins. Individuals who use dietary supplements (including multivitamins) generally report higher dietary nutrient intakes and healthier diets. Additionally, adults with a history of prostate and breast cancers were more likely to use dietary and multivitamin supplements.[15]
Precautions
The amounts of each vitamin type in multivitamin formulations are generally adapted to correlate with what is believed to result in optimal health effects in large population groups. However, these standard amounts may not correlate with what is optimal in certain subpopulations, such as in children, pregnant women and people with certain medical conditions and medication.
The health benefit of vitamins generally follows a biphasic dose-response curve, taking the shape of a bell curve, with the area in the middle being the safe-intake range and the edges representing deficiency and toxicity.[16] For example, the Food and Drug Administration recommends that adults on a 2,000 calorie diet get between 60 and 90 milligrams of vitamin C per day.[17] This is the middle of the bell curve. The upper limit is 2,000 milligrams per day for adults, which is considered potentially dangerous.[18]
In particular, pregnant women should consult their doctors before taking any multivitamins. For example, either an excess or deficiency of vitamin A can cause birth defects.[19]
Long-term use of beta-carotene, vitamin A, and vitamin E supplements may shorten life,[2] and increase the risk of lung cancer in people who smoke (especially those smoking more than 20 cigarettes per day), former smokers, people exposed to asbestos, and those who use alcohol.[20] Many common brand supplements in the United States contain levels above the DRI/RDA amounts for some vitamins or minerals.
Severe vitamin and mineral deficiencies require medical treatment and can be very difficult to treat with common over-the-counter multivitamins. In such situations, special vitamin or mineral forms with much higher potencies are available, either as individual components or as specialized formulations.
Multivitamins in large quantities may pose a risk of an acute overdose due to the toxicity of some components, principally iron. However, in contrast to iron tablets, which can be lethal to children,[21] toxicity from overdoses of multivitamins are very rare.[22] There appears to be little risk to supplement users of experiencing acute side effects due to excessive intakes of micronutrients.[23] There also are strict limits on the retinol content for vitamin A during pregnancies that are specifically addressed by prenatal formulas.
As noted in dietary guidelines from Harvard School of Public Health in 2008, multivitamins should not replace healthy eating or make up for unhealthy eating.[24][failed verification] In 2015, the U.S. Preventive Services Task Force analyzed studies that included data for about 450,000 people. The analysis found no clear evidence that multivitamins prevent cancer or heart disease, helped people live longer, or "made them healthier in any way."[25]
Research
Provided that precautions are taken (such as adjusting the vitamin amounts to what is believed to be appropriate for children, pregnant women or people with certain medical conditions), multivitamin intake is generally safe, but research is still ongoing with regard to what health effects multivitamins have.
Evidence of health effects of multivitamins comes largely from prospective cohort studies, which evaluate health differences between groups that take multivitamins and groups that do not. Correlations between multivitamin intake and health found by such studies may not result from multivitamins themselves, but may reflect underlying characteristics of multivitamin-takers. For example, it has been suggested that multivitamin-takers may, overall, have more underlying diseases (making multivitamins appear as less beneficial in prospective cohort studies).[26] On the other hand, it has also been suggested that multivitamin users may, overall, be more health-conscious (making multivitamins appear as more beneficial in prospective cohort studies).[27][28] Randomized controlled studies have been encouraged to address this uncertainty.[29]
Cohort studies
Centrum multivitamins produced by Pfizer, which were used in Physicians' Health Study II
In February 2009, a study conducted in 161,808 postmenopausal women from the Women's Health Initiative clinical trials concluded that after eight years of follow-up "multivitamin use has little or no influence on the risk of common cancers, cardiovascular disease, or total mortality".[28] Another 2010 study in the Journal of Clinical Oncology suggested that multivitamin use during chemotherapy for stage III colon cancer had no effect on the outcomes of treatment.[30] A very large prospective cohort study published in 2011, including more than 180,000 participants, found no significant association between multivitamin use and mortality from all causes. The study also found no impact of multivitamin use on the risk of cardiovascular disease or cancer.[31]
A cohort study that received widespread media attention[32][33] is the Physicians' Health Study II (PHS-II).[34] PHS-II was a double-blind study of 14,641 male U.S. physicians initially aged 50 years or older (mean age of 64.3) that ran from 1997 to June 1, 2011. The mean time that the men were followed was 11 years. The study compared total cancer (excluding non-melanoma skin cancer) for participants taking a daily multivitamin (Centrum Silver by Pfizer) versus a placebo. Compared with the placebo, men taking a daily multivitamin had a small but statistically significant reduction in their total incidence of cancer. In absolute terms, the difference was just 1.3 cancer diagnoses per 1000 years of life. The hazard ratio for cancer diagnosis was 0.92 with a 95% confidence interval spanning 0.86–0.998 (P = .04); this implies a benefit of between 14% and .2% over placebo in the confidence interval. No statistically significant effects were found for any specific cancers or for cancer mortality. As pointed out in an editorial in the same issue of the Journal of the American Medical Association, the investigators observed no difference in the effect whether the study participants were or were not adherent to the multivitamin intervention, which diminishes the dose–response relationship.[35] The same editorial argued that the study did not properly address the multiple comparisons problem, in that the authors neglected to fully analyze all 28 possible associations in the study—they argue if this had been done, the statistical significance of the results would be lost.[35]
Using the same PHS-II study, researchers concluded that taking a daily multivitamin did not have any effect in reducing heart attacks and other major cardiovascular events, MI, stroke, and CVD mortality.[36]
Systematic reviews and meta-analyses
One major meta-analysis published in 2011, including previous cohort and case-control studies, concluded that multivitamin use was not significantly associated with the risk of breast cancer. It noted that one Swedish cohort study has indicated such an effect, but with all studies taken together, the association was not statistically significant.[29] A 2012 meta-analysis of ten randomized, placebo-controlled trials published in the Journal of Alzheimer's Disease found that a daily multivitamin may improve immediate recall memory, but did not affect any other measure of cognitive function.[37]
Another meta-analysis, published in 2013, found that multivitamin-multimineral treatment "has no effect on mortality risk",[38] and a 2013 systematic review found that multivitamin supplementation did not increase mortality and might slightly decrease it.[39] A 2014 meta-analysis reported that there was "sufficient evidence to support the role of dietary multivitamin/mineral supplements for the decreasing the risk of age-related cataracts."[40] A 2015 meta-analysis argued that the positive result regarding the effect of vitamins on cancer incidence found in Physicians' Health Study II (discussed above) should not be overlooked despite the neutral results found in other studies.
Looking at 2012 data, a study published in 2018 presented meta-analyses on cardiovascular disease outcomes and all-cause mortality. It found that "conclusive evidence for the benefit of any supplement across all dietary backgrounds (including deficiency and sufficiency) was not demonstrated; therefore, any benefits seen must be balanced against possible risks." The study dismissed the benefits of routinely taking supplements of vitamins C and D, beta-carotene, calcium, and selenium. Results indicated taking niacin may actually be harmful.[4][5]
In July 2019, another meta-analysis of 24 interventions in 277 trials was conducted and published in Annals of Internal Medicine, including a total of almost 1,000,000 participants.[7] The study generally concluded that the vast majority of multivitamins had no significant effect on survival or heart attack risk.[41] The study found a significant effect on heart health in a low-salt diet, and a small effect due to omega-3 and folic acid supplements.[42] This analysis supports the results of two early 2018 studies that found no conclusive benefits from multivitamins for healthy adults.[6][43]
Expert bodies
A 2006 report by the U.S. Agency for Healthcare Research and Quality concluded that "regular supplementation with a single nutrient or a mixture of nutrients for years has no significant benefits in the primary prevention of cancer, cardiovascular disease, cataract, age-related macular degeneration or cognitive decline."[9] However, the report noted that multivitamins have beneficial effects for certain sub-populations, such as people with poor nutritional status, that vitamin D and calcium can help prevent fractures in older people, and that zinc and antioxidants can help prevent age-related macular degeneration in high-risk individuals.[9] A 2017 Cochrane Systematic Review found that multivitamins including vitamin E or beta carotene will not delay the onset of macular degeneration or prevent the disease,[44] however, some people with macular degeneration may benefit from multivitamin supplementation as there is evidence that it may delay the progression of the disease.[45] Including lutein and zeaxanthin supplements in with a multivitamin does not improve progression of macular degeneration.[45] The need for high-quality studies looking at the safety of taking multivitamins has been highlighted.[45]
According to the Harvard School of Public Health: "... many people don't eat the healthiest of diets. That's why a multivitamin can help fill in the gaps, and may have added health benefits."[46] The U.S. Office of Dietary Supplements, a branch of the National Institutes of Health, suggests that multivitamin supplements might be helpful for some people with specific health problems (for example, macular degeneration). However, the Office concluded that "most research shows that healthy people who take an MVM [multivitamin] do not have a lower chance of diseases, such as cancer, heart disease, or diabetes. Based on current research, it's not possible to recommend for or against the use of MVMs to stay healthier longer."[3]
Regulations
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This section needs expansion. You can help by adding to it. (March 2009)
United States
The first person to formulate vitamins in the US was Dr. Forrest C. Shaklee.[47] Shaklee introduced a product he dubbed "Shaklee's Vitalized Minerals" in 1915, which he sold until adopting the now ubiquitous term "vitamin" in 1929.[48]
Because of their categorization as a dietary supplement by the Food and Drug Administration (FDA), most multivitamins sold in the U.S. are not required to undergo the testing procedures typical of pharmaceutical drugs. However, some multivitamins contain very high doses of one or several vitamins or minerals, or are specifically intended to treat, cure, or prevent disease, and therefore require a prescription or medicinal license in the U.S. Since such drugs contain no new substances, they do not require the same testing as would be required by a New Drug Application, but were allowed on the market as drugs due to the Drug Efficacy Study Implementation program.[49]
Australia
Vitamins are classed as low-risk medications by the Therapeutic Goods Administration (TGA), and are therefore not assessed for efficacy, unlike most medicines sold in Australia. They require that the product is safe and that claims of efficacy can only be made in regards to minor ailments. No claims can be made about serious conditions. The TGA does not examine the contents of the product and whether it is what the label says it is, but they claim to carry out "targeted and random surveillance of products on the market."[50] They encourage people to report any unsafe products to them.
The TGA, however, has been criticized, by people such as Allan Asher, a regulatory expert and former deputy chair of the Australian Competition & Consumer Commission, for allowing more than a thousand types of claim, 86% of which are not supported by scientific evidence, including "softens hardness", "replenishes gate of vitality" and "moistens dryness in the triple burner".[51]
Psychological resilience is the ability to cope mentally and emotionally with a crisis, or to return to pre-crisis status quickly.[1]
The term was popularized in the 1970s and 1980s by psychologist Emmy Werner as she conducted a forty-year-long study of a cohort of Hawaiian children who came from low socioeconomic status backgrounds.[2]
Numerous factors influence a person's level of resilience. Internal factors include personal characteristics such as self-esteem, self-regulation, and a positive outlook on life. External factors include social support systems, including relationships with family, friends, and community, as well as access to resources and opportunities.[3]
People can leverage psychological interventions and other strategies to enhance their resilience and better cope with adversity.[4] These include cognitive-behavioral techniques, mindfulness practices, building psychosocial factors, fostering positive emotions, and promoting self-compassion.
Overview
A resilient person uses "mental processes and behaviors in promoting personal assets and protecting self from the potential negative effects of stressors".[5] Psychological resilience is an adaptation in a person's psychological traits and experiences that allows them to regain or remain in a healthy mental state during crises/chaos without long-term negative consequences.[6]
It is difficult to measure and test this psychological construct because resilience can be interpreted in a variety of ways. Most psychological paradigms (biomedical, cognitive-behavioral, sociocultural, etc.) have their own perspective of what resilience looks like, where it comes from, and how it can be developed. There are numerous definitions of psychological resilience, most of which center around two concepts: adversity and positive adaptation.[7] Positive emotions, social support, and hardiness can influence a person to become more resilient.[8][9]
A psychologically resilient person can resist adverse mental conditions that are often associated with unfavorable life circumstances. This differs from psychological recovery which is associated with returning to those mental conditions that preceded a traumatic experience or personal loss.[10]
Research on psychological resilience has shown that it plays a crucial role in promoting mental health and well-being. Resilient people are better equipped to navigate life's challenges, maintain positive emotions, and recover from setbacks. They demonstrate higher levels of self-efficacy, optimism, and problem-solving skills, which contribute to their ability to adapt and thrive in adverse situations.[10]
Resilience is a "positive adaptation" after a stressful or adverse situation.[11] When a person is "bombarded by daily stress, it disrupts their internal and external sense of balance, presenting challenges as well as opportunities." The routine stressors of daily life can have positive impacts which promote resilience. Some psychologists believe that it is not stress itself that promotes resilience but rather the person's perception of their stress and of their level of control.[12][page needed] The presence of stress allows people to practice resilience. It is unknown what the correct level of stress is for each person. Some people can handle more stress than others.
Stress is experienced in a person's life course at times of difficult life transitions, involving developmental and social change; traumatic life events, including grief and loss; and environmental pressures, encompassing poverty and community violence.[13]
Resilience is the integrated adaptation of physical, mental, and spiritual aspects to circumstances, and a coherent sense of self that is able to maintain normative developmental tasks that occur at various stages of life.[14] The Children's Institute of the University of Rochester explains that "resilience research is focused on studying those who engage in life with hope and humor despite devastating losses".[15]
Resilience is not only about overcoming a deeply stressful situation, but also coming out of such a situation with "competent functioning". Resiliency allows a person to rebound from adversity as a strengthened and more resourceful person.[14]
Some characteristics associated with psychological resilience include: an easy temperament, good self-esteem, planning skills, and a supportive environment inside and outside of the family.[7]
When an event is appraised as comprehensible (predictable), manageable (controllable), and somehow meaningful (explainable) a resilient response is more likely.[16]
Process
Psychological resilience is commonly understood as a process. It can also be characterized as a tool a person develops over time, or as a personal trait of the person ("resiliency").[17] Most research shows resilience as the result of people being able to interact with their environments and participate in processes that either promote well-being or protect them against the overwhelming influence of relative risk.[18] This research supports the model in which psychological resilience is seen as a process rather than a trait—something to develop or pursue, rather than a static endowment or endpoint.[19]
Ray Williams believes that there are three basic ways people may react when faced with a difficult situation.[20]
respond with anger or aggression
become overwhelmed and shut down
feel the emotion about the situation and appropriately handle the emotion
He believes the third option helps a person promote wellness and demonstrate resilience. People who take the first or second options tend to label themselves as victims of circumstance or blame others for their misfortune. They do not effectively cope with their environment but become reactive, and they tend to cling to negative emotions. This often makes it difficult to focus on problem solving or to recover. Those who are more resilient respond to their conditions by coping, bouncing back, and looking for a solution. Williams believes that resilience can be aided by supportive social environments (such as families, communities, schools) and social policies.[20]
Resilience can be viewed as a developmental process (the process of developing resilience), or as indicated by a response process.[21] In the latter approach, the effects of an event or stressor on a situationally relevant indicator variable are studied, distinguishing immediate responses, dynamic responses, and recovery patterns.[22] In response to a stressor, more-resilient people show some (but less than less-resilient people) increase in stress. The speed with which this stress response returns to pre-stressor levels is also indicative of a person's resilience.
Biological models
From a scientific standpoint, resilience’s contested definition is multifaceted in relation to genetics, revealing a complex link between biological mechanisms and resilience
"Resilience, conceptualized as a positive bio-psychological adaptation, has proven to be a useful theoretical context for understanding variables for predicting long-term health and well-being".[23]
Three notable bases for resilience—self-confidence, self-esteem and self-concept—each have roots in a different nervous system—respectively, the somatic nervous system, the autonomic nervous system, and the central nervous system.[24]
Research indicates that, like trauma, resilience is influenced by epigenetic modifications. Increased DNA methylation of the growth factor GDNF in certain brain regions promotes stress resilience, as do molecular adaptations of the blood–brain barrier.[25]
The two neurotransmitters primarily responsible for stress buffering within the brain are dopamine and endogenous opioids, as evidenced by research showing that dopamine and opioid antagonists increased stress response in both humans and animals.[26] Primary and secondary rewards[definition needed] reduce negative reactivity[definition needed] of stress in the brain in both humans and animals.[27] The relationship between social support and stress resilience is thought to be mediated by the oxytocin system's impact on the hypothalamic-pituitary-adrenal axis.[28]
Alongside such neurotransmitters, stress-induced alterations in brain structures, such as the prefrontal cortex (PFC) and hippocampus have been linked to mental health issues like depression and anxiety.[29] The increased activation of the medial prefrontal cortex and glutamatergic circuits has emerged as a potential factor in enhancing resilience as “environmental enrichment… increases the complexity of… pyramidal neurons in hippocampus and PFC, suggesting… a shared feature of resilience under these two distinct condition[s]."
History
The first research on resilience was published in 1973. The study used epidemiology—the study of disease prevalence—to uncover the risks and the protective factors that now help define resilience.[30] A year later, the same group of researchers created tools to look at systems that support development of resilience.[31]
Emmy Werner was one of the early scientists to use the term resilience. She studied a cohort of children from Kauai, Hawaii. Kauai was quite poor and many of the children in the study grew up with alcoholic or mentally ill parents. Many of the parents were also out of work.[32] Werner noted that of the children who grew up in these detrimental situations, two-thirds exhibited destructive behaviors in their later-teen years, such as chronic unemployment, substance abuse, and out-of-wedlock births (in girls). However, one-third of these youngsters did not exhibit destructive behaviors. Werner called the latter group resilient.[2] Thus, resilient children and their families were those who, by definition, demonstrated traits that allowed them to be more successful than non-resilient children and families.
Resilience also emerged as a major theoretical and research topic in the 1980s in studies of children with mothers diagnosed with schizophrenia.[33] A 1989 study[34] showed that children with a schizophrenic parent may not obtain an appropriate level of comforting caregiving—compared to children with healthy parents—and that such situations often had a detrimental impact on children's development. On the other hand, some children of ill parents thrived and were competent in academic achievement, which led researchers to make efforts to understand such responses to adversity.
Since the onset of the research on resilience, researchers have been devoted to discovering protective factors that explain people's adaptation to adverse conditions, such as maltreatment,[35] catastrophic life events,[36] or urban poverty.[37] Researchers endeavor to uncover how some factors (e.g. connection to family) may contribute to positive outcomes.[37]
Trait resilience
Temperamental and constitutional disposition is a major factor in resilience. It is one of the necessary precursors of resilience along with warmth in family cohesion and accessibility of prosocial support systems.[38] There are three kinds of temperamental systems that play part in resilience: the appetitive system, defensive system, and attentional system.[39]
Trait resilience is negatively correlated with the personality traits of neuroticism and negative emotionality, which represent tendencies to see and react to the world as threatening, problematic, and distressing, and to view oneself as vulnerable. Trait resilience is positively correlated with the personality traits of openness and positive emotionality, that represent tendencies to engage with and confront the world with confidence in success and a fair value to[clarification needed] self-directedness.[40]
Resilience traits are personal characteristics that express how people approach and react to events that they experience as negative.[41][42] Trait resilience is generally considered via two methods: direct assessment of traits through resilience measures and proxy assessments of resilience in which existing cognate psychological constructs are used to explain resilient outcomes.[43] Typically, trait resilience measures explore how individuals tend to react to and cope with adverse events. Proxy assessments of resilience, sometimes referred to as the buffering approach,[44][45] view resilience as the antithesis of risk, focusing on how psychological processes interrelate with negative events to mitigate their effects. Possibly an individual perseverance trait, conceptually related to persistence and resilience, could also be measured behaviorally by means of arduous, difficult, or otherwise unpleasant tasks.[46]
eveloping and sustaining resilience
There are several theories or models that attempt to describe subcomponents, prerequisites, predictors, or correlates of resilience.
Fletcher and Sarkar found five factors that develop and sustain a person's resilience:[7]
the ability to make realistic plans and being capable of taking the steps necessary to follow through with them
confidence in one's strengths and abilities
communication and problem-solving skills
the ability to manage strong impulses and feelings
having good self-esteem
Among older adults, Kamalpour et al. found that the important factors are external connections, grit, independence, self-care, self-acceptance, altruism, hardship experience, health status, and positive perspective on life.[47]
Another study examined thirteen high-achieving professionals who seek challenging situations that require resilience, all of whom had experienced challenges in the workplace and negative life events over the course of their careers but who had also been recognized for their great achievements in their respective fields. Participants were interviewed about everyday life in the workplace as well as their experiences with resilience and thriving. The study found six main predictors of resilience: positive and proactive personality, experience and learning, sense of control, flexibility and adaptability, balance and perspective, and perceived social support. High achievers were also found to engage in many activities unrelated to their work such as engaging in hobbies, exercising, and organizing meetups with friends and loved ones.[48]
The American Psychological Association, in its popular psychology-oriented Psychology topics publication, suggests the following tactics people can use to build resilience:[49]
Prioritize relationships.
Join a social group.
Take care of your body.
Practice mindfulness.
Avoid negative coping outlets (like alcohol use).
Help others.
Be proactive; search for solutions.
Make progress toward your goals.
Look for opportunities for self-discovery.
Keep things in perspective.
Accept change.
Maintain a hopeful outlook.
Learn from your past.
The idea that one can build one's resilience implies that resilience is a developable characteristic, and so is perhaps at odds with the theory that resilience is a process.[50][51]
Positive emotions
The relationship between positive emotions and resilience has been extensively studied. People who maintain positive emotions while they face adversity are more flexibile in their thinking and problem solving. Positive emotions also help people recover from stressful experiences. People who maintain positive emotions are better-defended from the physiological effects of negative emotions, and are better-equipped to cope adaptively, to build enduring social resources, and to enhance their well-being.[52]
The ability to consciously monitor the factors that influence one's mood is correlated with a positive emotional state.[53] This is not to say that positive emotions are merely a by-product of resilience, but rather that feeling positive emotions during stressful experiences may have adaptive benefits in the coping process.[54] Resilient people who have a propensity for coping strategies that concretely elicit positive emotions—such as benefit-finding and cognitive reappraisal, humor, optimism, and goal-directed problem-focused coping—may strengthen their resistance to stress by allocating more access to these positive emotional resources.[55] Social support from caring adults encouraged resilience among participants by providing them with access to conventional activities.[56][relevant?]
Positive emotions have physiological consequences. For example, humor leads to improvements in immune system functioning and increases in levels of salivary immunoglobulin A, a vital system antibody, which serves as the body's first line of defense in respiratory illnesses.[57] Other health outcomes[clarification needed] include faster injury recovery rate and lower readmission rates to hospitals for the elderly, and reductions in the length of hospital stay.[citation needed] One study has found early indications that older adults who have increased levels of psychological resilience have decreased odds of death or inability to walk after recovering from hip fracture surgery.[58] In another study, trait-resilient individuals experiencing positive emotions more quickly rebounded from cardiovascular activation that was initially generated by negative emotional arousal.[54]
Social support
Social support is an important factor in the development of resilience.[59][60] While many competing definitions of social support exist, they tend to concern one's degree of access to, and use of, strong ties to other people who are similar to oneself.[61] Social support requires solidarity and trust, intimate communication, and mutual obligation[62] both within and outside the family.[60]
Military studies have found that resilience is also dependent on group support: unit
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The mind is what thinks, feels, perceives, imagines, remembers, and wills, encompassing the totality of mental phenomena. It includes both conscious processes, through which an individual is aware of external and internal circumstances, and unconscious processes, which can influence an individual without intention or awareness. Traditionally, minds were often conceived as separate entities that can exist on their own but are more commonly understood as features or capacities of other entities in the contemporary discourse. The mind plays a central role in most aspects of human life but its exact nature is disputed; some theorists suggest that all mental phenomena are private and directly knowable, transform information, have the ability to refer to and represent other entities, or are dispositions to engage in behavior.
The mind–body problem is the challenge of explaining the relation between matter and mind. The dominant position today is physicalism, which says that everything is material, meaning that minds are certain aspects or features of some material objects. The evolutionary history of the mind is tied to the development of the nervous system, which led to the formation of brains. As brains became more complex, the number and capacity of mental functions increased with particular brain areas dedicated to specific mental functions. Individual human minds also develop as they learn from experience and pass through psychological stages in the process of aging. Some people are affected by mental disorders, for which certain mental capacities do not function as they should.
It is widely accepted that animals have some form of mind, but it is controversial to which animals this applies. The topic of artificial minds poses similar challenges, with theorists discussing the possibility and consequences of creating them using computers.
The main fields of inquiry studying the mind include psychology, neuroscience, cognitive science, and philosophy. They tend to focus on different aspects of the mind and employ different methods of investigation, ranging from empirical observation and neuroimaging to conceptual analysis and thought experiments. The mind is relevant to many other fields, including epistemology, anthropology, religion, and education.
Definition
The mind is the totality of psychological phenomena and capacities, encompassing consciousness, thought, perception, sensation, feeling, mood, motivation, behavior, memory, and learning.[1] The term is sometimes used in a more narrow sense to refer only to higher or more abstract cognitive functions associated with reasoning and awareness.[2] Minds were traditionally conceived as immaterial substances or independent entities and contrasted with matter and body. In the contemporary discourse, they are more commonly seen as features of other entities and are often understood as capacities of material brains.[3] The precise definition of mind is disputed and while it is generally accepted that some non-human animals also have mind, there is no agreement on where exactly the boundary lies.[4] Despite these disputes, there is wide agreement that mind plays a central role in most aspects of human life as the seat of consciousness, emotions, thoughts, and sense of personal identity.[5] Various fields of inquiry study the mind; the main ones include psychology, cognitive science, neuroscience, and philosophy.[6]
The words psyche and mentality are usually used as synonyms of mind.[7] They are often employed in overlapping ways with the terms soul, spirit, cognition, intellect, intelligence, and brain but their meanings are not exactly the same. Some religions understand the soul as an independent entity that constitutes the immaterial essence of human beings, is of divine origin, survives bodily death, and is immortal.[8] The word spirit has various additional meanings not directly associated with mind, such as a vital principle animating living beings or a supernatural being inhabiting objects or places.[9] Cognition encompasses certain types of mental processes in which knowledge is acquired and information processed.[10] The intellect is one mental capacity responsible for thought, reasoning, and understanding[11] and is closely related to intelligence as the ability to acquire, understand, and apply knowledge.[12] The brain is the physical organ responsible for most or all mental functions.[13]
The modern English word mind originates from the Old English word gemynd, meaning "memory". This term gave rise to the Middle English words mind(e), münd(e), and mend(e), resulting in a slow expansion of meaning to cover all mental capacities. The original meaning is preserved in expressions like call to mind and keep in mind. Cognates include the Old High German gimunt, the Gothic gamunds, the ancient Greek μένος, the Latin mens, and the Sanskrit manas.[14]
Forms
The mind encompasses many functions and processes, including perception, memory, thought, imagination, motivation, emotion, attention, learning, and consciousness.[15] Perception is the process of interpreting and organizing sensory information to become acquainted with the environment. This information is acquired through sense organs receptive to various types of physical stimuli, which correspond to different forms of perception, such as vision, sound, touch, smell, and taste. The sensory information received this way is a form of raw data that is filtered and processed to actively construct a representation of the world and the objects within it. This complex process underlying perceptual experience is shaped by many factors, including the individual's past experiences, cultural background, beliefs, and expectations.[16]
Memory is the mechanism of storing and retrieving information.[17] Episodic memory handles information about specific past events in one's life and makes this information available in the present. When a person remembers what they had for dinner yesterday, they employ episodic memory. Semantic memory handles general knowledge about the world that is not tied to any specific episodes. When a person recalls that the capital of Japan is Tokyo, they usually access this general information without recalling the specific instance when they learned it. Procedural memory is memory of how to do things, such as riding a bicycle or playing a musical instrument.[18] Another distinction is between short-term memory, which holds information for brief periods, usually with the purpose of completing specific cognitive tasks, and long-term memory, which can store information indefinitely.[19]
Thinking involves the processing of information and the manipulation of mental representations. It is a goal-oriented activity that often happens in response to experiences as a symbolic process aimed at making sense of them, organizing their information, and deciding how to respond.[20] Logical reasoning is a form of thinking that starts from a set of premises and aims to arrive at a conclusion supported by these premises. This is the case when deducing that "Socrates is mortal" from the premises "Socrates is a man" and "all men are mortal".[21] Problem-solving is a closely related process that consists of several steps, such as identifying a problem, developing a plan to address it, implementing the plan, and assessing whether it worked.[22] Thinking in the form of decision-making involves considering possible courses of action to assess which one is the most beneficial.[23] As a symbolic process, thinking is deeply intertwined with language and some theorists hold that all thought happens through the medium of language.[24]
Imagination is a creative process of internally generating mental images. Unlike perception, it does not directly depend on the stimulation of sensory organs. Similar to dreaming, these images are often derived from previous experiences but can include novel combinations and elements. Imagination happens during daydreaming and plays a key role in art and literature but can also be used to come up with novel solutions to real-world problems.[25]
Motivation is an internal state that propels individuals to initiate, continue, or terminate goal-directed behavior. It is responsible for the formation of intentions to perform actions and affects what goals someone pursues, how much effort they invest in the activity, and how long they engage in it.[26] Motivation is affected by emotions, which are temporary experiences of positive or negative feelings like joy or anger. They are directed at and evaluate specific events, persons, or situations. They usually come together with certain physiological and behavioral responses.[27]
Attention is an aspect of other mental processes in which mental resources like awareness are directed towards certain features of experience and away from others. This happens when a driver focuses on the traffic while ignoring billboards on the side of the road. Attention can be controlled voluntarily in the pursuit of specific goals but can also occur involuntarily when a strong stimulus captures a person's attention.[28] Attention is relevant to learning, which is the ability of the mind to acquire new information and permanently modify its understanding and behavioral patterns. Individuals learn by undergoing experiences, which helps them adapt to the environment.[29]
Conscious and unconscious
Main articles: Consciousness and Unconscious mind
An influential distinction is between conscious and unconscious mental processes. Consciousness is the awareness of external and internal circumstances. It encompasses a wide variety of states, such as perception, thinking, fantasizing, dreaming, and altered states of consciousness.[30] In the case of phenomenal consciousness, the awareness involves a direct and qualitative experience of mental phenomena, like the auditory experience of attending a concert. Access consciousness, by contrast, refers to an awareness of information that is accessible to other mental processes but not necessarily part of current experience. For example, the information stored in a memory may be accessible when drawing conclusions or guiding actions even when the person is not explicitly thinking about it.[31]
Unconscious or nonconscious mental processes operate without the individual's awareness but can still influence mental phenomena on the level of thought, feeling, and action. Some theorists distinguish between preconscious, subconscious, and unconscious states depending on their accessibility to conscious awareness.[32] When applied to the overall state of a person rather than specific processes, the term unconscious implies that the person lacks any awareness of their environment and themselves, like during a coma.[33] The unconscious mind plays a central role in psychoanalysis as the part of the mind that contains thoughts, memories, and desires not accessible to conscious introspection. According to Sigmund Freud, the psychological mechanism of repression keeps disturbing phenomena, like unacceptable sexual and aggressive impulses, from entering consciousness to protect the individual. Psychoanalytic theory studies symptoms caused by this process and therapeutic methods to avoid them by making the repressed thoughts accessible to conscious awareness.[34]
Other categories of mental phenomena
Mental states are often divided into sensory and propositional states. Sensory states are experiences of sensory qualities, often referred to as qualia, like colors, sounds, smells, pains, itches, and hunger. Propositional states involve an attitude towards a content that can be expressed by a declarative sentence. When a person believes that it is raining, they have the propositional attitude of belief towards the content "it is raining". Different types of propositional states are characterized by different attitudes towards their content. For instance, it is also possible to hope, fear, desire, or doubt that it is raining.[35]
A mental state or process is rational if it is based on good reasons or follows the norms of rationality. For example, a belief is rational if it relies on strong supporting evidence and a decision is rational if it follows careful deliberation of all the relevant factors and outcomes. Mental states are irrational if they are not based on good reasons, such as beliefs caused by faulty reasoning, superstition, or cognitive biases, and decisions that give into temptations instead of following one's best judgment.[36] Mental states that fall outside the domain of rational evaluation are arational rather than irrational. There is controversy regarding which mental phenomena lie outside this domain; suggested examples include sensory impressions, feelings, desires, and involuntary responses.[37]
Another contrast is between dispositional and occurrent mental states. A dispositional state is a power that is not exercised. If a person believes that cats have whiskers but does not think about this fact, it is a dispositional belief. By activating the belief to consciously think about it or use it in other cognitive processes, it becomes occurrent until it is no longer actively considered or used. The great majority of a person's beliefs are dispositional most of the time.[38]
Faculties and modules
Traditionally, the mind was subdivided into mental faculties understood as capacities to perform certain functions or bring about certain processes.[39] An influential subdivision in the history of philosophy was between the faculties of intellect and will.[40] The intellect encompasses mental phenomena aimed at understanding the world and determining what to believe or what is true; the will has a practical orientation focused on desire, decision-making, action, and what is good.[41] The exact number and nature of the mental faculties are disputed and more fine-grained subdivisions have been proposed, such as dividing the intellect into the faculties of understanding and judgment or adding sensibility as an additional faculty responsible for sensory impressions.[42][a]
Diagram of the Müller-Lyer illusion
In the Müller-Lyer illusion, the horizontal black lines have the same length but the top line appears longer. The illusion persists even after becoming aware of it because of the automatic functioning of mental modules responsible for low-level visual processing.[44]
In contrast to the traditional view, more recent approaches analyze the mind in terms of mental modules rather than faculties.[45] A mental module is an inborn system of the brain that automatically performs a particular function within a specific domain without conscious awareness or effort. In contrast to faculties, the concept of mental modules is normally used to provide a more limited explanation restricted to certain low-level cognitive processes without trying to explain how they are integrated into higher-level processes such as conscious reasoning.[46][b] Many low-level cognitive processes responsible for visual perception have this automatic and unconscious nature. In the case of visual illusions like the Müller-Lyer illusion, the underlying processes continue their operation and the illusion persists even after a person has become aware of the illusion, indicating the mechanical and involuntary nature of the process.[48] Other examples of mental modules concern cognitive processes responsible for language processing and facial recognition.[49]
Theories of the nature of mind
Theories of the nature of mind aim to determine what all mental states have in common. They seek to discover the "mark of the mental", that is, the criteria that distinguish mental from non-mental phenomena.[50] Epistemic criteria say that the unique feature of mental states is how people know about them. For example, if a person has a toothache, they have direct or non-inferential knowledge that they are in pain. But they do not have this kind of knowledge of the physical causes of the pain and may have to consult external evidence through visual inspection or a visit to the dentist. Another feature commonly ascribed to mental states is that they are private, meaning that others do not have this kind of direct access to a person's mental state and have to infer it from other observations, like the pain behavior of the person with the toothache. Some philosophers claim that knowledge of some or all mental states is infallible, for instance, that a person cannot be mistaken about whether they are in pain.[51]
A related view states that all mental states are either conscious or accessible to consciousness. According to this view, when a person actively remembers the fact that the Eiffel Tower is in Paris then this state is mental because it is part of consciousness; when the person does not think about it, this belief is still a mental state because the person could bring it to consciousness by thinking about it. This view denies the existence of a "deep unconsciousness", that is, unconscious mental states that cannot in principle become conscious.[52]
Another theory says that intentionality[c] is the mark of the mental. A state is intentional if it refers to or represents something. For example, if a person perceives a piano or thinks about it then the mental state is intentional because it refers to a piano. This view distinguishes between original and derivative intentionality. Mental states have original intentionality while some non-mental phenomena have derivative intentionality. For instance, the word piano and a picture of a piano are intentional in a derivative sense: they do not directly refer to a piano but if a person looks at them, they may evoke in this person a mental state that refers to a piano. Philosophers who disagree that all mental states are intentional cite examples such as itches, tickles, and pains as possible exceptions.[54]
According to behaviorism, mental states are dispositions to engage in certain publicly observable behavior as a reaction to particular external stimuli. This view implies that mental phenomena are not private internal states but are accessible to empirical observation like regular physical phenomena.[55] Functionalism agrees that mental states do not depend on the exact internal constitution of the mind and characterizes them instead in regard to their functional role. Unlike behaviorism, this role is not limited to behavioral patterns but includes other factors as well. For example, part of the functional role of pain is given by its relation to bodily injury and its tendency to cause behavioral patterns like moaning and other mental states, like a desire to stop the pain.[56] Computationalism, a similar theory prominent in cognitive science, defines minds in terms of cognitions and computations as information processors.[57]
Theories under the umbrella of externalism emphasize the mind's dependency on the environment. According to this view, mental states and their contents are at least partially determined by external circumstances.[58] For example, some forms of content externalism hold that it can depend on external circumstances whether a belief refers to one object or another.[59] The extended mind thesis states that external circumstances not only affect the mind but are part of it, like a diary or a calculator extend the mind's capacity to store and process information.[60] The closely related view of enactivism holds that mental processes involve an interaction between organism and environment.[61]
Relation to matter
Mind–body problem
Main article: Mind–body problem
Diagram of approaches to the mind–body problem
Different approaches toward resolving the mind–body problem
The mind–body problem is the difficulty of providing a general explanation of the relationship between mind and body, for example, of the link between thoughts and brain processes. Despite their different characteristics, mind and body interact with each other, like when a bodily change causes mental discomfort or when a limb moves because of an intention.[62] According to substance dualism, minds or souls exist as distinct substances that have mental states while material things are another type of substance. This view implies that, at least in principle, minds can exist without bodies.[63] Property dualism is another form of dualism that says that mind and matter are not distinct individuals but different properties that apply to the same individual.[64] Monist views, by contrast, state that reality is made up of only one kind. According to idealists, everything is mental.[65] They understand material things as mental constructs, for example, as ideas or perceptions.[66] According to neutral monists, the world is at its most fundamental level neither physical nor mental but neutral. They see physical and mental concepts as convenient but superficial ways to describe reality.[67]
The monist view most influential in contemporary philosophy is physicalism, also referred to as materialism,[d] which states that everything is physical.[69] According to eliminative physicalism, there are no mental phenomena, meaning that things like beliefs and desires do not form part of reality.[70] Reductive physicalists defend a less radical position: they say that mental states exist but can, at least in principle, be completely described by physics without the need for special sciences like psychology. For example, behaviorists aim to analyze mental concepts in terms of observable behavior without resorting to internal mental states.[71] Type identity theory also belongs to reductive physicalism and says that mental states are the same as brain states.[72] While non-reductive physicalists agree that everything is physical, they say that mental concepts describe physical reality on a more abstract level that cannot be achieved by physics.[73] According to functionalism, mental concepts do not describe the internal constitution of physical substances but functional roles within a system.[74] One consequence of this view is that mind does not depend on brains but can also be realized by other systems that implement the corresponding functional roles, possibly also computers.[75]
The hard problem of consciousness is a central aspect of the mind–body problem: it is the challenge of explaining how physical states can give rise to conscious experience. Its main difficulty lies in the subjective and qualitative nature of consciousness, which is unlike typical physical processes. The hard problem of consciousness contrasts with the "easy problems" of explaining how certain aspects of consciousness function, such as perception, memory, or learning.[76]
Brain areas and processes
Another approach to the relation between mind and matter uses empirical observation to study how the brain works and which brain areas and processes are associated with specific mental phenomena.[77] The brain is the central organ of the nervous system and is present in all vertebrates and the majority of invertebrates. The human brain is of particular complexity and consists of 86 billion neurons, which communicate with one another via synapses.[78] They form a complex neural network and cognitive processes emerge from their electrical and chemical interactions.[79] The human brain is divided into regions that are associated with different functions. The main regions are the hindbrain, midbrain, and forebrain.[80] The hindbrain and the midbrain are responsible for many biological functions associated with basic survival while higher mental functions, ranging from thoughts to motivation, are primarily localized in the forebrain.[81]
Diagram showing the prefrontal cortex
The cerebral cortex is divided into various areas with distinct functions, like the prefrontal cortex (shown in orange) responsible for executive functions.
The primary operation of many of the main mental phenomena is located in specific areas of the forebrain. The prefrontal cortex is responsible for executive functions, such as planning, decision-making, problem-solving, and working memory. [82] The role of the sensory cortex is to process and interpret sensory information, with different subareas dedicated to different senses, like the visual and the auditory areas. A central function of the hippocampus is the formation and retrieval of long-term memories. It belongs to the limbic system, which plays a key role in the regulation of emotions through the amygdala. The motor cortex is responsible for planning, executing, and controlling voluntary movements. Broca's area is a separate region dedicated to speech production.[83] The activity of the different areas is additionally influenced by neurotransmitters, which are signaling molecules that enhance or inhibit different types of neural communication. For example, dopamine influences motivation and pleasure while serotonin affects mood and appetite.[84]
The close interrelation of brain processes and the mind is seen by the effect that physical changes of the brain have on the mind. For instance, the consumption of psychoactive drugs, like caffeine, antidepressants, alcohol, and psychedelics, temporarily affects brain chemistry with diverse effects on the mind, ranging from increased attention to mood changes, impaired cognitive functions, and hallucinations.[85] Long-term changes to the brain in the form of neurodegenerative diseases and brain injuries can lead to permanent alterations in mental functions. Alzheimer's disease in its first stage deteriorates the hippocampus, reducing the ability to form new memories and recall existing ones.[86] An often-cited case of the effects of brain injury is Phineas Gage, whose prefrontal cortex was severely damaged during a work accident when an iron rod pierced through his skull and brain. Gage survived the accident but his personality and social attitude changed significantly as he became more impulsive, irritable, and anti-social while showing little regard for social conventions and an impaired ability to plan and make rational decisions.[87] Not all these changes were permanent and Gage managed to recover and adapt in some areas.[88]
Development
Evolution
The mind has a long evolutionary history starting with the development of the nervous system and the brain.[89] While it is generally accepted today that mind is not exclusive to humans and various non-human animals have some form of mind, there is no consensus at which point exactly the mind emerged.[90] The evolution of mind is usually explained in terms of natural selection: genetic variations responsible for new or improved mental capacities, like better perception or social dispositions, have an increased chance of being passed on to future generations if they are beneficial to survival and reproduction.[91]
Minimal forms of information processing are already found in the earliest forms of life 4 to 3.5 billion years ago, like the abilities of bacteria and eukaryotic unicellular organisms to sense the environment, store this information, and react to it. Nerve cells emerged with the development of multicellular organisms more than 600 million years ago as a way to process and transmit information. About 600 to 550 million years ago, an evolutionary bifurcation happened into radially symmetric organisms[e] with ring-shaped nervous systems or a nerve net, like jellyfish, and organisms with bilaterally symmetric bodies, whose nervous systems tend to be more centralized. About 540 million years ago, the bilaterally organized organisms separated into invertebrates and vertebrates. All vertebrates, like birds and mammals, have a central nervous system including a complex brain with specialized functions while invertebrates, like clams and insects, either have no brains or tend to have simple brains.[93] With the evolution of vertebrates, their brains tended to grow and the specialization of the different brain areas tended to increase. These developments are closely related to changes in limb structures, sense organs, and living conditions with a close correspondence between the size of a brain area and the importance of its function to the organism.[94] An important step in the evolution of mammals about 200 million years ago was the development of the neocortex, which is responsible for many higher-order brain functions.[95]
The size of the brain relative to the body further increased with the development of primates, like monkeys, about 65 million years ago and later with the emergence of the first hominins about 7–5 million years ago.[96] Anatomically modern humans appeared about 300,000 to 200,000 years ago.[97] Various theories of the evolutionary processes responsible for human intelligence have been proposed. The social intelligence hypothesis says that the evolution of the human mind was triggered by the increased importance of social life and its emphasis on mental abilities associated with empathy, knowledge transfer, and meta-cognition. According to the ecological intelligence hypothesis, the main value of the increased mental capacities comes from their advantages in dealing with a complex physical environment through processes like behavioral flexibility, learning, and tool use. Other suggested mechanisms include the effects of a changed diet with energy-rich food and general benefits from an increased speed and efficiency of information processing.[98]
Individual
Besides the development of mind in general in the course of history, there is also the development of individual human minds. Some of the individual changes vary from person to person as a form of learning from experience, like forming specific memories or acquiring particular behavioral patterns. Others are more universal developments as psychological stages that all or most humans go through as they pass through early childhood, adolescence, adulthood, and old age.[99] These developments cover various areas, including intellectual, sensorimotor, linguistic, emotional, social, and moral developments.[100] Some factors affect the development of mind before birth, such as nutrition, maternal stress, and exposure to harmful substances like alcohol during pregnancy.[101]
Early childhood is marked by rapid developments as infants learn voluntary control over their bodies and interact with their environment on a basic level. Typically after about one year, this covers abilities like walking, recognizing familiar faces, and producing individual words.[102] On the emotional and social levels, they develop attachments with their primary caretakers and express emotions ranging from joy to anger, fear, and surprise.[103] An influential theory by Jean Piaget divides the cognitive development of children into four stages. The sensorimotor stage from birth until two years is concerned with sensory impressions and motor activities while learning that objects remain in existence even when not observed. In the preoperational stage until seven years, children learn to interpret and use symbols in an intuitive manner. They start employing logical reasoning to physical objects in the concrete operational stage until eleven years and extend this capacity in the following formal operational stage to abstract ideas as well as probabilities and possibilities.[104] Other important processes shaping the mind in this period are socialization and enculturation, at first through primary caretakers and later through peers and the schooling system.[105]
Psychological changes during adolescence are provoked both by physiological changes and being confronted with a different social situation and new expectations from others. An important factor in this period is change to the self-concept, which can take the form of an identity crisis. This process often involves developing individuality and independence from parents while at the same time seeking closeness and conformity with friends and peers. Further developments in this period include improvements to the reasoning ability and the formation of a principled moral viewpoint.[106]
The mind also changes during adulthood but in a less rapid and pronounced manner. Reasoning and problem-solving skills improve during early and middle adulthood. Some people experience the mid-life transition as a midlife crisis involving an inner conflict about personal identity, often associated with anxiety, a sense of lack of accomplishments in life, and an awareness of mortality. Intellectual faculties tend to decline in later adulthood, specifically the ability to learn complex unfamiliar tasks and later also the ability to remember, while people tend to become more inward-looking and cautious.[107]
Non-human
Animal
It is commonly acknowledged today that animals have some form of mind, but it is controversial to which animals this applies and how their mind differs from the human mind.[108] Different conceptions of the mind lead to different responses to this problem; when understood in a very wide sense as the capacity to process information, the mind is present in all forms of life, including insects, plants, and individual cells;[109] on the other side of the spectrum are views that deny the existence of mentality in most or all non-human animals based on the idea that they lack key mental capacities, like abstract rationality and symbolic language.[110] The status of animal minds is highly relevant to the field of ethics since it affects the treatment of animals, including the topic of animal rights.[111]
Discontinuity views state that the minds of non-human animals are fundamentally different from human minds and often point to higher mental faculties, like thinking, reasoning, and decision-making based on beliefs and desires.[112] This outlook is reflected in the traditionally influential position of defining humans as "rational animals" as opposed to all other animals.[113] Continuity views, by contrast, emphasize similarities and see the increased human mental capacities as a matter of degree rather than kind. Central considerations for this position are the shared evolutionary origin, organic similarities on the level of brain and nervous system, and observable behavior, ranging from problem-solving skills, animal communication, and reactions to and expressions of pain and pleasure. Of particular importance are the questions of consciousness and sentience, that is, to what extent non-human animals have a subjective experience of the world and are capable of suffering and feeling joy.[114]
Artificial
Main article: Philosophy of artificial intelligence
Turing test diagram
The Turing test aims to determine whether a computer can imitate human linguistic behavior to the degree that it is not possible to tell the difference between human and computer.
Some of the difficulties of assessing animal minds are also reflected in the topic of artificial minds, that is, the question of whether computer systems implementing artificial intelligence should be considered a form of mind.[115] This idea is consistent with some theories of the nature of mind, such as functionalism and its idea that mental concepts describe functional roles, which are implemented by biological brains but could in principle also be implemented by artificial devices.[116] The Turing test is a traditionally influential procedure to test artificial intelligence: a person exchanges messages with two parties, one of them a human and the other a computer. The computer passes the test if it is not possible to reliably tell which party is the human and which one is the computer. While there are computer programs today that may pass the Turing test, this alone is usually not accepted as conclusive proof of mindedness.[117] For other aspects of mind, it is more controversial whether computers can, in principle, implement them, such as desires, feelings, consciousness, and free will.[118]
This problem is often discussed through the contrast between weak and strong artificial intelligence. Weak or narrow artificial intelligence is limited to specific mental capacities or functions. It focuses on a particular task or a narrow set of tasks, like autonomous driving, speech recognition, or theorem proving. The goal of strong AI, also termed artificial general intelligence, is to create a complete artificial person that has all the mental capacities of humans, including consciousness, emotion, and reason.[119] It is controversial whether strong AI is possible; influential arguments against it include John Searle's Chinese Room Argument and Hubert Dreyfus's critique based on Heideggerian philosophy.[120]
Mental health and disorder
Main articles: Mental health, Mental disorder, and Psychopathology
Mental health is a state of mind characterized by internal equilibrium and well-being in which mental capacities function as they should. Some theorists emphasize positive features such as the abilities of a person to realize their potential, express and modulate emotions, cope with adverse life situations, and fulfill their social role. Negative definitions, by contrast, see mental health as the absence of mental illness in the form of mental disorders.[121] Mental disorders are abnormal patterns of thought, emotion, or behavior that deviate not only from how a mental capacity works on average but from the norm of how it should work while usually causing some form of distress. The content of those norms is controversial and there are differences from culture to culture; for example, homosexuality was historically considered a mental disorder by medical professionals, a view which only changed in the late 20th century.[122]
Photo of hand washing
Obsessive–compulsive disorder is a mental disorder in which a person follows compulsive rituals, like excessive hand washing, to alleviate anxiety caused by intrusive thoughts.
There is a great variety of mental disorders, each associated with a different form of malfunctioning. Anxiety disorders involve intense and persistent fear that is disproportionate to the actual threat and significantly impairs everyday life, like social phobias, which involve irrational fear of certain social situations. Anxiety disorders also include obsessive–compulsive disorder, for which the anxiety manifests in the form of intrusive thoughts that the person tries to alleviate by following compulsive rituals.[123] Mood disorders cause intensive moods or mood swings that are inconsistent with the external circumstances and can last for extensive periods. For instance, people affected by bipolar disorder experience extreme mood swings between manic states of euphoria and depressive states of hopelessness.[124] Personality disorders are characterized by enduring patterns of maladaptive behavior that significantly impair regular life, like paranoid personality disorder, which leads people to be deeply suspicious of the motives of others without rational basis.[125] Psychotic disorders are among the most severe mental illnesses and involve a distorted relation to reality in the form of hallucinations and delusions, as seen in schizophrenia.[126] Other disorders include dissociative disorders and eating disorders.[127]
There are different approaches to treating mental disorders and the most appropriate treatment usually depends on factors like the type of disorder, its cause, and the person's general condition. Psychotherapeutic methods use personal interaction with a therapist to understand the disorder and help the patient change their patterns of thinking, feeling, and acting.[128] Psychoanalysis conceives the source of mental disorders as a conflict between the conscious and the unconscious mind. The therapeutic aim is to gain insight into unconscious conflicts to resolve them.[129] Cognitive behavioral therapy also focuses on insight but gives more emphasis to conscious mental phenomena to identify and change irrational beliefs and negative thought patterns.[130] Behavior therapy is a related approach that relies on classical conditioning to unlearn harmful behaviors rather than alter thought patterns.[131] Humanistic therapies try to help people gain insight into their self-worth and empower them to resolve their problems and discover their potential.[132] Drug therapies use medication to alter the brain chemistry involved in the disorder through substances like antidepressants, antipsychotics, mood stabilizers, and anxiolytics. They fall into the domain of psychiatry and are sometimes used in combination with psychotherapeutic methods.[133]
Fields and methods of inquiry
Various fields of inquiry study the mind, including psychology, neuroscience, philosophy, and cognitive science. They differ from each other in the aspects of mind they investigate and the methods they employ in the process.[134] The study of the mind poses various problems since it is difficult to directly examine, manipulate, and measure it. Trying to circumvent this problem by investigating the brain comes with new challenges of its own, mainly because of the brain's complexity as a neural network consisting of billions of neurons, each with up to 10,000 links to other neurons.[135]
Psychology
Main article: Psychology
Psychology is the scientific study of mind and behavior. It investigates conscious and unconscious mental phenomena, including perception, memory, feeling, thought, decision, intelligence, and personality. It is further interested in their outward manifestation in the form of observable behavioral patterns and how these patterns depend on external circumstances and are shaped by learning.[136] Psychology is a wide discipline that includes many subfields. Cognitive psychology is interested in higher-order mental activities like thinking, problem-solving, reasoning, and concept formation.[137] Biological psychology seeks to understand the underlying mechanisms on the physiological level and how they depend on genetic transmission and the environment.[138] Developmental psychology studies the development of the mind from childhood to old age while social psychology examines the influence of social contexts on mind and behavior.[139] Further subfields include comparative, clinical, educational, occupational, and neuropsychology.[140]
Psychologists use a great variety of methods to study the mind. Experimental approaches set up a controlled situation, either in the laboratory or the field, in which they modify independent variables and measure their effects on dependent variables. This approach makes it possible to identify causal relations between the variables. For example, to determine whether people with similar interests (independent variable) are more likely to become friends (dependent variables), participants of a study could be paired with either similar or dissimilar participants. After giving the pairs time to interact, it is assessed whether the members of similar pairs have more positive attitudes toward one another than the members of dissimilar pairs.[141]
Correlational methods examine the strength of association between two variables without establishing a causal relationship between them.[142] The survey method presents participants with a list of questions aimed at eliciting information about their mental attitudes, behavior, and other relevant factors. It analyzes how participants respond to questions and how answers to different questions correlate with one another.[143] Surveys usually have a large number of participants in contrast to case studies, which focus on an in-depth examination of a single subject or a small group of subjects, often to examine rare phenomena or explore new fields.[144] Further methods include longitudinal studies, naturalistic observation, and phenomenological description of experience.[145]
Neuroscience
Main article: Neuroscience
fMRI image
Functional magnetic resonance imaging is a neuroimaging technique to detect brain areas with increased neural activity (shown in orange).
Neuroscience is the study of the nervous system. Its primary focus is the central nervous system and the brain in particular, but it also investigates the peripheral nervous system mainly responsible for connecting the central nervous system to the limbs and organs. Neuroscience examines the implementation of mental phenomena on a physiological basis. It covers various levels of analysis; on the small scale, it studies the molecular and cellular basis of the mind, dealing with the constitution of and interaction between individual neurons; on the large scale, it analyzes the architecture of the brain as a whole and its division into regions with different functions.[146]
Neuroimaging techniques are of particular importance as the main research methods of neuroscientists. Functional magnetic resonance imaging (fMRI) measures changes in the magnetic field of the brain associated with blood flow. Areas of increased blood flow indicate that the corresponding brain region is particularly active. Positron emission tomography (PET) uses radioactive substances to detect a range of metabolic changes in the brain. Electroencephalography (EEG) measures the electrical activity of the brain, usually by placing electrodes on the scalp and measuring the voltage differences between them. These techniques are often employed to measure brain changes under particular circumstances, for example, while engaged in a specific cognitive task. Important insights are also gained from patients and laboratory animals with brain damage in particular areas to assess the function of the damaged area and how its absence affects the remaining brain.[147]
Philosophy
Main article: Philosophy of mind
Philosophy of mind examines the nature of mental phenomena and their relation to the physical world. It seeks to understand the "mark of the mental", that is, the features that all mental states have in common. It further investigates the essence of different types of mental phenomena, such as beliefs, desires, emotions, intentionality, and consciousness while exploring how they are related to one another. Philosophy of mind also examines solutions to the mind–body problem, like dualism, idealism, and physicalism, and assesses arguments for and against them. Further topics are personal identity and free will.[148]
Diagram of the brain-in-a-vat thought experiment
Philosophers use thought experiments to explore the nature of the mind and its relation to matter, for example, by imagining how a brain in a vat would experience reality if a supercomputer fed it the same electrical stimulation a normal brain receives.
While philosophers of mind also include empirical considerations in their inquiry, they differ from fields like psychology and neuroscience by giving significantly more emphasis to non-empirical forms of inquiry. One such method is conceptual analysis, which aims to clarify the meaning of concepts, like mind and intention, by decomposing them to identify their semantic parts.[149] Thought experiments are often used to evoke intuitions about abstract theories to assess their coherence and plausibility: philosophers imagine a situation relevant to a theory and employ counterfactual thinking to assess the possible consequences of this theory, as in Mary the color scientist, philosophical zombies, and brain in a vat-scenarios.[150] Because of the subjective nature of the mind, the phenomenological method is also commonly used to analyze the structure of consciousness by describing experience from the first-person perspective.[151]
Cognitive science
Main article: Cognitive science
Cognitive science is the interdisciplinary study of mental processes. It aims to overcome the challenge of understanding something as complex as the mind by integrating research from diverse fields ranging from psychology and neuroscience to philosophy, linguistics, and artificial intelligence. Unlike these disciplines, it is not a unified field but a collaborative effort. One difficulty in synthesizing their insights is that each of these disciplines explores the mind from a different perspective and level of abstraction while using different research methods to arrive at its conclusion.[152]
Cognitive science aims to overcome this difficulty by relying on a unified conceptualization of minds as information processors. This means that mental processes are understood as computations that retrieve, transform, store, and transmit information.[152] For example, perception retrieves sensory information from the environment and transforms it to extract meaningful patterns that can be used in other mental processes, such as planning and decision-making.[153] Cognitive science relies on different levels of description to analyze cognitive processes; the most abstract level focuses on the basic problem the process is supposed to solve and the reasons why the organism needs to solve it; the intermediate level seeks to uncover the algorithm as a formal step-by-step procedure to solve the problem; the most concrete level asks how the algorithm is implemented through physiological changes on the level of the brain.[154] Another methodology to deal with the complexity of the mind is to analyze the mind as a complex system composed of individual subsystems that can be studied independently of one another.[155]
Relation to other fields
The mind is relevant to many fields. In epistemology, the problem of other minds is the challenge of explaining how it is possible to know that people other than oneself have a mind. The difficulty arises from the fact that people directly experience their own minds but do not have the same access to the minds of others. According to a common view, it is necessary to rely on perception to observe the behavior of others and then infer that they have a mind based on analogical or abductive reasoning.[156] Closely related to this problem is theory of mind in psychology, which is the ability to understand that other people possess beliefs, desires, intentions, and feelings that may differ from one's own.[157]
Anthropology is interested in how different cultures conceptualize the nature of mind and its relation to the world. These conceptualizations affect the way people understand themselves, experience illness, and interpret ritualistic practices as attempts to commune with spirits. Some cultures do not draw a strict boundary between mind and world by allowing that thoughts can pass directly into the world and manifest as beneficial or harmful forces. Others strictly separate the mind as an internal phenomenon without supernatural powers from external reality.[158] Sociology is a related field concerned with the connections between mind, society, and behavior.[159]
The concept of mind plays a central role in various religions. Buddhists say that there is no enduring self underlying mental activity and analyze the mind as a stream of constantly changing experiences characterized by five aspects or "aggregates": material form, feelings, perception, volition, and consciousness.[160] Hindus, by contrast, affirm the existence of a permanent self. In an influential analogy, the human mind is compared to a horse-drawn chariot: the horses are the senses, which lure the sense mind corresponding to the reins through sensual pleasures but are controlled by the charioteer embodying the intellect while the self is a passenger.[161] In traditional Christian philosophy, mind and soul are closely intertwined as the immaterial aspect of humans that may survive bodily death.[162] Islamic thought distinguishes between the mind, spirit, heart, and self as interconnected aspects of the spiritual dimension of humans.[163] Daoism and Confucianism use the concept of heart-mind as the center of cognitive and emotional life, encompassing thought, understanding, will, desire, and mood.[164]
In the field of education, the minds of students are shaped through the transmission of knowledge, skills, and character traits as a process of socialization and enculturation. This is achieved through different teaching methods including the contrast between group work and individual learning and the use of instructional media.[165] Teacher-centered education positions the teacher as the central authority controlling the learning process whereas in student-centered education, students have a more active role in shaping classroom activities.[166] The choice of the most effective method to develop the minds of the learners is determined by various factors, including the topic and the learner's age and skill level.[167]
Phrenological diagram of brain functions
Phrenology was a pseudoscientific attempt to correlate mental functions to brain areas.
The mind is a frequent subject of pseudoscientific inquiry. Phrenology was an early attempt to correlate mental functions with specific brain areas. While its central claims about predicting mental traits by measuring bumps on the skull did not survive scientific scrutiny, the underlying idea that certain mental functions are localized in particular regions of the brain is now widely accepted.[168] Parapsychologists seek to discover and study paranormal mental abilities ranging from clairvoyance to telepathy and telekinesis.[169]
See also
Conscience
Embodied cognition
Explanatory gap
Ideasthesia
Mental energy
Mind at Large
Neural Darwinism
Outline of human intelligence
Outline of thought
Subjective character of experience
References
Notes
Mental faculties also play a central role in the Indian tradition, such as the contrast between the sense mind (manas) and intellect (buddhi).[43]
A different perspective is proposed by the massive modularity hypothesis, which states that the mind is entirely composed of modules with high-level modules establishing the connection between low-level modules.[47]
Intentionality is to be distinguished from intention in the sense of having a plan to perform a certain action.[53]
The two terms are usually treated as synonyms but some theorists distinguish them by holding that materialism is restricted to matter while physicalism is a wider term that includes additional physical phenomena, like forces.[68]
They include cnidarians and ctenophorans.[92]
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Rescorla 2023, Lead Section
Aydede 2017
Singer 2000, pp. 227–228
Kind 2017, Lead Section
American Psychological Association 2018
Hoff 2020, pp. 617–618
Weiner 2000, pp. 314–315
Helms 2000, lead section
Bernstein & Nash 2006, pp. 298, 336–337
Müller 1996, p. 14
Bernstein & Nash 2006, pp. 322–323, 337
American Psychological Association 2018a
Bernstein & Nash 2006, pp. 126–127, 131
American Psychological Association 2018b
McPeek 2009, Attention: Physiological
Bernstein & Nash 2006, pp. 171, 202
American Psychological Association 2018c
Bernstein & Nash 2006, pp. 137–138
Davies 2001, pp. 190–192
Gennaro, Lead Section, § 1. Terminological Matters: Various Concepts of Consciousness
Davies 2001, pp. 191–192
Smithies 2019, pp. 83–84
Gennaro, § 1. Terminological Matters: Various Concepts of Consciousness
Bernstein & Nash 2006, pp. 137–138
Kihlstrom & Tobias 1991, p. 212
American Psychological Association 2018d
Gennaro, Lead Section, § 1. Terminological Matters: Various Concepts of Consciousness
Kind 2023, § 2.1 Phenomenal Consciousness
Mijoia 2005, pp. 1818–1819
Bernstein & Nash 2006, pp. 137–138
Steinberg Gould 2020, p. 151
American Psychological Association 2018d
Carel 2006, p. 176
Kim 2005, pp. 607–608
Swinburne 2013, pp. 72–73
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Harman 2013, pp. 1–2
Broome 2021, § 1. Normativity and Reasons, §2. The Meaning of "Rationality"
Siegel 2017, p. 157
Maruyama 2020, pp. 172–173
Nolfi 2015, pp. 41–42
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Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as well as the inanimate physical environment. It is the computed response of the system or organism to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or covert, and voluntary or involuntary.[1]
Taking a behavior informatics perspective, a behavior consists of actor, operation, interactions, and their properties. This can be represented as a behavior vector.[2]
Models
Biology
Main article: Behavioral ecology
Although disagreement exists as to how to precisely define behavior in a biological context, one common interpretation based on a meta-analysis of scientific literature states that "behavior is the internally coordinated responses (actions or inactions) of whole living organisms (individuals or groups) to internal or external stimuli".[3]
A broader definition of behavior, applicable to plants and other organisms, is similar to the concept of phenotypic plasticity. It describes behavior as a response to an event or environment change during the course of the lifetime of an individual, differing from other physiological or biochemical changes that occur more rapidly, and excluding changes that are a result of development (ontogeny).[4][5]
Behaviors can be either innate or learned from the environment.
Behaviour can be regarded as any action of an organism that changes its relationship to its environment. Behavior provides outputs from the organism to the environment.[6]
Human behavior
Main article: Human behavior
The endocrine system and the nervous system likely influence human behavior. Complexity in the behavior of an organism may be correlated to the complexity of its nervous system. Generally, organisms with more complex nervous systems have a greater capacity to learn new responses and thus adjust their behavior.[7]
Animal behavior
Main article: Ethology
Ethology is the scientific and objective study of animal behavior, usually with a focus on behavior under natural conditions, and viewing behavior as an evolutionarily adaptive trait.[8] Behaviorism is a term that also describes the scientific and objective study of animal behavior, usually referring to measured responses to stimuli or trained behavioral responses in a laboratory context, without a particular emphasis on evolutionary adaptivity.[9]
Consumer behavior
Consumers behavior
Consumer behavior involves the processes consumers go through, and reactions they have towards products or services.[10] It has to do with consumption, and the processes consumers go through around purchasing and consuming goods and services.[11] Consumers recognise needs or wants, and go through a process to satisfy these needs. Consumer behavior is the process they go through as customers, which includes types of products purchased, amount spent, frequency of purchases and what influences them to make the purchase decision or not.
Circumstances that influence consumer behaviour are varied, with contributions from both internal and external factors.[11] Internal factors include attitudes, needs, motives, preferences and perceptual processes, whilst external factors include marketing activities, social and economic factors, and cultural aspects.[11] Doctor Lars Perner of the University of Southern California claims that there are also physical factors that influence consumer behavior, for example, if a consumer is hungry, then this physical feeling of hunger will influence them so that they go and purchase a sandwich to satisfy the hunger.[12]
Consumer decision making
Lars Perner presents a model that outlines the decision-making process involved in consumer behaviour. The process initiates with the identification of a problem, wherein the consumer acknowledges an unsatisfied need or desire. Subsequently, the consumer proceeds to seek information, whereas for low-involvement products, the search tends to rely on internal resources, retrieving alternatives from memory. Conversely, for high-involvement products, the search is typically more extensive, involving activities like reviewing reports, reading reviews, or seeking recommendations from friends.
The consumer will then evaluate his or her alternatives, comparing price, and quality, doing trade-offs between products, and narrowing down the choice by eliminating the less appealing products until there is one left. After this has been identified, the consumer will purchase the product.
Finally, the consumer will evaluate the purchase decision, and the purchased product, bringing in factors such as value for money, quality of goods, and purchase experience.[12] However, this logical process does not always happen this way, people are emotional and irrational creatures. People make decisions with emotion and then justify them with logic according to Robert Cialdini Ph.D. Psychology.[13]
How the 4P's influence consumer behavior
The Marketing mix (4 P's) are a marketing tool and stand for Price, Promotion, Product, and Placement.
Due to the significant impact of business-to-consumer marketing on consumer behavior, the four elements of the marketing mix, known as the 4 P's (product, price, place, and promotion), exert a notable influence on consumer behavior. The price of a good or service is largely determined by the market, as businesses will set their prices to be similar to that of other businesses so as to remain competitive whilst making a profit. When market prices for a product are high, it will cause consumers to purchase less and use purchased goods for longer periods of time, meaning they are purchasing the product less often. Alternatively, when market prices for a product are low, consumers are more likely to purchase more of the product, and more often.
The way that promotion influences consumer behavior has changed over time. In the past, large promotional campaigns and heavy advertising would convert into sales for a business, but nowadays businesses can have success on products with little or no advertising. This is due to the Internet and in particular social media. They rely on word of mouth from consumers using social media, and as products trend online, so sales increase as products effectively promote themselves. Thus, promotion by businesses does not necessarily result in consumer behavior trending towards purchasing products.
The way that product influences consumer behavior is through consumer willingness to pay, and consumer preferences. This means that even if a company were to have a long history of products in the market, consumers will still pick a cheaper product over the company in question's product if it means they will pay less for something that is very similar. This is due to consumer willingness to pay, or their willingness to part with the money they have earned. The product also influences consumer behavior through customer preferences. For example, take Pepsi vs Coca-Cola, a Pepsi-drinker is less likely to purchase Coca-Cola, even if it is cheaper and more convenient. This is due to the preference of the consumer, and no matter how hard the opposing company tries they will not be able to force the customer to change their mind.
Product placement in the modern era has little influence on consumer behavior, due to the availability of goods online. If a customer can purchase a good from the comfort of their home instead of purchasing in-store, then the placement of products is not going to influence their purchase decision.[14]
In management
Behavior outside of psychology includes
Organizational
In management, behaviors are associated with desired or undesired focuses. Managers generally note what the desired outcome is, but behavioral patterns can take over. These patterns are the reference to how often the desired behavior actually occurs. Before a behavior actually occurs, antecedents focus on the stimuli that influence the behavior that is about to happen. After the behavior occurs, consequences fall into place. Consequences consist of rewards or punishments.
Social behavior
Main article: Social behavior
Social behavior is behavior among two or more organisms within the same species, and encompasses any behavior in which one member affects the other. This is due to an interaction among those members. Social behavior can be seen as similar to an exchange of goods, with the expectation that when one gives, one will receive the same. This behavior can be affected by both the qualities of the individual and the environmental (situational) factors. Therefore, social behavior arises as a result of an interaction between the two—the organism and its environment. This means that, in regards to humans, social behavior can be determined by both the individual characteristics of the person, and the situation they are in.
Behavior informatics
Behavior informatics[2] also called behavior computing,[15] explores behavior intelligence and behavior insights from the informatics and computing perspectives.
Different from applied behavior analysis from the psychological perspective, BI builds computational theories, systems and tools to qualitatively and quantitatively model, represent, analyze, and manage behaviors of individuals, groups and/or organizations.
Health
See also: Health belief model, Theory of planned behavior, Transtheoretical model, and Self-efficacy
Health behavior refers to a person's beliefs and actions regarding their health and well-being. Health behaviors are direct factors in maintaining a healthy lifestyle. Health behaviors are influenced by the social, cultural, and physical environments in which we live. They are shaped by individual choices and external constraints. Positive behaviors help promote health and prevent disease, while the opposite is true for risk behaviors.[16] Health behaviors are early indicators of population health. Because of the time lag that often occurs between certain behaviors and the development of disease, these indicators may foreshadow the future burdens and benefits of health-risk and health-promoting behaviors.
Correlates
A variety of studies have examined the relationship between health behaviors and health outcomes (e.g., Blaxter 1990) and have demonstrated their role in both morbidity and mortality.
These studies have identified seven features of lifestyle which were associated with lower morbidity and higher subsequent long-term survival (Belloc and Breslow 1972):
Avoiding snacks
Eating breakfast regularly
Exercising regularly
Maintaining a desirable body weight
Moderate alcohol intake
Not smoking
Sleeping 7–8hrs per night
Health behaviors impact upon individuals' quality of life, by delaying the onset of chronic disease and extending active lifespan. Smoking, alcohol consumption, diet, gaps in primary care services and low screening uptake are all significant determinants of poor health, and changing such behaviors should lead to improved health. For example, in US, Healthy People 2000, United States Department of Health and Human Services, lists increased physical activity, changes in nutrition and reductions in tobacco, alcohol and drug use as important for health promotion and disease prevention.
Treatment approach
Any interventions done are matched with the needs of each individual in an ethical and respected manner. Health belief model encourages increasing individuals' perceived susceptibility to negative health outcomes and making individuals aware of the severity of such negative health behavior outcomes. E.g. through health promotion messages. In addition, the health belief model suggests the need to focus on the benefits of health behaviors and the fact that barriers to action are easily overcome. The theory of planned behavior suggests using persuasive messages for tackling behavioral beliefs to increase the readiness to perform a behavior, called intentions. The theory of planned behavior advocates the need to tackle normative beliefs and control beliefs in any attempt to change behavior. Challenging the normative beliefs is not enough but to follow through the intention with self-efficacy from individual's mastery in problem solving and task completion is important to bring about a positive change.[17] Self efficacy is often cemented through standard persuasive techniques.
See also
icon Medicine portal
Psychology portal
icon Sex portal
icon Society portal
Applied behavior analysis
Behavioral cusp
Behavioral economics
Behavioral genetics
Behavioral sciences
Cognitive bias
Evolutionary physiology
Experimental analysis of behavior
Human sexual behavior
Herd behavior
Instinct
Mere-measurement effect
Motivation
Normality (behavior)
Organizational studies
Radical behaviorism
Reasoning
Rebellion
Social relation
Theories of political behavior
Work behavior
References
Elizabeth A. Minton, Lynn R. Khale (2014). Belief Systems, Religion, and Behavioral Economics. New York: Business Expert Press LLC. ISBN 978-1-60649-704-3.
Cao, Longbing (2010). "In-depth Behavior Understanding and Use: the Behavior Informatics Approach". Information Science. 180 (17): 3067–3085. arXiv:2007.15516. doi:10.1016/j.ins.2010.03.025. S2CID 7400761.
Levitis, Daniel; William Z. Lidicker, Jr; Glenn Freund (June 2009). "Behavioural biologists do not agree on what constitutes behaviour" (PDF). Animal Behaviour. 78 (1): 103–10. doi:10.1016/j.anbehav.2009.03.018. PMC 2760923. PMID 20160973. Archived (PDF) from the original on 9 October 2022.
Karban, R. (2008). Plant behaviour and communication. Ecology Letters 11 (7): 727–739, [1] Archived 4 October 2015 at the Wayback Machine.
Karban, R. (2015). Plant Behavior and Communication. In: Plant Sensing and Communication. Chicago and London: The University of Chicago Press, pp. 1-8, [2].
Dusenbery, David B. (2009). Living at Micro Scale, p. 124. Harvard University Press, Cambridge, Massachusetts ISBN 978-0-674-03116-6.
Gregory, Alan (2015). Book of Alan: A Universal Order. Xlibris Corporation. ISBN 978-1-5144-2053-9.
"Definition of ethology". Merriam-Webster. Retrieved 9 September 2016.
"Definition of behaviorism". Merriam-Webster. Retrieved 9 September 2016.
"Behaviourism". Oxford Dictionaries. Archived from the original on 12 July 2012. Retrieved 9 September 2016.
"The Regents of the University of California".
Szwacka-Mokrzycka, Joanna (2015). "Trends in Consumer Behavior Changes. Overview of Concepts". Acta Scientiarum Polonorum. Oeconomia. Retrieved 30 March 2016.[permanent dead link]
Perner, Lars (2008). "Consumer Behaviour". Consumer Psychologist. Retrieved 30 March 2016.
Schaller, Mark; Neuberg, Steven L. (1 March 2012), Kenrick, Douglas T. (ed.), "Six Degrees of Bob Cialdini and Five Principles of Scientific Influence", Six Degrees of Social Influence, Oxford University Press, pp. 3–13, doi:10.1093/acprof:osobl/9780199743056.003.0001, ISBN 978-0-19-974305-6, retrieved 26 June 2023
Clemons, Eric (2008). "How Information Changes Consumer Behavior and How Consumer Behavior Determines Corporate Strategy". Journal of Management Information Systems. 25 (2): 13–40. doi:10.2753/MIS0742-1222250202. S2CID 16370526.[permanent dead link]
Cao, L.; Yu, P., eds. (2012). Behavior Computing: Modeling, Analysis, Mining and Decision. Springer. ISBN 978-1-4471-2969-1.
"Health behaviours". statcan.gc.ca. 11 January 2010. Retrieved 15 January 2016.
Gollwitzer, Peter M. (1993). "Goal Achievement: The Role of Intentions" (PDF). European Review of Social Psychology. 4 (1): 141–185. doi:10.1080/14792779343000059.
General
Cao, L. (2014). Behavior Informatics: A New Perspective. IEEE Intelligent Systems (Trends and Controversies), 29(4): 62–80.
Clemons, E. K. (2008). "How Information Changes Consumer Behavior and How Consumer Behavior Determines Corporate Strategy". Journal of Management Information Systems. 25 (2): 13–40. doi:10.2753/mis0742-1222250202. S2CID 16370526.
Dowhan, D (2013). "Hitting Your Target". Marketing Insights. 35 (2): 32–38.
Perner, L. (2008), Consumer behavior. University of Southern California, Marshall School of Business. Retrieved from http://www.consumerpsychologist.com/intro_Consumer_Behavior.html
Szwacka-Mokrzycka, J (2015). "TRENDS IN CONSUMER behavior CHANGES. OVERVIEW OF CONCEPTS". Acta Scientiarum Polonorum. Oeconomia. 14 (3): 149–156.
Further reading
Bateson, P. (2017) behavior, Development and Evolution. Open Book Publishers, Cambridge. ISBN 978-1-78374-250-9.
Plomin, Robert; DeFries, John C.; Knopik, Valerie S.; Neiderhiser, Jenae M. (24 September 2012). Behavioral Genetics. Shaun Purcell (Appendix: Statistical Methods in Behavioral Genetics). Worth Publishers. ISBN 978-1-4292-4215-8. Retrieved 4 September 2013.
Flint, Jonathan; Greenspan, Ralph J.; Kendler, Kenneth S. (28 January 2010). How Genes Influence Behavior. Oxford University Press. ISBN 978-0-19-955990-9.
External links
Wikimedia Commons has media related to Behavior.
Look up behavior in Wiktionary, the free dictionary.
What is behavior? Baby don't ask me, don't ask me, no more at Earthling Nature.
behaviorinformatics.org
Links to review articles by Eric Turkheimer and co-authors on behavior research
Links to IJCAI2013 tutorial on behavior informatics and computing
Authority control databases Edit this at Wikidata
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Consciousness, at its simplest, is awareness of internal and external existence.[1] However, its nature has led to millennia of analyses, explanations and debate by philosophers, theologians, and scientists. Opinions differ about what exactly needs to be studied or even considered consciousness. In some explanations, it is synonymous with the mind, and at other times, an aspect of mind. In the past, it was one's "inner life", the world of introspection, of private thought, imagination and volition.[2] Today, it often includes any kind of cognition, experience, feeling or perception. It may be awareness, awareness of awareness, or self-awareness either continuously changing or not.[3][4] The disparate range of research, notions and speculations raises a curiosity about whether the right questions are being asked.[5]
Examples of the range of descriptions, definitions or explanations are: ordered distinction between self and environment, simple wakefulness, one's sense of selfhood or soul explored by "looking within"; being a metaphorical "stream" of contents, or being a mental state, mental event, or mental process of the brain.
Etymology
The words "conscious" and "consciousness" in English date to the 1600s and the first recorded use of "conscious" as a simple adjective was applied figuratively to inanimate objects ("the conscious Groves", 1643).[6]: 175 It derived from the Latin conscius (con- "together" and scio "to know") which meant "knowing with" or "having joint or common knowledge with another", especially as in sharing a secret.[7] Thomas Hobbes in Leviathan (1651) wrote: "Where two, or more men, know of one and the same fact, they are said to be Conscious of it one to another."[8] There were also many occurrences in Latin writings of the phrase conscius sibi, which translates literally as "knowing with oneself", or in other words "sharing knowledge with oneself about something". This phrase has the figurative sense of "knowing that one knows", which is something like the modern English word "conscious", but it was rendered into English as "conscious to oneself" or "conscious unto oneself". For example, Archbishop Ussher wrote in 1613 of "being so conscious unto myself of my great weakness".[9]
The Latin conscientia, literally 'knowledge-with', first appears in Roman juridical texts by writers such as Cicero. It means a kind of shared knowledge with moral value, specifically what a witness knows of someone else's deeds.[10][11] Although René Descartes (1596–1650), writing in Latin, is generally taken to be the first philosopher to use conscientia in a way less like the traditional meaning and more like the way modern English speakers would use "conscience", his meaning is nowhere defined.[12] In Search after Truth (Regulæ ad directionem ingenii ut et inquisitio veritatis per lumen naturale, Amsterdam 1701) he wrote the word with a gloss: conscientiâ, vel interno testimonio (translatable as "conscience, or internal testimony").[13][14] It might mean the knowledge of the value of one’s own thoughts.[12]
John Locke, a 17th-century British Age of Enlightenment philosopher
The origin of the modern concept of consciousness is often attributed to John Locke who defined the word in his Essay Concerning Human Understanding, published in 1690, as "the perception of what passes in a man's own mind".[15][16] The essay strongly influenced 18th-century British philosophy, and Locke's definition appeared in Samuel Johnson's celebrated Dictionary (1755).[17]
The French term conscience is defined roughly like English "consciousness" in the 1753 volume of Diderot and d'Alembert's Encyclopédie as "the opinion or internal feeling that we ourselves have from what we do".[18]
The problem of definition
About forty meanings attributed to the term consciousness can be identified and categorized based on functions and experiences. The prospects for reaching any single, agreed-upon, theory-independent definition of consciousness appear remote.[19]
Scholars are divided as to whether Aristotle had a concept of consciousness. He does not use any single word or terminology that is clearly similar to the phenomenon or concept defined by John Locke. Victor Caston contends that Aristotle did have a concept more clearly similar to perceptual awareness.[20]
The modern dictionary definitions of the word consciousness evolved through several centuries and reflect a range of seemingly related meanings, with some differences that have been controversial, such as the distinction between 'inward awareness' and 'perception' of the physical world, or the distinction between 'conscious' and 'unconscious', or the notion of a "mental entity" or "mental activity" that is not physical.
The common usage definitions of consciousness in Webster's Third New International Dictionary (1966 edition, Volume 1, page 482) are as follows:
awareness or perception of an inward psychological or spiritual fact; intuitively perceived knowledge of something in one's inner self
inward awareness of an external object, state, or fact
concerned awareness; INTEREST, CONCERN—often used with an attributive noun [e.g. class consciousness]
the state or activity that is characterized by sensation, emotion, volition, or thought; mind in the broadest possible sense; something in nature that is distinguished from the physical
the totality in psychology of sensations, perceptions, ideas, attitudes, and feelings of which an individual or a group is aware at any given time or within a particular time span—compare STREAM OF CONSCIOUSNESS
waking life (as that to which one returns after sleep, trance, fever) wherein all one's mental powers have returned . . .
the part of mental life or psychic content in psychoanalysis that is immediately available to the ego—compare PRECONSCIOUS, UNCONSCIOUS
The Cambridge Dictionary defines consciousness as "the state of understanding and realizing something."[21] The Oxford Living Dictionary defines consciousness as "The state of being aware of and responsive to one's surroundings.", "A person's awareness or perception of something." and "The fact of awareness by the mind of itself and the world."[22]
Philosophers have attempted to clarify technical distinctions by using a jargon of their own. The Routledge Encyclopedia of Philosophy in 1998 defines consciousness as follows:
Consciousness—Philosophers have used the term 'consciousness' for four main topics: knowledge in general, intentionality, introspection (and the knowledge it specifically generates) and phenomenal experience... Something within one's mind is 'introspectively conscious' just in case one introspects it (or is poised to do so). Introspection is often thought to deliver one's primary knowledge of one's mental life. An experience or other mental entity is 'phenomenally conscious' just in case there is 'something it is like' for one to have it. The clearest examples are: perceptual experience, such as tastings and seeings; bodily-sensational experiences, such as those of pains, tickles and itches; imaginative experiences, such as those of one's own actions or perceptions; and streams of thought, as in the experience of thinking 'in words' or 'in images'. Introspection and phenomenality seem independent, or dissociable, although this is controversial.[23]
Traditional metaphors for 'mind'
During the early 1800's, geology was discovering buried layers of history in the earth's crust, inspiring a popular metaphor that the mind also had hidden "layers which recorded the past of the individual".[24]: 3 By 1875 most psychologists believed that "consciousness was but a small part of mental life",[24]: 3 and this idea underlay the goal of Freudian therapy, to expose the unconscious layer of the mind.
Other metaphors from various sciences inspired other analyses of the mind, for example: J. F. Herbart described 'ideas' as being 'attracted' and 'repulsed' like magnets; J. S. Mill developed the idea of "mental chemistry" and "mental compounds", and Edward B. Titchener sought the 'structure' of the mind by analyzing its "elements". The abstract idea of 'states of consciousness' mirrored physicists' concept of states of matter.
In 1892 William James noted that the "ambiguous word 'content' has been recently invented instead of 'object'" and that the metaphor of mind as a container seemed to minimize the dualistic problem of how "states of consciousness can know" things, or objects;[25]: 465 by 1899 psychologists were busily studying the "contents of conscious experience by introspection and experiment."[26]: 365 Another popular metaphor was James's "doctrine of "the stream of consciousness", with its continuity, its "fringes and transitions"".[25]: vii [a]
James discussed the difficulties of describing and studying psychological phenomena, recognizing that commonly-used terminology was a necessary and acceptable starting point towards more precise, scientifically justified language. Prime examples were phrases like 'inner experience' and 'personal consciousness':
The first and foremost concrete fact which every one will affirm to belong to his inner experience is the fact that consciousness of some sort goes on. 'States of mind' succeed each other in him. [...] But everyone knows what the terms mean [only] in a rough way; [...] When I say every 'state' or 'thought' is part of a personal consciousness, 'personal consciousness' is one of the terms in question. Its meaning we know so long as no one asks us to define it, but to give an accurate account of it is the most difficult of philosophic tasks. [...] The only states of consciousness that we naturally deal with are found in personal consciousnesses, minds, selves, concrete particular I's and you's. [25]: 152-153
From introspection to awareness
In philosophy before the 20th century, consciousness as a phenomenon was the 'inner world' of 'one's own mind', and introspection was the mind "attending to" itself,[b] an activity seemingly distinct from that of perceiving the 'outer world' and its physical phenomena. In 1892 William James noted the distinction along with doubts about the "inward" character of the mind:
'Things' have been doubted, but thoughts and feelings have never been doubted. The outer world, but never the inner world, has been denied. Everyone assumes that we have direct introspective acquaintance with our thinking activity as such, with our consciousness as something inward and contrasted with the outer objects which it knows. Yet I must confess that for my part I cannot feel sure of this conclusion. ... It seems as if consciousness as an inner activity were rather a postulate than a sensibly given fact...[25]: 467
By the 1960s, for many philosophers and psychologists who talked about consciousness, the word no longer meant the 'inner world' but an indefinite, large category called awareness, as in the following example:
It is difficult for modern Western man to grasp that the Greeks really had no concept of consciousness in that they did not class together phenomena as varied as problem solving, remembering, imagining, perceiving, feeling pain, dreaming, and acting on the grounds that all these are manifestations of being aware or being conscious.[28]: 4
Many philosophers and scientists have been unhappy about the difficulty of producing a definition that does not involve circularity or fuzziness.[29] In The Macmillan Dictionary of Psychology (1989 edition), Stuart Sutherland emphasized external awareness, and expressed a skeptical attitude more than a definition:
Consciousness—The having of perceptions, thoughts, and feelings; awareness. The term is impossible to define except in terms that are unintelligible without a grasp of what consciousness means. Many fall into the trap of equating consciousness with self-consciousness—to be conscious it is only necessary to be aware of the external world. Consciousness is a fascinating but elusive phenomenon: it is impossible to specify what it is, what it does, or why it has evolved. Nothing worth reading has been written on it.[29]
Using 'awareness', however, as a definition or synonym of consciousness is not a simple matter:
If awareness of the environment . . . is the criterion of consciousness, then even the protozoans are conscious. If awareness of awareness is required, then it is doubtful whether the great apes and human infants are conscious.[26]
Influence on research
Many philosophers have argued that consciousness is a unitary concept that is understood by the majority of people despite the difficulty philosophers have had defining it.[30] Max Velmans proposed that the "everyday understanding of consciousness" uncontroversially "refers to experience itself rather than any particular thing that we observe or experience" and he added that consciousness "is [therefore] exemplified by all the things that we observe or experience",[31]: 4 whether thoughts, feelings, or perceptions. Velmans noted however, as of 2009, that there was a deep level of "confusion and internal division"[31] among experts about the phenomenon of consciousness, because researchers lacked "a sufficiently well-specified use of the term...to agree that they are investigating the same thing".[31]: 3 He argued additionally that "pre-existing theoretical commitments" to competing explanations of consciousness might be a source of bias.
Within the "modern consciousness studies" community the technical phrase 'phenomenal consciousness' is a common synonym for all forms of awareness, or simply 'experience',[31]: 4 without differentiating between inner and outer, or between higher and lower types. With advances in brain research, "the presence or absence of experienced phenomena"[31]: 3 of any kind underlies the work of those neuroscientists who seek "to analyze the precise relation of conscious phenomenology to its associated information processing" in the brain.[31]: 10 This neuroscientific goal is to find the "neural correlates of consciousness" (NCC). One criticism of this goal is that it begins with a theoretical commitment to the neurological origin of all "experienced phenomena" whether inner or outer.[c] Also, the fact that the easiest 'content of consciousness' to be so analyzed is "the experienced three-dimensional world (the phenomenal world) beyond the body surface"[31]: 4 invites another criticism, that most consciousness research since the 1990s, perhaps because of bias, has focused on processes of external perception.[33]
From a history of psychology perspective, Julian Jaynes rejected popular but "superficial views of consciousness"[2]: 447 especially those which equate it with "that vaguest of terms, experience".[24]: 8 In 1976 he insisted that if not for introspection, which for decades had been ignored or taken for granted rather than explained, there could be no "conception of what consciousness is"[24]: 18 and in 1990, he reaffirmed the traditional idea of the phenomenon called 'consciousness', writing that "its denotative definition is, as it was for Descartes, Locke, and Hume, what is introspectable".[2]: 450 Jaynes saw consciousness as an important but small part of human mentality, and he asserted: "there can be no progress in the science of consciousness until ... what is introspectable [is] sharply distinguished"[2]: 447 from the unconscious processes of cognition such as perception, reactive awareness and attention, and automatic forms of learning, problem-solving and decision-making.[24]: 21-47
The cognitive science point of view — with an inter-disciplinary perspective involving fields such as psychology, linguistics and anthropology[34] — requires no agreed definition of 'consciousness' but studies the interaction of many processes besides perception. For some researchers, consciousness is linked to some kind of "selfhood", for example to certain pragmatic issues such as the feeling of agency and the effects of regret[33] and action on 'self-experience' of one's own body or social identity.[35] Similarly Daniel Kahneman, who focused on systematic errors in perception, memory and decision-making, has differentiated between two kinds of mental processes, or cognitive "systems":[36] the "fast" activities that are primary, automatic and "cannot be turned off",[36]: 22 and the "slow", deliberate, effortful activities of a secondary system "often associated with the subjective experience of agency, choice, and concentration." [36]: 13 Kahneman's two systems have been described as "roughly corresponding to unconscious and conscious processes."[37]: 8 The two systems can interact, for example in sharing the control of attention.[36]: 22 While System 1 can be impulsive, "System 2 is in charge of self-control"[36]: 26 and "When we think of ourselves, we identify with System 2, the conscious, reasoning self that has beliefs, makes choices, and decides what to think about and what to do."[36]: 21
Some have argued that we should eliminate the concept from our understanding of the mind, a position known as consciousness semanticism.[38]
In medicine, a "level of consciousness" terminology is used to describe a patient's arousal and responsiveness, which can be seen as a continuum of states ranging from full alertness and comprehension, through disorientation, delirium, loss of meaningful communication, and finally loss of movement in response to painful stimuli.[39] Issues of practical concern include how the level of consciousness can be assessed in severely ill, comatose, or anesthetized people, and how to treat conditions in which consciousness is impaired or disrupted.[40] The degree or level of consciousness is measured by standardized behavior observation scales such as the Glasgow Coma Scale.
Philosophy of mind
Most writers on the philosophy of consciousness have been concerned with defending a particular point of view, and have organized their material accordingly. For surveys, the most common approach is to follow a historical path by associating stances with the philosophers who are most strongly associated with them, for example, Descartes, Locke, Kant, etc.[citation needed] An alternative is to organize philosophical stances according to basic issues.
Coherence of the concept
Philosophers differ from non-philosophers in their intuitions about what consciousness is.[41] While most people have a strong intuition for the existence of what they refer to as consciousness,[30] skeptics argue that this intuition is too narrow, either because the concept of consciousness is embedded in our intuitions, or because we all are illusions. Gilbert Ryle, for example, argued that traditional understanding of consciousness depends on a Cartesian dualist outlook that improperly distinguishes between mind and body, or between mind and world. He proposed that we speak not of minds, bodies, and the world, but of entities, or identities, acting in the world. Thus, by speaking of "consciousness" we end up leading ourselves by thinking that there is any sort of thing as consciousness separated from behavioral and linguistic understandings.[42]
Types
Ned Block argued that discussions on consciousness often failed to properly distinguish phenomenal (P-consciousness) from access (A-consciousness), though these terms had been used before Block.[43] P-consciousness, according to Block, is raw experience: it is moving, colored forms, sounds, sensations, emotions and feelings with our bodies and responses at the center. These experiences, considered independently of any impact on behavior, are called qualia. A-consciousness, on the other hand, is the phenomenon whereby information in our minds is accessible for verbal report, reasoning, and the control of behavior. So, when we perceive, information about what we perceive is access conscious; when we introspect, information about our thoughts is access conscious; when we remember, information about the past is access conscious, and so on. Although some philosophers, such as Daniel Dennett, have disputed the validity of this distinction,[44] others have broadly accepted it. David Chalmers has argued that A-consciousness can in principle be understood in mechanistic terms, but that understanding P-consciousness is much more challenging: he calls this the hard problem of consciousness.[45]
Some philosophers believe that Block's two types of consciousness are not the end of the story. William Lycan, for example, argued in his book Consciousness and Experience that at least eight clearly distinct types of consciousness can be identified (organism consciousness; control consciousness; consciousness of; state/event consciousness; reportability; introspective consciousness; subjective consciousness; self-consciousness)—and that even this list omits several more obscure forms.[46]
There is also debate over whether or not A-consciousness and P-consciousness always coexist or if they can exist separately. Although P-consciousness without A-consciousness is more widely accepted, there have been some hypothetical examples of A without P. Block, for instance, suggests the case of a "zombie" that is computationally identical to a person but without any subjectivity. However, he remains somewhat skeptical concluding "I don't know whether there are any actual cases of A-consciousness without P-consciousness, but I hope I have illustrated their conceptual possibility."[47]
Distinguishing consciousness from its contents
Sam Harris observes: "At the level of your experience, you are not a body of cells, organelles, and atoms; you are consciousness and its ever-changing contents".[48] Seen in this way, consciousness is a subjectively experienced, ever-present field in which things (the contents of consciousness) come and go.
Christopher Tricker argues that this field of consciousness is symbolized by the mythical bird that opens the Daoist classic the Zhuangzi. This bird's name is Of a Flock (peng 鵬), yet its back is countless thousands of miles across and its wings are like clouds arcing across the heavens. "Like Of a Flock, whose wings arc across the heavens, the wings of your consciousness span to the horizon. At the same time, the wings of every other being's consciousness span to the horizon. You are of a flock, one bird among kin."[49]
Mind–body problem
Main article: Mind–body problem
Illustration of dualism by René Descartes. Inputs are passed by the sensory organs to the pineal gland and from there to the immaterial spirit.
Mental processes (such as consciousness) and physical processes (such as brain events) seem to be correlated, however the specific nature of the connection is unknown.
The first influential philosopher to discuss this question specifically was Descartes, and the answer he gave is known as Cartesian dualism. Descartes proposed that consciousness resides within an immaterial domain he called res cogitans (the realm of thought), in contrast to the domain of material things, which he called res extensa (the realm of extension).[50] He suggested that the interaction between these two domains occurs inside the brain, perhaps in a small midline structure called the pineal gland.[51]
Although it is widely accepted that Descartes explained the problem cogently, few later philosophers have been happy with his solution, and his ideas about the pineal gland have especially been ridiculed.[52] However, no alternative solution has gained general acceptance. Proposed solutions can be divided broadly into two categories: dualist solutions that maintain Descartes's rigid distinction between the realm of consciousness and the realm of matter but give different answers for how the two realms relate to each other; and monist solutions that maintain that there is really only one realm of being, of which consciousness and matter are both aspects. Each of these categories itself contains numerous variants. The two main types of dualism are substance dualism (which holds that the mind is formed of a distinct type of substance not governed by the laws of physics) and property dualism (which holds that the laws of physics are universally valid but cannot be used to explain the mind). The three main types of monism are physicalism (which holds that the mind consists of matter organized in a particular way), idealism (which holds that only thought or experience truly exists, and matter is merely an illusion), and neutral monism (which holds that both mind and matter are aspects of a distinct essence that is itself identical to neither of them). There are also, however, a large number of idiosyncratic theories that cannot cleanly be assigned to any of these schools of thought.[53]
Since the dawn of Newtonian science with its vision of simple mechanical principles governing the entire universe, some philosophers have been tempted by the idea that consciousness could be explained in purely physical terms. The first influential writer to propose such an idea explicitly was Julien Offray de La Mettrie, in his book Man a Machine (L'homme machine). His arguments, however, were very abstract.[54] The most influential modern physical theories of consciousness are based on psychology and neuroscience. Theories proposed by neuroscientists such as Gerald Edelman[55] and Antonio Damasio,[56] and by philosophers such as Daniel Dennett,[57] seek to explain consciousness in terms of neural events occurring within the brain. Many other neuroscientists, such as Christof Koch,[58] have explored the neural basis of consciousness without attempting to frame all-encompassing global theories. At the same time, computer scientists working in the field of artificial intelligence have pursued the goal of creating digital computer programs that can simulate or embody consciousness.[59]
A few theoretical physicists have argued that classical physics is intrinsically incapable of explaining the holistic aspects of consciousness, but that quantum theory may provide the missing ingredients. Several theorists have therefore proposed quantum mind (QM) theories of consciousness.[60] Notable theories falling into this category include the holonomic brain theory of Karl Pribram and David Bohm, and the Orch-OR theory formulated by Stuart Hameroff and Roger Penrose. Some of these QM theories offer descriptions of phenomenal consciousness, as well as QM interpretations of access consciousness. None of the quantum mechanical theories have been confirmed by experiment. Recent publications by G. Guerreshi, J. Cia, S. Popescu, and H. Briegel[61] could falsify proposals such as those of Hameroff, which rely on quantum entanglement in protein. At the present time many scientists and philosophers consider the arguments for an important role of quantum phenomena to be unconvincing.[62] Empirical evidence is against the notion of quantum consciousness, an experiment about wave function collapse led by Catalina Curceanu in 2022 suggests that quantum consciousness, as suggested by Roger Penrose and Stuart Hameroff, is highly implausible.[63]
Apart from the general question of the "hard problem" of consciousness (which is, roughly speaking, the question of how mental experience can arise from a physical basis[64]), a more specialized question is how to square the subjective notion that we are in control of our decisions (at least in some small measure) with the customary view of causality that subsequent events are caused by prior events. The topic of free will is the philosophical and scientific examination of this conundrum.
Problem of other minds
Main article: Problem of other minds
Many philosophers consider experience to be the essence of consciousness, and believe that experience can only fully be known from the inside, subjectively. But if consciousness is subjective and not visible from the outside, why do the vast majority of people believe that other people are conscious, but rocks and trees are not?[65] This is called the problem of other minds.[66] It is particularly acute for people who believe in the possibility of philosophical zombies, that is, people who think it is possible in principle to have an entity that is physically indistinguishable from a human being and behaves like a human being in every way but nevertheless lacks consciousness.[67] Related issues have also been studied extensively by Greg Littmann of the University of Illinois,[68] and by Colin Allen (a professor at the University of Pittsburgh) regarding the literature and research studying artificial intelligence in androids.[69]
The most commonly given answer is that we attribute consciousness to other people because we see that they resemble us in appearance and behavior; we reason that if they look like us and act like us, they must be like us in other ways, including having experiences of the sort that we do.[70] There are, however, a variety of problems with that explanation. For one thing, it seems to violate the principle of parsimony, by postulating an invisible entity that is not necessary to explain what we observe.[70] Some philosophers, such as Daniel Dennett in a research paper titled "The Unimagined Preposterousness of Zombies", argue that people who give this explanation do not really understand what they are saying.[71] More broadly, philosophers who do not accept the possibility of zombies generally believe that consciousness is reflected in behavior (including verbal behavior), and that we attribute consciousness on the basis of behavior. A more straightforward way of saying this is that we attribute experiences to people because of what they can do, including the fact that they can tell us about their experiences.[72]
Scientific study
For many decades, consciousness as a research topic was avoided by the majority of mainstream scientists, because of a general feeling that a phenomenon defined in subjective terms could not properly be studied using objective experimental methods.[73] In 1975 George Mandler published an influential psychological study which distinguished between slow, serial, and limited conscious processes and fast, parallel and extensive unconscious ones.[74] The Science and Religion Forum[75] 1984 annual conference, 'From Artificial Intelligence to Human Consciousness' identified the nature of consciousness as a matter for investigation; Donald Michie was a keynote speaker. Starting in the 1980s, an expanding community of neuroscientists and psychologists have associated themselves with a field called Consciousness Studies, giving rise to a stream of experimental work published in books,[76] journals such as Consciousness and Cognition, Frontiers in Consciousness Research, Psyche, and the Journal of Consciousness Studies, along with regular conferences organized by groups such as the Association for the Scientific Study of Consciousness[77] and the Society for Consciousness Studies.
Modern medical and psychological investigations into consciousness are based on psychological experiments (including, for example, the investigation of priming effects using subliminal stimuli[78]), and on case studies of alterations in consciousness produced by trauma, illness, or drugs. Broadly viewed, scientific approaches are based on two core concepts. The first identifies the content of consciousness with the experiences that are reported by human subjects; the second makes use of the concept of consciousness that has been developed by neurologists and other medical professionals who deal with patients whose behavior is impaired. In either case, the ultimate goals are to develop techniques for assessing consciousness objectively in humans as well as other animals, and to understand the neural and psychological mechanisms that underlie it.[58]
Measurement
The Necker cube, an ambiguous image
Experimental research on consciousness presents special difficulties, due to the lack of a universally accepted operational definition. In the majority of experiments that are specifically about consciousness, the subjects are human, and the criterion used is verbal report: in other words, subjects are asked to describe their experiences, and their descriptions are treated as observations of the contents of consciousness.[79] For example, subjects who stare continuously at a Necker cube usually report that they experience it "flipping" between two 3D configurations, even though the stimulus itself remains the same.[80] The objective is to understand the relationship between the conscious awareness of stimuli (as indicated by verbal report) and the effects the stimuli have on brain activity and behavior. In several paradigms, such as the technique of response priming, the behavior of subjects is clearly influenced by stimuli for which they report no awareness, and suitable experimental manipulations can lead to increasing priming effects despite decreasing prime identification (double dissociation).[81]
Verbal report is widely considered to be the most reliable indicator of consciousness, but it raises a number of issues.[82] For one thing, if verbal reports are treated as observations, akin to observations in other branches of science, then the possibility arises that they may contain errors—but it is difficult to make sense of the idea that subjects could be wrong about their own experiences, and even more difficult to see how such an error could be detected.[83] Daniel Dennett has argued for an approach he calls heterophenomenology, which means treating verbal reports as stories that may or may not be true, but his ideas about how to do this have not been widely adopted.[84] Another issue with verbal report as a criterion is that it restricts the field of study to humans who have language: this approach cannot be used to study consciousness in other species, pre-linguistic children, or people with types of brain damage that impair language. As a third issue, philosophers who dispute the validity of the Turing test may feel that it is possible, at least in principle, for verbal report to be dissociated from consciousness entirely: a philosophical zombie may give detailed verbal reports of awareness in the absence of any genuine awareness.[85]
Although verbal report is in practice the "gold standard" for ascribing consciousness, it is not the only possible criterion.[82] In medicine, consciousness is assessed as a combination of verbal behavior, arousal, brain activity and purposeful movement. The last three of these can be used as indicators of consciousness when verbal behavior is absent.[86][87] The scientific literature regarding the neural bases of arousal and purposeful movement is very extensive. Their reliability as indicators of consciousness is disputed, however, due to numerous studies showing that alert human subjects can be induced to behave purposefully in a variety of ways in spite of reporting a complete lack of awareness.[81] Studies of the neuroscience of free will have also shown that the experiences that people report when they behave purposefully sometimes do not correspond to their actual behaviors or to the patterns of electrical activity recorded from their brains.[88]
Another approach applies specifically to the study of self-awareness, that is, the ability to distinguish oneself from others. In the 1970s Gordon Gallup developed an operational test for self-awareness, known as the mirror test. The test examines whether animals are able to differentiate between seeing themselves in a mirror versus seeing other animals. The classic example involves placing a spot of coloring on the skin or fur near the individual's forehead and seeing if they attempt to remove it or at least touch the spot, thus indicating that they recognize that the individual they are seeing in the mirror is themselves.[89] Humans (older than 18 months) and other great apes, bottlenose dolphins, orcas, pigeons, European magpies and elephants have all been observed to pass this test.[90]
Neural correlates
Schema of the neural processes underlying consciousness, from Christof Koch
A major part of the scientific literature on consciousness consists of studies that examine the relationship between the experiences reported by subjects and the activity that simultaneously takes place in their brains—that is, studies of the neural correlates of consciousness. The hope is to find that activity in a particular part of the brain, or a particular pattern of global brain activity, which will be strongly predictive of conscious awareness. Several brain imaging techniques, such as EEG and fMRI, have been used for physical measures of brain activity in these studies.[91]
Another idea that has drawn attention for several decades is that consciousness is associated with high-frequency (gamma band) oscillations in brain activity. This idea arose from proposals in the 1980s, by Christof von der Malsburg and Wolf Singer, that gamma oscillations could solve the so-called binding problem, by linking information represented in different parts of the brain into a unified experience.[92] Rodolfo Llinás, for example, proposed that consciousness results from recurrent thalamo-cortical resonance where the specific thalamocortical systems (content) and the non-specific (centromedial thalamus) thalamocortical systems (context) interact in the gamma band frequency via synchronous oscillations.[93]
A number of studies have shown that activity in primary sensory areas of the brain is not sufficient to produce consciousness: it is possible for subjects to report a lack of awareness even when areas such as the primary visual cortex (V1) show clear electrical responses to a stimulus.[94] Higher brain areas are seen as more promising, especially the prefrontal cortex, which is involved in a range of higher cognitive functions collectively known as executive functions.[95] There is substantial evidence that a "top-down" flow of neural activity (i.e., activity propagating from the frontal cortex to sensory areas) is more predictive of conscious awareness than a "bottom-up" flow of activity.[96] The prefrontal cortex is not the only candidate area, however: studies by Nikos Logothetis and his colleagues have shown, for example, that visually responsive neurons in parts of the temporal lobe reflect the visual perception in the situation when conflicting visual images are presented to different eyes (i.e., bistable percepts during binocular rivalry).[97] Furthermore, top-down feedback from higher to lower visual brain areas may be weaker or absent in the peripheral visual field, as suggested by some experimental data and theoretical arguments;[98] nevertheless humans can perceive visual inputs in the peripheral visual field arising from bottom-up V1 neural activities.[98][99] Meanwhile, bottom-up V1 activities for the central visual fields can be vetoed, and thus made invisible to perception, by the top-down feedback, when these bottom-up signals are inconsistent with the brain's internal model of the visual world.[98][99]
Modulation of neural responses may correlate with phenomenal experiences. In contrast to the raw electrical responses that do not correlate with consciousness, the modulation of these responses by other stimuli correlates surprisingly well with an important aspect of consciousness: namely with the phenomenal experience of stimulus intensity (brightness, contrast). In the research group of Danko Nikolić it has been shown that some of the changes in the subjectively perceived brightness correlated with the modulation of firing rates while others correlated with the modulation of neural synchrony.[100] An fMRI investigation suggested that these findings were strictly limited to the primary visual areas.[101] This indicates that, in the primary visual areas, changes in firing rates and synchrony can be considered as neural correlates of qualia—at least for some type of qualia.
In 2013, the perturbational complexity index (PCI) was proposed, a measure of the algorithmic complexity of the electrophysiological response of the cortex to transcranial magnetic stimulation. This measure was shown to be higher in individuals that are awake, in REM sleep or in a locked-in state than in those who are in deep sleep or in a vegetative state,[102] making it potentially useful as a quantitative assessment of consciousness states.
Assuming that not only humans but even some non-mammalian species are conscious, a number of evolutionary approaches to the problem of neural correlates of consciousness open up. For example, assuming that birds are conscious—a common assumption among neuroscientists and ethologists due to the extensive cognitive repertoire of birds—there are comparative neuroanatomical ways to validate some of the principal, currently competing, mammalian consciousness–brain theories. The rationale for such a comparative study is that the avian brain deviates structurally from the mammalian brain. So how similar are they? What homologs can be identified? The general conclusion from the study by Butler, et al.,[103] is that some of the major theories for the mammalian brain [104][105][106] also appear to be valid for the avian brain. The structures assumed to be critical for consciousness in mammalian brains have homologous counterparts in avian brains. Thus the main portions of the theories of Crick and Koch,[104] Edelman and Tononi,[105] and Cotterill [106] seem to be compatible with the assumption that birds are conscious. Edelman also differentiates between what he calls primary consciousness (which is a trait shared by humans and non-human animals) and higher-order consciousness as it appears in humans alone along with human language capacity.[105] Certain aspects of the three theories, however, seem less easy to apply to the hypothesis of avian consciousness. For instance, the suggestion by Crick and Koch that layer 5 neurons of the mammalian brain have a special role, seems difficult to apply to the avian brain, since the avian homologs have a different morphology. Likewise, the theory of Eccles[107][108] seems incompatible, since a structural homolog/analogue to the dendron has not been found in avian brains. The assumption of an avian consciousness also brings the reptilian brain into focus. The reason is the structural continuity between avian and reptilian brains, meaning that the phylogenetic origin of consciousness may be earlier than suggested by many leading neuroscientists.
Joaquin Fuster of UCLA has advocated the position of the importance of the prefrontal cortex in humans, along with the areas of Wernicke and Broca, as being of particular importance to the development of human language capacities neuro-anatomically necessary for the emergence of higher-order consciousness in humans.[109]
A study in 2016 looked at lesions in specific areas of the brainstem that were associated with coma and vegetative states. A small region of the rostral dorsolateral pontine tegmentum in the brainstem was suggested to drive consciousness through functional connectivity with two cortical regions, the left ventral anterior insular cortex, and the pregenual anterior cingulate cortex. These three regions may work together as a triad to maintain consciousness.[110]
Models
Further information: Models of consciousness
A wide range of empirical theories of consciousness have been proposed.[111][112][113] Adrian Doerig and colleagues list 13 notable theories,[113] while Anil Seth and Tim Bayne list 22 notable theories.[112]
Global workspace theory (GWT) is a cognitive architecture and theory of consciousness proposed by the cognitive psychologist Bernard Baars in 1988.[114] Baars explains the theory with the metaphor of a theater, with conscious processes represented by an illuminated stage.[114] This theater integrates inputs from a variety of unconscious and otherwise autonomous networks in the brain and then broadcasts them to unconscious networks (represented in the metaphor by a broad, unlit "audience").[114] The theory has since been expanded upon by other scientists including cognitive neuroscientist Stanislas Dehaene and Lionel Naccache.[115]
Integrated information theory (IIT) postulates that consciousness resides in the information being processed and arises once the information reaches a certain level of complexity.[116] Additionally, IIT is one of the only leading theories of consciousness that attempts to create a 1:1 mapping between conscious states and precise, formal mathematical descriptions of those mental states. Proponents of this model suggest that it may provide a physical grounding for consciousness in neurons, as they provide the mechanism by which information is integrated.[116]
Orchestrated objective reduction (Orch OR) postulates that consciousness originates at the quantum level inside neurons. The mechanism is held to be a quantum process called objective reduction that is orchestrated by cellular structures called microtubules. However the details of the mechanism would go beyond current quantum theory.[117]
In 2011, Graziano and Kastner[118] proposed the "attention schema" theory of awareness. In that theory, specific cortical areas, notably in the superior temporal sulcus and the temporo-parietal junction, are used to build the construct of awareness and attribute it to other people. The same cortical machinery is also used to attribute awareness to oneself. Damage to these cortical regions can lead to deficits in consciousness such as hemispatial neglect. In the attention schema theory, the value of explaining the feature of awareness and attributing it to a person is to gain a useful predictive model of that person's attentional processing. Attention is a style of information processing in which a brain focuses its resources on a limited set of interrelated signals. Awareness, in this theory, is a useful, simplified schema that represents attentional states. To be aware of X is explained by constructing a model of one's attentional focus on X.
The entropic brain is a theory of conscious states informed by neuroimaging research with psychedelic drugs. The theory suggests that the brain in primary states such as rapid eye movement (REM) sleep, early psychosis and under the influence of psychedelic drugs, is in a disordered state; normal waking consciousness constrains some of this freedom and makes possible metacognitive functions such as internal self-administered reality testing and self-awareness.[119][120][121][122] Criticism has included questioning whether the theory has been adequately tested.[123]
In 2017, work by David Rudrauf and colleagues, including Karl Friston, applied the active inference paradigm to consciousness, a model of how sensory data is integrated with priors in a process of projective transformation. The authors argue that, while their model identifies a key relationship between computation and phenomenology, it does not completely solve the hard problem of consciousness or completely close the explanatory gap.[124]
Biological function and evolution
Opinions are divided as to where in biological evolution consciousness emerged and about whether or not consciousness has any survival value. Some argue that consciousness is a byproduct of evolution. It has been argued that consciousness emerged (i) exclusively with the first humans, (ii) exclusively with the first mammals, (iii) independently in mammals and birds, or (iv) with the first reptiles.[125] Other authors date the origins of consciousness to the first animals with nervous systems or early vertebrates in the Cambrian over 500 million years ago.[126] Donald Griffin suggests in his book Animal Minds a gradual evolution of consciousness.[127] Each of these scenarios raises the question of the possible survival value of consciousness.
Thomas Henry Huxley defends in an essay titled "On the Hypothesis that Animals are Automata, and its History" an epiphenomenalist theory of consciousness according to which consciousness is a causally inert effect of neural activity—"as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery".[128] To this William James objects in his essay Are We Automata? by stating an evolutionary argument for mind-brain interaction implying that if the preservation and development of consciousness in the biological evolution is a result of natural selection, it is plausible that consciousness has not only been influenced by neural processes, but has had a survival value itself; and it could only have had this if it had been efficacious.[129][130] Karl Popper develops a similar evolutionary argument in the book The Self and Its Brain.[131]
Regarding the primary function of conscious processing, a recurring idea in recent theories is that phenomenal states somehow integrate neural activities and information-processing that would otherwise be independent.[132] This has been called the integration consensus. Another example has been proposed by Gerald Edelman called dynamic core hypothesis which puts emphasis on reentrant connections that reciprocally link areas of the brain in a massively parallel manner.[133] Edelman also stresses the importance of the evolutionary emergence of higher-order consciousness in humans from the historically older trait of primary consciousness which humans share with non-human animals (see Neural correlates section above). These theories of integrative function present solutions to two classic problems associated with consciousness: differentiation and unity. They show how our conscious experience can discriminate between a virtually unlimited number of different possible scenes and details (differentiation) because it integrates those details from our sensory systems, while the integrative nature of consciousness in this view easily explains how our experience can seem unified as one whole despite all of these individual parts. However, it remains unspecified which kinds of information are integrated in a conscious manner and which kinds can be integrated without consciousness. Nor is it explained what specific causal role conscious integration plays, nor why the same functionality cannot be achieved without consciousness. Obviously not all kinds of information are capable of being disseminated consciously (e.g., neural activity related to vegetative functions, reflexes, unconscious motor programs, low-level perceptual analyzes, etc.) and many kinds of information can be disseminated and combined with other kinds without consciousness, as in intersensory interactions such as the ventriloquism effect.[134] Hence it remains unclear why any of it is conscious. For a review of the differences between conscious and unconscious integrations, see the article of Ezequiel Morsella.[134]
As noted earlier, even among writers who consider consciousness to be well-defined, there is widespread dispute about which animals other than humans can be said to possess it.[135] Edelman has described this distinction as that of humans possessing higher-order consciousness while sharing the trait of primary consciousness with non-human animals (see previous paragraph). Thus, any examination of the evolution of consciousness is faced with great difficulties. Nevertheless, some writers have argued that consciousness can be viewed from the standpoint of evolutionary biology as an adaptation in the sense of a trait that increases fitness.[136] In his article "Evolution of consciousness", John Eccles argued that special anatomical and physical properties of the mammalian cerebral cortex gave rise to consciousness ("[a] psychon ... linked to [a] dendron through quantum physics").[137] Bernard Baars proposed that once in place, this "recursive" circuitry may have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms.[138] Peter Carruthers has put forth one such potential adaptive advantage gained by conscious creatures by suggesting that consciousness allows an individual to make distinctions between appearance and reality.[139] This ability would enable a creature to recognize the likelihood that their perceptions are deceiving them (e.g. that water in the distance may be a mirage) and behave accordingly, and it could also facilitate the manipulation of others by recognizing how things appear to them for both cooperative and devious ends.
Other philosophers, however, have suggested that consciousness would not be necessary for any functional advantage in evolutionary processes.[140][141] No one has given a causal explanation, they argue, of why it would not be possible for a functionally equivalent non-conscious organism (i.e., a philosophical zombie) to achieve the very same survival advantages as a conscious organism. If evolutionary processes are blind to the difference between function F being performed by conscious organism O and non-conscious organism O*, it is unclear what adaptive advantage consciousness could provide.[142] As a result, an exaptive explanation of consciousness has gained favor with some theorists that posit consciousness did not evolve as an adaptation but was an exaptation arising as a consequence of other developments such as increases in brain size or cortical rearrangement.[126] Consciousness in this sense has been compared to the blind spot in the retina where it is not an adaption of the retina, but instead just a by-product of the way the retinal axons were wired.[143] Several scholars including Pinker, Chomsky, Edelman, and Luria have indicated the importance of the emergence of human language as an important regulative mechanism of learning and memory in the context of the development of higher-order consciousness (see Neural correlates section above).
Altered states
A Buddhist monk meditating
Main article: Altered state of consciousness
There are some brain states in which consciousness seems to be absent, including dreamless sleep or coma. There are also a variety of circumstances that can change the relationship between the mind and the world in less drastic ways, producing what are known as altered states of consciousness. Some altered states occur naturally; others can be produced by drugs or brain damage.[144] Altered states can be accompanied by changes in thinking, disturbances in the sense of time, feelings of loss of control, changes in emotional expression, alternations in body image and changes in meaning or significance.[145]
The two most widely accepted altered states are sleep and dreaming. Although dream sleep and non-dream sleep appear very similar to an outside observer, each is associated with a distinct pattern of brain activity, metabolic activity, and eye movement; each is also associated with a distinct pattern of experience and cognition. During ordinary non-dream sleep, people who are awakened report only vague and sketchy thoughts, and their experiences do not cohere into a continuous narrative. During dream sleep, in contrast, people who are awakened report rich and detailed experiences in which events form a continuous progression, which may however be interrupted by bizarre or fantastic intrusions.[146][failed verification] Thought processes during the dream state frequently show a high level of irrationality. Both dream and non-dream states are associated with severe disruption of memory: it usually disappears in seconds during the non-dream state, and in minutes after awakening from a dream unless actively refreshed.[147]
Research conducted on the effects of partial epileptic seizures on consciousness found that patients who have partial epileptic seizures experience altered states of consciousness.[148][149] In partial epileptic seizures, consciousness is impaired or lost while some aspects of consciousness, often automated behaviors, remain intact. Studies found that when measuring the qualitative features during partial epileptic seizures, patients exhibited an increase in arousal and became absorbed in the experience of the seizure, followed by difficulty in focusing and shifting attention.
A variety of psychoactive drugs, including alcohol, have notable effects on consciousness.[150] These range from a simple dulling of awareness produced by sedatives, to increases in the intensity of sensory qualities produced by stimulants, cannabis, empathogens–entactogens such as MDMA ("Ecstasy"), or most notably by the class of drugs known as psychedelics.[144] LSD, mescaline, psilocybin, dimethyltryptamine, and others in this group can produce major distortions of perception, including hallucinations; some users even describe their drug-induced experiences as mystical or spiritual in quality. The brain mechanisms underlying these effects are not as well understood as those induced by use of alcohol,[150] but there is substantial evidence that alterations in the brain system that uses the chemical neurotransmitter serotonin play an essential role.[151]
There has been some research into physiological changes in yogis and people who practise various techniques of meditation. Some research with brain waves during meditation has reported differences between those corresponding to ordinary relaxation and those corresponding to meditation. It has been disputed, however, whether there is enough evidence to count these as physiologically distinct states of consciousness.[152]
The most extensive study of the characteristics of altered states of consciousness was made by psychologist Charles Tart in the 1960s and 1970s. Tart analyzed a state of consciousness as made up of a number of component processes, including exteroception (sensing the external world); interoception (sensing the body); input-processing (seeing meaning); emotions; memory; time sense; sense of identity; evaluation and cognitive processing; motor output; and interaction with the environment.[153][self-published source] Each of these, in his view, could be altered in multiple ways by drugs or other manipulations. The components that Tart identified have not, however, been validated by empirical studies. Research in this area has not yet reached firm conclusions, but a recent questionnaire-based study identified eleven significant factors contributing to drug-induced states of consciousness: experience of unity; spiritual experience; blissful state; insightfulness; disembodiment; impaired control and cognition; anxiety; complex imagery; elementary imagery; audio-visual synesthesia; and changed meaning of percepts.[154]
Medical aspects
The medical approach to consciousness is scientifically oriented. It derives from a need to treat people whose brain function has been impaired as a result of disease, brain damage, toxins, or drugs. In medicine, conceptual distinctions are considered useful to the degree that they can help to guide treatments. The medical approach focuses mostly on the amount of consciousness a person has: in medicine, consciousness is assessed as a "level" ranging from coma and brain death at the low end, to full alertness and purposeful responsiveness at the high end.[155]
Consciousness is of concern to patients and physicians, especially neurologists and anesthesiologists. Patients may have disorders of consciousness or may need to be anesthetized for a surgical procedure. Physicians may perform consciousness-related interventions such as instructing the patient to sleep, administering general anesthesia, or inducing medical coma.[155] Also, bioethicists may be concerned with the ethical implications of consciousness in medical cases of patients such as the Karen Ann Quinlan case,[156] while neuroscientists may study patients with impaired consciousness in hopes of gaining information about how the brain works.[157]
Assessment
In medicine, consciousness is examined using a set of procedures known as neuropsychological assessment.[86] There are two commonly used methods for assessing the level of consciousness of a patient: a simple procedure that requires minimal training, and a more complex procedure that requires substantial expertise. The simple procedure begins by asking whether the patient is able to move and react to physical stimuli. If so, the next question is whether the patient can respond in a meaningful way to questions and commands. If so, the patient is asked for name, current location, and current day and time. A patient who can answer all of these questions is said to be "alert and oriented times four" (sometimes denoted "A&Ox4" on a medical chart), and is usually considered fully conscious.[158]
The more complex procedure is known as a neurological examination, and is usually carried out by a neurologist in a hospital setting. A formal neurological examination runs through a precisely delineated series of tests, beginning with tests for basic sensorimotor reflexes, and culminating with tests for sophisticated use of language. The outcome may be summarized using the Glasgow Coma Scale, which yields a number in the range 3–15, with a score of 3 to 8 indicating coma, and 15 indicating full consciousness. The Glasgow Coma Scale has three subscales, measuring the best motor response (ranging from "no motor response" to "obeys commands"), the best eye response (ranging from "no eye opening" to "eyes opening spontaneously") and the best verbal response (ranging from "no verbal response" to "fully oriented"). There is also a simpler pediatric version of the scale, for children too young to be able to use language.[155]
In 2013, an experimental procedure was developed to measure degrees of consciousness, the procedure involving stimulating the brain with a magnetic pulse, measuring resulting waves of electrical activity, and developing a consciousness score based on the complexity of the brain activity.[159]
Disorders
Medical conditions that inhibit consciousness are considered disorders of consciousness.[160] This category generally includes minimally conscious state and persistent vegetative state, but sometimes also includes the less severe locked-in syndrome and more severe chronic coma.[160][161] Differential diagnosis of these disorders is an active area of biomedical research.[162][163][164] Finally, brain death results in possible irreversible disruption of consciousness.[160] While other conditions may cause a moderate deterioration (e.g., dementia and delirium) or transient interruption (e.g., grand mal and petit mal seizures) of consciousness, they are not included in this category.
Disorder Description
Locked-in syndrome The patient has awareness, sleep-wake cycles, and meaningful behavior (viz., eye-movement), but is isolated due to quadriplegia and pseudobulbar palsy.
Minimally conscious state The patient has intermittent periods of awareness and wakefulness and displays some meaningful behavior.
Persistent vegetative state The patient has sleep-wake cycles, but lacks awareness and only displays reflexive and non-purposeful behavior.
Chronic coma The patient lacks awareness and sleep-wake cycles and only displays reflexive behavior.
Brain death The patient lacks awareness, sleep-wake cycles, and brain-mediated reflexive behavior.
Medical experts increasingly view anosognosia as a disorder of consciousness.[165] Anosognosia is a Greek-derived term meaning "unawareness of disease". This is a condition in which patients are disabled in some way, most commonly as a result of a stroke, but either misunderstand the nature of the problem or deny that there is anything wrong with them.[166] The most frequently occurring form is seen in people who have experienced a stroke damaging the parietal lobe in the right hemisphere of the brain, giving rise to a syndrome known as hemispatial neglect, characterized by an inability to direct action or attention toward objects located to the left with respect to their bodies. Patients with hemispatial neglect are often paralyzed on the left side of the body, but sometimes deny being unable to move. When questioned about the obvious problem, the patient may avoid giving a direct answer, or may give an explanation that does not make sense. Patients with hemispatial neglect may also fail to recognize paralyzed parts of their bodies: one frequently mentioned case is of a man who repeatedly tried to throw his own paralyzed right leg out of the bed he was lying in, and when asked what he was doing, complained that somebody had put a dead leg into the bed with him. An even more striking type of anosognosia is Anton–Babinski syndrome, a rarely occurring condition in which patients become blind but claim to be able to see normally, and persist in this claim in spite of all evidence to the contrary.[167]
Outside human adults
In children
See also: Theory of mind
Of the eight types of consciousness in the Lycan classification, some are detectable in utero and others develop years after birth. Psychologist and educator William Foulkes studied children's dreams and concluded that prior to the shift in cognitive maturation that humans experience during ages five to seven,[168] children lack the Lockean consciousness that Lycan had labeled "introspective consciousness" and that Foulkes labels "self-reflection".[169] In a 2020 paper, Katherine Nelson and Robyn Fivush use "autobiographical consciousness" to label essentially the same faculty, and agree with Foulkes on the timing of this faculty's acquisition. Nelson and Fivush contend that "language is the tool by which humans create a new, uniquely human form of consciousness, namely, autobiographical consciousness."[170] Julian Jaynes had staked out these positions decades earlier.[171][172] Citing the developmental steps that lead the infant to autobiographical consciousness, Nelson and Fivush point to the acquisition of "theory of mind", calling theory of mind "necessary for autobiographical consciousness" and defining it as "understanding differences between one's own mind and others' minds in terms of beliefs, desires, emotions and thoughts." They write, "The hallmark of theory of mind, the understanding of false belief, occurs ... at five to six years of age."[173]
In animals
Main article: Animal consciousness
The topic of animal consciousness is beset by a number of difficulties. It poses the problem of other minds in an especially severe form, because non-human animals, lacking the ability to express human language, cannot tell humans about their experiences.[174] Also, it is difficult to reason objectively about the question, because a denial that an animal is conscious is often taken to imply that it does not feel, its life has no value, and that harming it is not morally wrong. Descartes, for example, has sometimes been blamed for mistreatment of animals due to the fact that he believed only humans have a non-physical mind.[175] Most people have a strong intuition that some animals, such as cats and dogs, are conscious, while others, such as insects, are not; but the sources of this intuition are not obvious, and are often based on personal interactions with pets and other animals they have observed.[174]
Thomas Nagel argues that while a human might be able to imagine what it is like to be a bat by taking "the bat's point of view", it would still be impossible "to know what it is like for a bat to be a bat." (Townsend's big-eared bat pictured).
Philosophers who consider subjective experience the essence of consciousness also generally believe, as a correlate, that the existence and nature of animal consciousness can never rigorously be known. Thomas Nagel spelled out this point of view in an influential essay titled What Is it Like to Be a Bat?. He said that an organism is conscious "if and only if there is something that it is like to be that organism—something it is like for the organism"; and he argued that no matter how much we know about an animal's brain and behavior, we can never really put ourselves into the mind of the animal and experience its world in the way it does itself.[176] Other thinkers, such as Douglas Hofstadter, dismiss this argument as incoherent.[177] Several psychologists and ethologists have argued for the existence of animal consciousness by describing a range of behaviors that appear to show animals holding beliefs about things they cannot directly perceive—Donald Griffin's 2001 book Animal Minds reviews a substantial portion of the evidence.[127]
On July 7, 2012, eminent scientists from different branches of neuroscience gathered at the University of Cambridge to celebrate the Francis Crick Memorial Conference, which deals with consciousness in humans and pre-linguistic consciousness in nonhuman animals. After the conference, they signed in the presence of Stephen Hawking, the 'Cambridge Declaration on Consciousness', which summarizes the most important findings of the survey:
"We decided to reach a consensus and make a statement directed to the public that is not scientific. It's obvious to everyone in this room that animals have consciousness, but it is not obvious to the rest of the world. It is not obvious to the rest of the Western world or the Far East. It is not obvious to the society."[178]
"Convergent evidence indicates that non-human animals ..., including all mammals and birds, and other creatures, ... have the necessary neural substrates of consciousness and the capacity to exhibit intentional behaviors."[179]
In artificial intelligence
Main article: Artificial consciousness
The idea of an artifact made conscious is an ancient theme of mythology, appearing for example in the Greek myth of Pygmalion, who carved a statue that was magically brought to life, and in medieval Jewish stories of the Golem, a magically animated homunculus built of clay.[180] However, the possibility of actually constructing a conscious machine was probably first discussed by Ada Lovelace, in a set of notes written in 1842 about the Analytical Engine invented by Charles Babbage, a precursor (never built) to modern electronic computers. Lovelace was essentially dismissive of the idea that a machine such as the Analytical Engine could think in a humanlike way. She wrote:
It is desirable to guard against the possibility of exaggerated ideas that might arise as to the powers of the Analytical Engine. ... The Analytical Engine has no pretensions whatever to originate anything. It can do whatever we know how to order it to perform. It can follow analysis; but it has no power of anticipating any analytical relations or truths. Its province is to assist us in making available what we are already acquainted with.[181]
One of the most influential contributions to this question was an essay written in 1950 by pioneering computer scientist Alan Turing, titled Computing Machinery and Intelligence. Turing disavowed any interest in terminology, saying that even "Can machines think?" is too loaded with spurious connotations to be meaningful; but he proposed to replace all such questions with a specific operational test, which has become known as the Turing test.[182] To pass the test, a computer must be able to imitate a human well enough to fool interrogators. In his essay Turing discussed a variety of possible objections, and presented a counterargument to each of them. The Turing test is commonly cited in discussions of artificial intelligence as a proposed criterion for machine consciousness; it has provoked a great deal of philosophical debate. For example, Daniel Dennett and Douglas Hofstadter argue that anything capable of passing the Turing test is necessarily conscious,[183] while David Chalmers argues that a philosophical zombie could pass the test, yet fail to be conscious.[184] A third group of scholars have argued that with technological growth once machines begin to display any substantial signs of human-like behavior then the dichotomy (of human consciousness compared to human-like consciousness) becomes passé and issues of machine autonomy begin to prevail even as observed in its nascent form within contemporary industry and technology.[68][69] Jürgen Schmidhuber argues that consciousness is the result of compression.[185] As an agent sees representation of itself recurring in the environment, the compression of this representation can be called consciousness.
John Searle in December 2005
In a lively exchange over what has come to be referred to as "the Chinese room argument", John Searle sought to refute the claim of proponents of what he calls "strong artificial intelligence (AI)" that a computer program can be conscious, though he does agree with advocates of "weak AI" that computer programs can be formatted to "simulate" conscious states. His own view is that consciousness has subjective, first-person causal powers by being essentially intentional due to the way human brains function biologically; conscious persons can perform computations, but consciousness is not inherently computational the way computer programs are. To make a Turing machine that speaks Chinese, Searle imagines a room with one monolingual English speaker (Searle himself, in fact), a book that designates a combination of Chinese symbols to be output paired with Chinese symbol input, and boxes filled with Chinese symbols. In this case, the English speaker is acting as a computer and the rulebook as a program. Searle argues that with such a machine, he would be able to process the inputs to outputs perfectly without having any understanding of Chinese, nor having any idea what the questions and answers could possibly mean. If the experiment were done in English, since Searle knows English, he would be able to take questions and give answers without any algorithms for English questions, and he would be effectively aware of what was being said and the purposes it might serve. Searle would pass the Turing test of answering the questions in both languages, but he is only conscious of what he is doing when he speaks English. Another way of putting the argument is to say that computer programs can pass the Turing test for processing the syntax of a language, but that the syntax cannot lead to semantic meaning in the way strong AI advocates hoped.[186][187]
In the literature concerning artificial intelligence, Searle's essay has been second only to Turing's in the volume of debate it has generated.[188] Searle himself was vague about what extra ingredients it would take to make a machine conscious: all he proposed was that what was needed was "causal powers" of the sort that the brain has and that computers lack. But other thinkers sympathetic to his basic argument have suggested that the necessary (though perhaps still not sufficient) extra conditions may include the ability to pass not just the verbal version of the Turing test, but the robotic version,[189] which requires grounding the robot's words in the robot's sensorimotor capacity to categorize and interact with the things in the world that its words are about, Turing-indistinguishably from a real person. Turing-scale robotics is an empirical branch of research on embodied cognition and situated cognition.[190]
In 2014, Victor Argonov has suggested a non-Turing test for machine consciousness based on a machine's ability to produce philosophical judgments.[191] He argues that a deterministic machine must be regarded as conscious if it is able to produce judgments on all problematic properties of consciousness (such as qualia or binding) having no innate (preloaded) philosophical knowledge on these issues, no philosophical discussions while learning, and no informational models of other creatures in its memory (such models may implicitly or explicitly contain knowledge about these creatures' consciousness). However, this test can be used only to detect, but not refute the existence of consciousness. A positive result proves that a machine is conscious but a negative result proves nothing. For example, absence of philosophical judgments may be caused by lack of the machine's intellect, not by absence of consciousness.
Stream of consciousness
Main article: Stream of consciousness (psychology)
William James is usually credited with popularizing the idea that human consciousness flows like a stream, in his Principles of Psychology of 1890.
According to James, the "stream of thought" is governed by five characteristics:[192]
Every thought tends to be part of a personal consciousness.
Within each personal consciousness thought is always changing.
Within each personal consciousness thought is sensibly continuous.
It always appears to deal with objects independent of itself.
It is interested in some parts of these objects to the exclusion of others.
A similar concept appears in Buddhist philosophy, expressed by the Sanskrit term Citta-saṃtāna, which is usually translated as mindstream or "mental continuum". Buddhist teachings describe that consciousness manifests moment to moment as sense impressions and mental phenomena that are continuously changing.[193] The teachings list six triggers that can result in the generation of different mental events.[193] These triggers are input from the five senses (seeing, hearing, smelling, tasting or touch sensations), or a thought (relating to the past, present or the future) that happen to arise in the mind. The mental events generated as a result of these triggers are: feelings, perceptions and intentions/behaviour. The moment-by-moment manifestation of the mind-stream is said to happen in every person all the time. It even happens in a scientist who analyzes various phenomena in the world, or analyzes the material body including the organ brain.[193] The manifestation of the mindstream is also described as being influenced by physical laws, biological laws, psychological laws, volitional laws, and universal laws.[193] The purpose of the Buddhist practice of mindfulness is to understand the inherent nature of the consciousness and its characteristics.[194]
Narrative form
In the West, the primary impact of the idea has been on literature rather than science: "stream of consciousness as a narrative mode" means writing in a way that attempts to portray the moment-to-moment thoughts and experiences of a character. This technique perhaps had its beginnings in the monologs of Shakespeare's plays and reached its fullest development in the novels of James Joyce and Virginia Woolf, although it has also been used by many other noted writers.[195]
Here, for example, is a passage from Joyce's Ulysses about the thoughts of Molly Bloom:
Yes because he never did a thing like that before as ask to get his breakfast in bed with a couple of eggs since the City Arms hotel when he used to be pretending to be laid up with a sick voice doing his highness to make himself interesting for that old faggot Mrs Riordan that he thought he had a great leg of and she never left us a farthing all for masses for herself and her soul greatest miser ever was actually afraid to lay out 4d for her methylated spirit telling me all her ailments she had too much old chat in her about politics and earthquakes and the end of the world let us have a bit of fun first God help the world if all the women were her sort down on bathingsuits and lownecks of course nobody wanted her to wear them I suppose she was pious because no man would look at her twice I hope Ill never be like her a wonder she didnt want us to cover our faces but she was a welleducated woman certainly and her gabby talk about Mr Riordan here and Mr Riordan there I suppose he was glad to get shut of her.[196]
Spiritual approaches
Further information: Higher consciousness
To most philosophers, the word "consciousness" connotes the relationship between the mind and the world.[citation needed] To writers on spiritual or religious topics, it frequently connotes the relationship between the mind and God, or the relationship between the mind and deeper truths that are thought to be more fundamental than the physical world.[citation needed]
The Canadian psychiatrist Richard Maurice Bucke, author of the 1901 book Cosmic Consciousness: A Study in the Evolution of the Human Mind, distinguished between three types of consciousness: 'Simple Consciousness', awareness of the body, possessed by many animals; 'Self Consciousness', awareness of being aware, possessed only by humans; and 'Cosmic Consciousness', awareness of the life and order of the universe, possessed only by humans who have attained "intellectual enlightenment or illumination".[197][third-party source needed]
Another thorough account of the spiritual approach is Ken Wilber's 1977 book The Spectrum of Consciousness, a comparison of western and eastern ways of thinking about the mind. Wilber described consciousness as a spectrum with ordinary awareness at one end, and more profound types of awareness at higher levels.[198][third-party source needed]
Other examples include the various levels of spiritual consciousness presented by Prem Saran Satsangi and Stuart Hameroff.[199][third-party source needed]
See also
Bicameral mentality – Hypothesis in psychology
Chaitanya – Hindu philosophical concept
Claustrum – Structure in the brain
Habenula – Small bilateral neuronal structure in the brain of vertebrates
Models of consciousness – Aspect of consciousness research
Plant perception – Paranormal idea that plants are sentient
Sakshi – Pure awareness in Hindu philosophy
Vertiginous question – Philosophical argument by Benj Hellie
Notes
From the introduction by Ralph Barton Perry, 1948.
From the Macmillan Encyclopedia of Philosophy (1967): "Locke's use of 'consciousness' was widely adopted in British philosophy. In the late nineteenth century the term 'introspection' began to be used. G. F. Stout's definition is typical: "To introspect is to attend to the workings of one's own mind" [... (1899)]."[27]: 191–192
"Investigating "how experience ensues from the brain", rather than exploring a factual claim, betrays a philosophical commitment."[32]
References
"consciousness". Merriam-Webster. Retrieved June 4, 2012.
Jaynes J (2000) [1976]. The Origin of Consciousness in the Breakdown of the Bicameral Mind. Houghton Mifflin. ISBN 0-618-05707-2.
Rochat P (2003). "Five levels of self-awareness as they unfold early in life" (PDF). Consciousness and Cognition. 12 (4): 717–731. doi:10.1016/s1053-8100(03)00081-3. PMID 14656513. S2CID 10241157. Archived (PDF) from the original on 2022-10-09.
P.A. Guertin (2019). "A novel concept introducing the idea of continuously changing levels of consciousness". Journal of Consciousness Exploration & Research. 10 (6): 406–412. Archived from the original on 2021-12-15. Retrieved 2021-08-19.
Hacker P (2012). "The Sad and Sorry History of Consciousness: being, among other things, a challenge to the "consciousness-studies community"" (PDF). Royal Institute of Philosophy. supplementary volume 70. Archived (PDF) from the original on 2022-10-09.
Barfield O (1962) [1926]. History in English Words (239 pgs. paper covered ed.). London: Faber and Faber Limited.
C. S. Lewis (1990). "Ch. 8: Conscience and conscious". Studies in words. Cambridge University Press. ISBN 978-0-521-39831-2.
Thomas Hobbes (1904). Leviathan: or, The Matter, Forme & Power of a Commonwealth, Ecclesiasticall and Civill. University Press. p. 39. ISBN 9783932392382.
James Ussher, Charles Richard Elrington (1613). The whole works, Volume 2. Hodges and Smith. p. 417.
Barbara Cassin (2014). Dictionary of Untranslatables. A Philosophical Lexicon. Princeton University Press. p. 176. ISBN 978-0-691-13870-1.
G. Molenaar (1969). "Seneca's Use of the Term Conscientia". Mnemosyne. 22 (2): 170–180. doi:10.1163/156852569x00670.
affecting the heart valves (e.g. congenital aortic stenosis), or the main blood vessels that lead from the heart (e.g. coarctation of the aorta). More complex syndromes are seen that affect more than one part of the heart (e.g. Tetralogy of Fallot).
Some congenital heart defects allow blood that is low in oxygen that would normally be returned to the lungs to instead be pumped back to the rest of the body. These are known as cyanotic congenital heart defects and are often more serious. Major congenital heart defects are often picked up in childhood, shortly after birth, or even before a child is born (e.g. transposition of the great arteries), causing breathlessness and a lower rate of growth. More minor forms of congenital heart disease may remain undetected for many years and only reveal themselves in adult life (e.g., atrial septal defect).[67][68]
Channelopathies
Main article: Channelopathy
Channelopathies can be categorized based on the organ system they affect. In the cardiovascular system, the electrical impulse required for each heart beat is provided by the electrochemical gradient of each heart cell. Because the beating of the heart depends on the proper movement of ions across the surface membrane, cardiac ion channelopathies form a major group of heart diseases.[69][70] Cardiac ion channelopathies may explain some of the cases of sudden death syndrome and sudden arrhythmic death syndrome.[71] Long QT syndrome is the most common form of cardiac channelopathy.
Long QT Syndrome (LQTS) - Mostly hereditary. On EKG can be observed as longer corrected QT interval (QTc). Characterized by fainting, sudden, life-threatening heart rhythm disturbances - Torsades de pointes type ventricular tachycardia, ventricular fibrillation and risk of sudden cardiac death.[72]
Short QT syndrome.
Catecholaminergic polymorphic ventricular tachycardia (CPVT).[73]
Progressive cardiac conduction defect (PCCD).[74]
Early repolarisation syndrome (BER) - common in younger and active people, especially men, because it is affected by higher testosterone levels, which cause increased potassium currents, which further causes an elevation of the J-point on the EKG. In very rare cases, it can lead to ventricular fibrillation and death.[75]
Brugada syndrome - a genetic disorder characterized by an abnormal EKG and is one of the most common causes of sudden cardiac death in young men.[76]
Diagnosis
Heart disease is diagnosed by the taking of a medical history, a cardiac examination, and further investigations, including blood tests, echocardiograms, electrocardiograms, and imaging. Other invasive procedures such as cardiac catheterisation can also play a role.[77]
Examination
Main articles: Cardiac examination and Heart sounds
The cardiac examination includes inspection, feeling the chest with the hands (palpation) and listening with a stethoscope (auscultation).[78][79] It involves assessment of signs that may be visible on a person's hands (such as splinter haemorrhages), joints and other areas. A person's pulse is taken, usually at the radial artery near the wrist, in order to assess for the rhythm and strength of the pulse. The blood pressure is taken, using either a manual or automatic sphygmomanometer or using a more invasive measurement from within the artery. Any elevation of the jugular venous pulse is noted. A person's chest is felt for any transmitted vibrations from the heart, and then listened to with a stethoscope.
Heart sounds
3D echocardiogram showing the mitral valve (right), tricuspid and mitral valves (top left) and aortic valve (top right).
The closure of the heart valves causes the heart sounds.
Normal heart sounds
Duration: 20 seconds.0:20
Normal heart sounds as heard with a stethoscope
Problems playing this file? See media help.
Typically, healthy hearts have only two audible heart sounds, called S1 and S2. The first heart sound S1, is the sound created by the closing of the atrioventricular valves during ventricular contraction and is normally described as "lub". The second heart sound, S2, is the sound of the semilunar valves closing during ventricular diastole and is described as "dub".[7] Each sound consists of two components, reflecting the slight difference in time as the two valves close.[80] S2 may split into two distinct sounds, either as a result of inspiration or different valvular or cardiac problems.[80] Additional heart sounds may also be present and these give rise to gallop rhythms. A third heart sound, S3 usually indicates an increase in ventricular blood volume. A fourth heart sound S4 is referred to as an atrial gallop and is produced by the sound of blood being forced into a stiff ventricle. The combined presence of S3 and S4 give a quadruple gallop.[7] Heart murmurs are abnormal heart sounds which can be either related to disease or benign, and there are several kinds.[81] There are normally two heart sounds, and abnormal heart sounds can either be extra sounds, or "murmurs" related to the flow of blood between the sounds. Murmurs are graded by volume, from 1 (the quietest), to 6 (the loudest), and evaluated by their relationship to the heart sounds, position in the cardiac cycle, and additional features such as their radiation to other sites, changes with a person's position, the frequency of the sound as determined by the side of the stethoscope by which they are heard, and site at which they are heard loudest.[81] Murmurs may be caused by damaged heart valves or congenital heart disease such as ventricular septal defects, or may be heard in normal hearts. A different type of sound, a pericardial friction rub can be heard in cases of pericarditis where the inflamed membranes can rub together.
Blood tests
Blood tests play an important role in the diagnosis and treatment of many cardiovascular conditions.
Troponin is a sensitive biomarker for a heart with insufficient blood supply. It is released 4–6 hours after injury and usually peaks at about 12–24 hours.[43] Two tests of troponin are often taken—one at the time of initial presentation and another within 3–6 hours,[82] with either a high level or a significant rise being diagnostic. A test for brain natriuretic peptide (BNP) can be used to evaluate for the presence of heart failure, and rises when there is increased demand on the left ventricle. These tests are considered biomarkers because they are highly specific for cardiac disease.[83] Testing for the MB form of creatine kinase provides information about the heart's blood supply, but is used less frequently because it is less specific and sensitive.[84]
Other blood tests are often taken to help understand a person's general health and risk factors that may contribute to heart disease. These often include a full blood count investigating for anaemia, and basic metabolic panel that may reveal any disturbances in electrolytes. A coagulation screen is often required to ensure that the right level of anticoagulation is given. Fasting lipids and fasting blood glucose (or an HbA1c level) are often ordered to evaluate a person's cholesterol and diabetes status, respectively.[85]
Electrocardiogram
Main article: Electrocardiography
Cardiac cycle shown against ECG
Using surface electrodes on the body, it is possible to record the electrical activity of the heart. This tracing of the electrical signal is the electrocardiogram (ECG) or (EKG). An ECG is a bedside test and involves the placement of ten leads on the body. This produces a "12 lead" ECG (three extra leads are calculated mathematically, and one lead is electrically ground, or earthed).[86]
There are five prominent features on the ECG: the P wave (atrial depolarisation), the QRS complex (ventricular depolarisation)[h] and the T wave (ventricular repolarisation).[7] As the heart cells contract, they create a current that travels through the heart. A downward deflection on the ECG implies cells are becoming more positive in charge ("depolarising") in the direction of that lead, whereas an upward inflection implies cells are becoming more negative ("repolarising") in the direction of the lead. This depends on the position of the lead, so if a wave of depolarising moved from left to right, a lead on the left would show a negative deflection, and a lead on the right would show a positive deflection. The ECG is a useful tool in detecting rhythm disturbances and in detecting insufficient blood supply to the heart.[86] Sometimes abnormalities are suspected, but not immediately visible on the ECG. Testing when exercising can be used to provoke an abnormality or an ECG can be worn for a longer period such as a 24-hour Holter monitor if a suspected rhythm abnormality is not present at the time of assessment.[86]
Imaging
Main article: Cardiac imaging
Several imaging methods can be used to assess the anatomy and function of the heart, including ultrasound (echocardiography), angiography, CT, MRI, and PET, scans. An echocardiogram is an ultrasound of the heart used to measure the heart's function, assess for valve disease, and look for any abnormalities. Echocardiography can be conducted by a probe on the chest (transthoracic), or by a probe in the esophagus (transesophageal). A typical echocardiography report will include information about the width of the valves noting any stenosis, whether there is any backflow of blood (regurgitation) and information about the blood volumes at the end of systole and diastole, including an ejection fraction, which describes how much blood is ejected from the left and right ventricles after systole. Ejection fraction can then be obtained by dividing the volume ejected by the heart (stroke volume) by the volume of the filled heart (end-diastolic volume).[87] Echocardiograms can also be conducted under circumstances when the body is more stressed, in order to examine for signs of lack of blood supply. This cardiac stress test involves either direct exercise, or where this is not possible, injection of a drug such as dobutamine.[79]
CT scans, chest X-rays and other forms of imaging can help evaluate the heart's size, evaluate for signs of pulmonary oedema, and indicate whether there is fluid around the heart. They are also useful for evaluating the aorta, the major blood vessel which leaves the heart.[79]
Treatment
Diseases affecting the heart can be treated by a variety of methods including lifestyle modification, drug treatment, and surgery.
Ischemic heart disease
Main articles: Coronary artery disease, Coronary artery bypass surgery, and Coronary stent
Narrowings of the coronary arteries (ischemic heart disease) are treated to relieve symptoms of chest pain caused by a partially narrowed artery (angina pectoris), to minimise heart muscle damage when an artery is completely occluded (myocardial infarction), or to prevent a myocardial infarction from occurring. Medications to improve angina symptoms include nitroglycerin, beta blockers, and calcium channel blockers, while preventative treatments include antiplatelets such as aspirin and statins, lifestyle measures such as stopping smoking and weight loss, and treatment of risk factors such as high blood pressure and diabetes.[88]
In addition to using medications, narrowed heart arteries can be treated by expanding the narrowings or redirecting the flow of blood to bypass an obstruction. This may be performed using a percutaneous coronary intervention, during which narrowings can be expanded by passing small balloon-tipped wires into the coronary arteries, inflating the balloon to expand the narrowing, and sometimes leaving behind a metal scaffold known as a stent to keep the artery open.[89]
If the narrowings in coronary arteries are unsuitable for treatment with a percutaneous coronary intervention, open surgery may be required. A coronary artery bypass graft can be performed, whereby a blood vessel from another part of the body (the saphenous vein, radial artery, or internal mammary artery) is used to redirect blood from a point before the narrowing (typically the aorta) to a point beyond the obstruction.[89][90]
Valvular heart disease
Main article: Artificial heart valve
Diseased heart valves that have become abnormally narrow or abnormally leaky may require surgery. This is traditionally performed as an open surgical procedure to replace the damaged heart valve with a tissue or metallic prosthetic valve. In some circumstances, the tricuspid or mitral valves can be repaired surgically, avoiding the need for a valve replacement. Heart valves can also be treated percutaneously, using techniques that share many similarities with percutaneous coronary intervention. Transcatheter aortic valve replacement is increasingly used for patients consider very high risk for open valve replacement.[61]
Cardiac arrhythmias
Main articles: Heart arrhythmia, Radiofrequency ablation, and Artificial cardiac pacemaker
Abnormal heart rhythms (arrhythmias) can be treated using antiarrhythmic drugs. These may work by manipulating the flow of electrolytes across the cell membrane (such as calcium channel blockers, sodium channel blockers, amiodarone, or digoxin), or modify the autonomic nervous system's effect on the heart (beta blockers and atropine). In some arrhythmias such as atrial fibrillation which increase the risk of stroke, this risk can be reduced using anticoagulants such as warfarin or novel oral anticoagulants.[63]
If medications fail to control an arrhythmia, another treatment option may be catheter ablation. In these procedures, wires are passed from a vein or artery in the leg to the heart to find the abnormal area of tissue that is causing the arrhythmia. The abnormal tissue can be intentionally damaged, or ablated, by heating or freezing to prevent further heart rhythm disturbances. Whilst the majority of arrhythmias can be treated using minimally invasive catheter techniques, some arrhythmias (particularly atrial fibrillation) can also be treated using open or thoracoscopic surgery, either at the time of other cardiac surgery or as a standalone procedure. A cardioversion, whereby an electric shock is used to stun the heart out of an abnormal rhythm, may also be used.
Cardiac devices in the form of pacemakers or implantable defibrillators may also be required to treat arrhythmias. Pacemakers, comprising a small battery powered generator implanted under the skin and one or more leads that extend to the heart, are most commonly used to treat abnormally slow heart rhythms.[64] Implantable defibrillators are used to treat serious life-threatening rapid heart rhythms. These devices monitor the heart, and if dangerous heart racing is detected can automatically deliver a shock to restore the heart to a normal rhythm. Implantable defibrillators are most commonly used in patients with heart failure, cardiomyopathies, or inherited arrhythmia syndromes.
Heart failure
Main article: Heart failure
As well as addressing the underlying cause for a patient's heart failure (most commonly ischemic heart disease or hypertension), the mainstay of heart failure treatment is with medication. These include drugs to prevent fluid from accumulating in the lungs by increasing the amount of urine a patient produces (diuretics), and drugs that attempt to preserve the pumping function of the heart (beta blockers, ACE inhibitors and mineralocorticoid receptor antagonists).[60]
In some patients with heart failure, a specialised pacemaker known as cardiac resynchronisation therapy can be used to improve the heart's pumping efficiency.[64] These devices are frequently combined with a defibrillator. In very severe cases of heart failure, a small pump called a ventricular assist device may be implanted which supplements the heart's own pumping ability. In the most severe cases, a cardiac transplant may be considered.[60]
History
Ancient
Heart and its blood vessels, by Leonardo da Vinci, 15th century
Humans have known about the heart since ancient times, although its precise function and anatomy were not clearly understood.[91] From the primarily religious views of earlier societies towards the heart, ancient Greeks are considered to have been the primary seat of scientific understanding of the heart in the ancient world.[92][93][94] Aristotle considered the heart to be the organ responsible for creating blood; Plato considered the heart as the source of circulating blood and Hippocrates noted blood circulating cyclically from the body through the heart to the lungs.[92][94] Erasistratos (304–250 BCE) noted the heart as a pump, causing dilation of blood vessels, and noted that arteries and veins both radiate from the heart, becoming progressively smaller with distance, although he believed they were filled with air and not blood. He also discovered the heart valves.[92]
The Greek physician Galen (2nd century CE) knew blood vessels carried blood and identified venous (dark red) and arterial (brighter and thinner) blood, each with distinct and separate functions.[92] Galen, noting the heart as the hottest organ in the body, concluded that it provided heat to the body.[94] The heart did not pump blood around, the heart's motion sucked blood in during diastole and the blood moved by the pulsation of the arteries themselves.[94] Galen believed the arterial blood was created by venous blood passing from the left ventricle to the right through 'pores' between the ventricles.[91] Air from the lungs passed from the lungs via the pulmonary artery to the left side of the heart and created arterial blood.[94]
These ideas went unchallenged for almost a thousand years.[91][94]
Pre-modern
The earliest descriptions of the coronary and pulmonary circulation systems can be found in the Commentary on Anatomy in Avicenna's Canon, published in 1242 by Ibn al-Nafis.[95] In his manuscript, al-Nafis wrote that blood passes through the pulmonary circulation instead of moving from the right to the left ventricle as previously believed by Galen.[96] His work was later translated into Latin by Andrea Alpago.[97]
In Europe, the teachings of Galen continued to dominate the academic community and his doctrines were adopted as the official canon of the Church. Andreas Vesalius questioned some of Galen's beliefs of the heart in De humani corporis fabrica (1543), but his magnum opus was interpreted as a challenge to the authorities and he was subjected to a number of attacks.[98] Michael Servetus wrote in Christianismi Restitutio (1553) that blood flows from one side of the heart to the other via the lungs.[98]
Modern
Animated heart
A breakthrough in understanding the flow of blood through the heart and body came with the publication of De Motu Cordis (1628) by the English physician William Harvey. Harvey's book completely describes the systemic circulation and the mechanical force of the heart, leading to an overhaul of the Galenic doctrines.[94] Otto Frank (1865–1944) was a German physiologist; among his many published works are detailed studies of this important heart relationship. Ernest Starling (1866–1927) was an important English physiologist who also studied the heart. Although they worked largely independently, their combined efforts and similar conclusions have been recognized in the name "Frank–Starling mechanism".[7]
Although Purkinje fibers and the bundle of His were discovered as early as the 19th century, their specific role in the electrical conduction system of the heart remained unknown until Sunao Tawara published his monograph, titled Das Reizleitungssystem des Säugetierherzens, in 1906. Tawara's discovery of the atrioventricular node prompted Arthur Keith and Martin Flack to look for similar structures in the heart, leading to their discovery of the sinoatrial node several months later. These structures form the anatomical basis of the electrocardiogram, whose inventor, Willem Einthoven, was awarded the Nobel Prize in Medicine or Physiology in 1924.[99]
The first heart transplant in a human ever performed was by James Hardy in 1964, using a chimpanzee heart, but the patient died within 2 hours.[100] The first human to human heart transplantation was performed in 1967 by the South African surgeon Christiaan Barnard at Groote Schuur Hospital in Cape Town.[101][102] This marked an important milestone in cardiac surgery, capturing the attention of both the medical profession and the world at large. However, long-term survival rates of patients were initially very low. Louis Washkansky, the first recipient of a donated heart, died 18 days after the operation while other patients did not survive for more than a few weeks.[103] The American surgeon Norman Shumway has been credited for his efforts to improve transplantation techniques, along with pioneers Richard Lower, Vladimir Demikhov and Adrian Kantrowitz. As of March 2000, more than 55,000 heart transplantations have been performed worldwide.[104] The first successful transplant of a heart from a genetically modified pig to a human in which the patient lived for a longer time, was performed January 7, 2022 in Baltimore by heart surgeon Bartley P. Griffith, recipient was David Bennett (57) this successfully extended his life until 8 March 2022 (1 month and 30 days).[105]
By the middle of the 20th century, heart disease had surpassed infectious disease as the leading cause of death in the United States, and it is currently the leading cause of deaths worldwide. Since 1948, the ongoing Framingham Heart Study has shed light on the effects of various influences on the heart, including diet, exercise, and common medications such as aspirin. Although the introduction of ACE inhibitors and beta blockers has improved the management of chronic heart failure, the disease continues to be an enormous medical and societal burden, with 30 to 40% of patients dying within a year of receiving the diagnosis.[106]
Society and culture
Further information: Sacred Heart, Heart symbol, and Blood § Cultural and religious beliefs
F34
jb (F34) "heart"
in hieroglyphs
Symbolism
Common heart symbol
Letter ღ of the Georgian script is often used as a "heart" symbol.
The seal script glyph for "heart" (Middle Chinese sim)
Elize Ryd making a heart sign at a concert in 2018
As one of the vital organs, the heart was long identified as the center of the entire body, the seat of life, or emotion, or reason, will, intellect, purpose or the mind.[107] The heart is an emblematic symbol in many religions, signifying "truth, conscience or moral courage in many religions—the temple or throne of God in Islamic and Judeo-Christian thought; the divine centre, or atman, and the third eye of transcendent wisdom in Hinduism; the diamond of purity and essence of the Buddha; the Taoist centre of understanding."[107]
In the Hebrew Bible, the word for heart, lev, is used in these meanings, as the seat of emotion, the mind, and referring to the anatomical organ. It is also connected in function and symbolism to the stomach.[108]
An important part of the concept of the soul in Ancient Egyptian religion was thought to be the heart, or ib. The ib or metaphysical heart was believed to be formed from one drop of blood from the child's mother's heart, taken at conception.[109] To ancient Egyptians, the heart was the seat of emotion, thought, will, and intention. This is evidenced by Egyptian expressions which incorporate the word ib, such as Awi-ib for "happy" (literally, "long of heart"), Xak-ib for "estranged" (literally, "truncated of heart").[110] In Egyptian religion, the heart was the key to the afterlife. It was conceived as surviving death in the nether world, where it gave evidence for, or against, its possessor. The heart was therefore not removed from the body during mummification, and was believed to be the center of intelligence and feeling, and needed in the afterlife.[111] It was thought that the heart was examined by Anubis and a variety of deities during the Weighing of the Heart ceremony. If the heart weighed more than the feather of Maat, which symbolized the ideal standard of behavior. If the scales balanced, it meant the heart's possessor had lived a just life and could enter the afterlife; if the heart was heavier, it would be devoured by the monster Ammit.[112]
The Chinese character for "heart", 心, derives from a comparatively realistic depiction of a heart (indicating the heart chambers) in seal script.[113] The Chinese word xīn also takes the metaphorical meanings of "mind", "intention", or "core", and is often translated as "heart-mind" as the ancient Chinese believed the heart was the center of human cognition.[114] In Chinese medicine, the heart is seen as the center of 神 shén "spirit, consciousness".[115] The heart is associated with the small intestine, tongue, governs the six organs and five viscera, and belongs to fire in the five elements.[116]
The Sanskrit word for heart is hṛd or hṛdaya, found in the oldest surviving Sanskrit text, the Rigveda. In Sanskrit, it may mean both the anatomical object and "mind" or "soul", representing the seat of emotion. Hrd may be a cognate of the word for heart in Greek, Latin, and English.[117][118]
Many classical philosophers and scientists, including Aristotle, considered the heart the seat of thought, reason, or emotion, often disregarding the brain as contributing to those functions.[119] The identification of the heart as the seat of emotions in particular is due to the Roman physician Galen, who also located the seat of the passions in the liver, and the seat of reason in the brain.[120]
The heart also played a role in the Aztec system of belief. The most common form of human sacrifice practiced by the Aztecs was heart-extraction. The Aztec believed that the heart (tona) was both the seat of the individual and a fragment of the Sun's heat (istli). To this day, the Nahua consider the Sun to be a heart-soul (tona-tiuh): "round, hot, pulsating".[121]
Indigenous leaders from Alaska to Australia came together in 2020 to deliver a message to the world that humanity needs to shift from the mind to the heart, and let our heart be in charge of what we do.[122] The message was made into a film, which highlighted that humanity must open their hearts to restore balance to the world.[123] Kumu Sabra Kauka, a Hawaiian studies educator and tradition bearer summed up the message of the film saying "Listen to your heart. Follow your path. May it be clear, and for the good of all."[122] The film was led by Illarion Merculieff from the Aleut (Unangan) tribe. Merculieff has written that Unangan Elders referred to the heart as a "source of wisdom", "a deeper portal of profound interconnectedness and awareness that exists between humans and all living things".[124][125]
In Catholicism, there has been a long tradition of veneration of the heart, stemming from worship of the wounds of Jesus Christ which gained prominence from the mid sixteenth century.[126] This tradition influenced the development of the medieval Christian devotion to the Sacred Heart of Jesus and the parallel veneration of the Immaculate Heart of Mary, made popular by John Eudes.[127] There are also many references to the heart in the Christian Bible, including "Blessed are the pure in heart, for they will see God",[128] "Above all else, guard your heart, for everything you do flows from it",[129] "For where your treasure is, there your heart will be also",[130] "For as a man thinks in his heart, so shall he be."[131]
The expression of a broken heart is a cross-cultural reference to grief for a lost one or to unfulfilled romantic love.
The notion of "Cupid's arrows" is ancient, due to Ovid, but while Ovid describes Cupid as wounding his victims with his arrows, it is not made explicit that it is the heart that is wounded. The familiar iconography of Cupid shooting little heart symbols is a Renaissance theme that became tied to Valentine's Day.[107]
In certain Trans-New Guinea languages, such as Foi and Momoona, the heart and seat of emotions are colexified, meaning they share the same word.[132]
Food
Animal hearts are widely consumed as food. As they are almost entirely muscle, they are high in protein. They are often included in dishes with other offal, for example in the pan-Ottoman kokoretsi.
Chicken hearts are considered to be giblets, and are often grilled on skewers; examples of this are Japanese hāto yakitori, Brazilian churrasco de coração, and Indonesian chicken heart satay.[133] They can also be pan-fried, as in Jerusalem mixed grill. In Egyptian cuisine, they can be used, finely chopped, as part of stuffing for chicken.[134] Many recipes combined them with other giblets, such as the Mexican pollo en menudencias[135] and the Russian ragu iz kurinyikh potrokhov.[136]
The hearts of beef, pork, and mutton can generally be interchanged in recipes. As heart is a hard-working muscle, it makes for "firm and rather dry" meat,[137] so is generally slow-cooked. Another way of dealing with toughness is to julienne the meat, as in Chinese stir-fried heart.[138]
Beef heart may be grilled or braised.[139] In the Peruvian anticuchos de corazón, barbecued beef hearts are grilled after being tenderized through long marination in a spice and vinegar mixture. An Australian recipe for "mock goose" is actually braised stuffed beef heart.[140]
Pig heart is stewed, poached, braised,[141] or made into sausage. The Balinese oret is a sort of blood sausage made with pig heart and blood. A French recipe for cœur de porc à l'orange is made of braised heart with an orange sauce.
Other animals
See also: Circulatory system
Vertebrates
The size of the heart varies among the different animal groups, with hearts in vertebrates ranging from those of the smallest mice (12 mg) to the blue whale (600 kg).[142] In vertebrates, the heart lies in the middle of the ventral part of the body, surrounded by a pericardium.[143] which in some fish may be connected to the peritoneum.[144]
The sinoatrial node is found in all amniotes but not in more primitive vertebrates. In these animals, the muscles of the heart are relatively continuous, and the sinus venosus coordinates the beat, which passes in a wave through the remaining chambers. Since the sinus venosus is incorporated into the right atrium in amniotes, it is likely homologous with the SA node. In teleosts, with their vestigial sinus venosus, the main centre of coordination is, instead, in the atrium. The rate of heartbeat varies enormously between different species, ranging from around 20 beats per minute in codfish to around 600 in hummingbirds[145] and up to 1200 bpm in the ruby-throated hummingbird.[146]
Double circulatory systems
Further information: Reptile § Circulation, and Snake § Internal organs
A cross section of a three-chambered adult amphibian heart. Note the single ventricle. The purple regions represent areas where mixing of oxygenated and de-oxygenated blood occurs.
Pulmonary vein
Left atrium
Right atrium
Ventricle
Conus arteriosus
Sinus venosus
Adult amphibians and most reptiles have a double circulatory system, meaning a circulatory system divided into arterial and venous parts. However, the heart itself is not completely separated into two sides. Instead, it is separated into three chambers—two atria and one ventricle. Blood returning from both the systemic circulation and the lungs is returned, and blood is pumped simultaneously into the systemic circulation and the lungs. The double system allows blood to circulate to and from the lungs which deliver oxygenated blood directly to the heart.[147]
In reptiles, other than snakes, the heart is usually situated around the middle of the thorax. In terrestrial and arboreal snakes it is usually located nearer to the head; in aquatic species the heart is more centrally located.[148] There is a heart with three chambers: two atria and one ventricle. The form and function of these hearts are different from mammalian hearts due to the fact that snakes have an elongated body, and thus are affected by different environmental factors. In particular, the snake's heart relative to the position in their body has been influenced greatly by gravity. Therefore, snakes that are larger in size tend to have a higher blood pressure due to gravitational change.[148] The ventricle is incompletely separated into two-halves by a wall (septum), with a considerable gap near the pulmonary artery and aortic openings. In most reptilian species, there appears to be little, if any, mixing between the bloodstreams, so the aorta receives, essentially, only oxygenated blood.[145][147] The exception to this rule is crocodiles, which have a four-chambered heart.[149]
In the heart of lungfish, the septum extends partway into the ventricle. This allows for some degree of separation between the de-oxygenated bloodstream destined for the lungs and the oxygenated stream that is delivered to the rest of the body. The absence of such a division in living amphibian species may be partly due to the amount of respiration that occurs through the skin; thus, the blood returned to the heart through the venae cavae is already partially oxygenated. As a result, there may be less need for a finer division between the two bloodstreams than in lungfish or other tetrapods. Nonetheless, in at least some species of amphibian, the spongy nature of the ventricle does seem to maintain more of a separation between the bloodstreams. Also, the original valves of the conus arteriosus have been replaced by a spiral valve that divides it into two parallel parts, thereby helping to keep the two bloodstreams separate.[145]
Full division
Archosaurs (crocodilians and birds) and mammals show complete separation of the heart into two pumps for a total of four heart chambers; it is thought that the four-chambered heart of archosaurs evolved independently from that of mammals. In crocodilians, there is a small opening, the foramen of Panizza, at the base of the arterial trunks and there is some degree of mixing between the blood in each side of the heart, during a dive underwater;[150][151] thus, only in birds and mammals are the two streams of blood—those to the pulmonary and systemic circulations—permanently kept entirely separate by a physical barrier.[145]
Fish
Main article: Fish anatomy § Heart
Blood flow through the fish heart: sinus venosus, atrium, ventricle, and outflow tract
The heart evolved no less than 380 million years ago in fish.[152] Fish have what is often described as a two-chambered heart,[153] consisting of one atrium to receive blood and one ventricle to pump it.[154] However, the fish heart has entry and exit compartments that may be called chambers, so it is also sometimes described as three-chambered[154] or four-chambered,[155] depending on what is counted as a chamber. The atrium and ventricle are sometimes considered "true chambers", while the others are considered "accessory chambers".[156]
Primitive fish have a four-chambered heart, but the chambers are arranged sequentially so that this primitive heart is quite unlike the four-chambered hearts of mammals and birds. The first chamber is the sinus venosus, which collects deoxygenated blood from the body through the hepatic and cardinal veins. From here, blood flows into the atrium and then to the powerful muscular ventricle where the main pumping action will take place. The fourth and final chamber is the conus arteriosus, which contains several valves and sends blood to the ventral aorta. The ventral aorta delivers blood to the gills where it is oxygenated and flows, through the dorsal aorta, into the rest of the body. (In tetrapods, the ventral aorta has divided in two; one half forms the ascending aorta, while the other forms the pulmonary artery).[145]
In the adult fish, the four chambers are not arranged in a straight row but instead form an S-shape, with the latter two chambers lying above the former two. This relatively simple pattern is found in cartilaginous fish and in the ray-finned fish. In teleosts, the conus arteriosus is very small and can more accurately be described as part of the aorta rather than of the heart proper. The conus arteriosus is not present in any amniotes, presumably having been absorbed into the ventricles over the course of evolution. Similarly, while the sinus venosus is present as a vestigial structure in some reptiles and birds, it is otherwise absorbed into the right atrium and is no longer distinguishable.[145]
Invertebrates
The tube-like heart (green) of the mosquito Anopheles gambiae extends horizontally across the body, interlinked with the diamond-shaped wing muscles (also green) and surrounded by pericardial cells (red). Blue depicts cell nuclei.
Basic arthropod body structure – heart shown in red
Arthropods and most mollusks have an open circulatory system. In this system, deoxygenated blood collects around the heart in cavities (sinuses). This blood slowly permeates the heart through many small one-way channels. The heart then pumps the blood into the hemocoel, a cavity between the organs. The heart in arthropods is typically a muscular tube that runs the length of the body, under the back and from the base of the head. Instead of blood the circulatory fluid is haemolymph which carries the most commonly used respiratory pigment, copper-based haemocyanin as the oxygen transporter. Haemoglobin is only used by a few arthropods.[157]
Schematic of cephalopod heart
In some other invertebrates such as earthworms, the circulatory system is not used to transport oxygen and so is much reduced, having no veins or arteries and consisting of two connected tubes. Oxygen travels by diffusion and there are five small muscular vessels that connect these vessels that contract at the front of the animals that can be thought of as "hearts".[157]
Squids and other cephalopods have two "gill hearts" also known as branchial hearts, and one "systemic heart".[158] The branchial hearts have two atria and one ventricle each, and pump to the gills, whereas the systemic heart pumps to the body.[159][160]
Only the chordates (including vertebrates) and the hemichordates have a central "heart", which is a vesicle formed from the thickening of the aorta and contracts to pump blood. This suggests a presence of it in the last common ancestor of these groups (may have been lost in the echinoderms).
Additional images
The human heart viewed from the front
The human heart viewed from the front
The human heart viewed from behind
The human heart viewed from behind
The coronary circulation
The coronary circulation
The human heart viewed from the front and from behind
The human heart viewed from the front and from behind
Frontal section of the human heart
Frontal section of the human heart
An anatomical specimen of the heart
An anatomical specimen of the heart
Heart illustration with circulatory system
Heart illustration with circulatory system
Animated heart 3D model rendered in computer
Animated heart 3D model rendered in computer
Notes
From the heart to the body
Arteries that contain deoxygenated blood, from the heart to the lungs
Supplying blood to the heart itself
From the body to the heart
Veins containing oxygenated blood from the lungs to the heart
Veins that drain blood from the cardiac tissue itself
Note the muscles do not cause the valves to open. The pressure difference between the blood in the atria and the ventricles does this.
Depolarisation of the ventricles occurs concurrently, but is not significant enough to be detected on an ECG.[86]
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Uhlén, Mathias; Fagerberg, Linn; Hallström, Björn M.; Lindskog, Cecilia; Oksvold, Per; Mardinoglu, Adil; Sivertsson, Åsa; Kampf, Caroline; Sjöstedt, Evelina (23 January 2015). "Tissue-based map of the human proteome". Science. 347 (6220): 1260419. doi:10.1126/science.1260419. ISSN 0036-8075. PMID 25613900. S2CID 802377.
Lindskog, Cecilia; Linné, Jerker; Fagerberg, Linn; Hallström, Björn M.; Sundberg, Carl Johan; Lindholm, Malene; Huss, Mikael; Kampf, Caroline; Choi, Howard (25 June 2015). "The h
he brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for special senses such as vision, hearing and olfaction. Being the most specialized organ, it is responsible for receiving information from the sensory nervous system, processing those information (thought, cognition, and intelligence) and the coordination of motor control (muscle activity and endocrine system).
While invertebrate brains arise from paired segmental ganglia (each of which is only responsible for the respective body segment) of the ventral nerve cord, vertebrate brains develop axially from the midline dorsal nerve cord as a vesicular enlargement at the rostral end of the neural tube, with centralized control over all body segments. All vertebrate brains can be embryonically divided into three parts: the forebrain (prosencephalon, subdivided into telencephalon and diencephalon), midbrain (mesencephalon) and hindbrain (rhombencephalon, subdivided into metencephalon and myelencephalon). The spinal cord, which directly interacts with somatic functions below the head, can be considered a caudal extension of the myelencephalon enclosed inside the vertebral column. Together, the brain and spinal cord constitute the central nervous system in all vertebrates.
In humans, the cerebral cortex contains approximately 14–16 billion neurons,[1] and the estimated number of neurons in the cerebellum is 55–70 billion.[2] Each neuron is connected by synapses to several thousand other neurons, typically communicating with one another via root-like protrusions called dendrites and long fiber-like extensions called axons, which are usually myelinated and carry trains of rapid micro-electric signal pulses called action potentials to target specific recipient cells in other areas of the brain or distant parts of the body. The prefrontal cortex, which controls executive functions, is particularly well developed in humans.
Physiologically, brains exert centralized control over a body's other organs. They act on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.
The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved.[3] Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from a digital computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways.
This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important that are covered in the human brain article are brain disease and the effects of brain damage.
Structure
a blob with a blue patch in the center, surrounded by a white area, surrounded by a thin strip of dark-colored material
Cross section of the olfactory bulb of a rat, stained in two different ways at the same time: one stain shows neuron cell bodies, the other shows receptors for the neurotransmitter GABA.
The shape and size of the brain varies greatly between species, and identifying common features is often difficult.[4] Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species.[5] Some aspects of brain structure are common to almost the entire range of animal species;[6] others distinguish "advanced" brains from more primitive ones, or distinguish vertebrates from invertebrates.[4]
The simplest way to gain information about brain anatomy is by visual inspection, but many more sophisticated techniques have been developed. Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the brain consists of areas of so-called grey matter, with a dark color, separated by areas of white matter, with a lighter color. Further information can be gained by staining slices of brain tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, and to trace the pattern of connections from one brain area to another.[7]
Cellular structure
drawing showing a neuron with a fiber emanating from it labeled "axon" and making contact with another cell. An inset shows an enlargement of the contact zone.
Neurons generate electrical signals that travel along their axons. When a pulse of electricity reaches a junction called a synapse, it causes a neurotransmitter chemical to be released, which binds to receptors on other cells and thereby alters their electrical activity.
The brains of all species are composed primarily of two broad classes of cells: neurons and glial cells. Glial cells (also known as glia or neuroglia) come in several types, and perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Neurons, however, are usually considered the most important cells in the brain.[8] The property that makes neurons unique is their ability to send signals to specific target cells over long distances.[8] They send these signals by means of an axon, which is a thin protoplasmic fiber that extends from the cell body and projects, usually with numerous branches, to other areas, sometimes nearby, sometimes in distant parts of the brain or body. The length of an axon can be extraordinary: for example, if a pyramidal cell (an excitatory neuron) of the cerebral cortex were magnified so that its cell body became the size of a human body, its axon, equally magnified, would become a cable a few centimeters in diameter, extending more than a kilometer.[9] These axons transmit signals in the form of electrochemical pulses called action potentials, which last less than a thousandth of a second and travel along the axon at speeds of 1–100 meters per second. Some neurons emit action potentials constantly, at rates of 10–100 per second, usually in irregular patterns; other neurons are quiet most of the time, but occasionally emit a burst of action potentials.[10]
Axons transmit signals to other neurons by means of specialized junctions called synapses. A single axon may make as many as several thousand synaptic connections with other cells.[8] When an action potential, traveling along an axon, arrives at a synapse, it causes a chemical called a neurotransmitter to be released. The neurotransmitter binds to receptor molecules in the membrane of the target cell.[8]
Synapses are the key functional elements of the brain.[11] The essential function of the brain is cell-to-cell communication, and synapses are the points at which communication occurs. The human brain has been estimated to contain approximately 100 trillion synapses;[12] even the brain of a fruit fly contains several million.[13] The functions of these synapses are very diverse: some are excitatory (exciting the target cell); others are inhibitory; others work by activating second messenger systems that change the internal chemistry of their target cells in complex ways.[11] A large number of synapses are dynamically modifiable; that is, they are capable of changing strength in a way that is controlled by the patterns of signals that pass through them. It is widely believed that activity-dependent modification of synapses is the brain's primary mechanism for learning and memory.[11]
Most of the space in the brain is taken up by axons, which are often bundled together in what are called nerve fiber tracts. A myelinated axon is wrapped in a fatty insulating sheath of myelin, which serves to greatly increase the speed of signal propagation. (There are also unmyelinated axons). Myelin is white, making parts of the brain filled exclusively with nerve fibers appear as light-colored white matter, in contrast to the darker-colored grey matter that marks areas with high densities of neuron cell bodies.[8]
Evolution
Main article: Evolution of the brain
Generic bilaterian nervous system
A rod-shaped body contains a digestive system running from the mouth at one end to the anus at the other. Alongside the digestive system is a nerve cord with a brain at the end, near to the mouth.
Nervous system of a generic bilaterian animal, in the form of a nerve cord with segmental enlargements, and a "brain" at the front
Except for a few primitive organisms such as sponges (which have no nervous system)[14] and cnidarians (which have a diffuse nervous system consisting of a nerve net),[14] all living multicellular animals are bilaterians, meaning animals with a bilaterally symmetric body plan (that is, left and right sides that are approximate mirror images of each other).[15] All bilaterians are thought to have descended from a common ancestor that appeared late in the Cryogenian period, 700–650 million years ago, and it has been hypothesized that this common ancestor had the shape of a simple tubeworm with a segmented body.[15] At a schematic level, that basic worm-shape continues to be reflected in the body and nervous system architecture of all modern bilaterians, including vertebrates.[16] The fundamental bilateral body form is a tube with a hollow gut cavity running from the mouth to the anus, and a nerve cord with an enlargement (a ganglion) for each body segment, with an especially large ganglion at the front, called the brain. The brain is small and simple in some species, such as nematode worms; in other species, such as vertebrates, it is a large and very complex organ.[4] Some types of worms, such as leeches, also have an enlarged ganglion at the back end of the nerve cord, known as a "tail brain".[17]
There are a few types of existing bilaterians that lack a recognizable brain, including echinoderms and tunicates. It has not been definitively established whether the existence of these brainless species indicates that the earliest bilaterians lacked a brain, or whether their ancestors evolved in a way that led to the disappearance of a previously existing brain structure.
Invertebrates
A fly resting on a reflective surface. A large, red eye faces the camera. The body appears transparent, apart from black pigment at the end of its abdomen.
Fruit flies (Drosophila) have been extensively studied to gain insight into the role of genes in brain development.
This category includes tardigrades, arthropods, molluscs, and numerous types of worms. The diversity of invertebrate body plans is matched by an equal diversity in brain structures.[18]
Two groups of invertebrates have notably complex brains: arthropods (insects, crustaceans, arachnids, and others), and cephalopods (octopuses, squids, and similar molluscs).[19] The brains of arthropods and cephalopods arise from twin parallel nerve cords that extend through the body of the animal. Arthropods have a central brain, the supraesophageal ganglion, with three divisions and large optical lobes behind each eye for visual processing.[19] Cephalopods such as the octopus and squid have the largest brains of any invertebrates.[20]
There are several invertebrate species whose brains have been studied intensively because they have properties that make them convenient for experimental work:
Fruit flies (Drosophila), because of the large array of techniques available for studying their genetics, have been a natural subject for studying the role of genes in brain development.[21] In spite of the large evolutionary distance between insects and mammals, many aspects of Drosophila neurogenetics have been shown to be relevant to humans. The first biological clock genes, for example, were identified by examining Drosophila mutants that showed disrupted daily activity cycles.[22] A search in the genomes of vertebrates revealed a set of analogous genes, which were found to play similar roles in the mouse biological clock—and therefore almost certainly in the human biological clock as well.[23] Studies done on Drosophila, also show that most neuropil regions of the brain are continuously reorganized throughout life in response to specific living conditions.[24]
The nematode worm Caenorhabditis elegans, like Drosophila, has been studied largely because of its importance in genetics.[25] In the early 1970s, Sydney Brenner chose it as a model organism for studying the way that genes control development. One of the advantages of working with this worm is that the body plan is very stereotyped: the nervous system of the hermaphrodite contains exactly 302 neurons, always in the same places, making identical synaptic connections in every worm.[26] Brenner's team sliced worms into thousands of ultrathin sections and photographed each one under an electron microscope, then visually matched fibers from section to section, to map out every neuron and synapse in the entire body.[27] The complete neuronal wiring diagram of C.elegans – its connectome was achieved.[28] Nothing approaching this level of detail is available for any other organism, and the information gained has enabled a multitude of studies that would otherwise have not been possible.[29]
The sea slug Aplysia californica was chosen by Nobel Prize-winning neurophysiologist Eric Kandel as a model for studying the cellular basis of learning and memory, because of the simplicity and accessibility of its nervous system, and it has been examined in hundreds of experiments.[30]
Vertebrates
A T-shaped object is made up of the cord at the bottom which feeds into a lower central mass. This is topped by a larger central mass with an arm extending from either side.
The brain of a shark
The first vertebrates appeared over 500 million years ago (Mya), during the Cambrian period, and may have resembled the modern hagfish in form.[31] Jawed fish appeared by 445 Mya, amphibians by 350 Mya, reptiles by 310 Mya and mammals by 200 Mya (approximately). Each species has an equally long evolutionary history, but the brains of modern hagfishes, lampreys, sharks, amphibians, reptiles, and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical components, but many are rudimentary in the hagfish, whereas in mammals the foremost part (the telencephalon) is greatly elaborated and expanded.[32]
Brains are most commonly compared in terms of their size. The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. As a rule, brain size increases with body size, but not in a simple linear proportion. In general, smaller animals tend to have larger brains, measured as a fraction of body size. For mammals, the relationship between brain volume and body mass essentially follows a power law with an exponent of about 0.75.[33] This formula describes the central tendency, but every family of mammals departs from it to some degree, in a way that reflects in part the complexity of their behavior. For example, primates have brains 5 to 10 times larger than the formula predicts. Predators tend to have larger brains than their prey, relative to body size.[34]
The nervous system is shown as a rod with protrusions along its length. The spinal cord at the bottom connects to the hindbrain which widens out before narrowing again. This is connected to the midbrain, which again bulges, and which finally connects to the forebrain which has two large protrusions.
The main subdivisions of the embryonic vertebrate brain (left), which later differentiate into structures of the adult brain (right)
All vertebrate brains share a common underlying form, which appears most clearly during early stages of embryonic development. In its earliest form, the brain appears as three swellings at the front end of the neural tube; these swellings eventually become the forebrain, midbrain, and hindbrain (the prosencephalon, mesencephalon, and rhombencephalon, respectively). At the earliest stages of brain development, the three areas are roughly equal in size. In many classes of vertebrates, such as fish and amphibians, the three parts remain similar in size in the adult, but in mammals the forebrain becomes much larger than the other parts, and the midbrain becomes very small.[8]
The brains of vertebrates are made of very soft tissue.[8] Living brain tissue is pinkish on the outside and mostly white on the inside, with subtle variations in color. Vertebrate brains are surrounded by a system of connective tissue membranes called meninges that separate the skull from the brain. Blood vessels enter the central nervous system through holes in the meningeal layers. The cells in the blood vessel walls are joined tightly to one another, forming the blood–brain barrier, which blocks the passage of many toxins and pathogens[35] (though at the same time blocking antibodies and some drugs, thereby presenting special challenges in treatment of diseases of the brain).[36]
Neuroanatomists usually divide the vertebrate brain into six main regions: the telencephalon (cerebral hemispheres), diencephalon (thalamus and hypothalamus), mesencephalon (midbrain), cerebellum, pons, and medulla oblongata. Each of these areas has a complex internal structure. Some parts, such as the cerebral cortex and the cerebellar cortex, consist of layers that are folded or convoluted to fit within the available space. Other parts, such as the thalamus and hypothalamus, consist of clusters of many small nuclei. Thousands of distinguishable areas can be identified within the vertebrate brain based on fine distinctions of neural structure, chemistry, and connectivity.[8]
Corresponding regions of human and shark brain are shown. The shark brain is splayed out, while the human brain is more compact. The shark brain starts with the medulla, which is surrounded by various structures, and ends with the telencephalon. The cross-section of the human brain shows the medulla at the bottom surrounded by the same structures, with the telencephalon thickly coating the top of the brain.
The main anatomical regions of the vertebrate brain, shown for shark and human. The same parts are present, but they differ greatly in size and shape.
Although the same basic components are present in all vertebrate brains, some branches of vertebrate evolution have led to substantial distortions of brain geometry, especially in the forebrain area. The brain of a shark shows the basic components in a straightforward way, but in teleost fishes (the great majority of existing fish species), the forebrain has become "everted", like a sock turned inside out. In birds, there are also major changes in forebrain structure.[37] These distortions can make it difficult to match brain components from one species with those of another species.[38]
Here is a list of some of the most important vertebrate brain components, along with a brief description of their functions as currently understood:
See also: List of regions in the human brain
The medulla, along with the spinal cord, contains many small nuclei involved in a wide variety of sensory and involuntary motor functions such as vomiting, heart rate and digestive processes.[8]
The pons lies in the brainstem directly above the medulla. Among other things, it contains nuclei that control often voluntary but simple acts such as sleep, respiration, swallowing, bladder function, equilibrium, eye movement, facial expressions, and posture.[39]
The hypothalamus is a small region at the base of the forebrain, whose complexity and importance belies its size. It is composed of numerous small nuclei, each with distinct connections and neurochemistry. The hypothalamus is engaged in additional involuntary or partially voluntary acts such as sleep and wake cycles, eating and drinking, and the release of some hormones.[40]
The thalamus is a collection of nuclei with diverse functions: some are involved in relaying information to and from the cerebral hemispheres, while others are involved in motivation. The subthalamic area (zona incerta) seems to contain action-generating systems for several types of "consummatory" behaviors such as eating, drinking, defecation, and copulation.[41]
The cerebellum modulates the outputs of other brain systems, whether motor-related or thought related, to make them certain and precise. Removal of the cerebellum does not prevent an animal from doing anything in particular, but it makes actions hesitant and clumsy. This precision is not built-in but learned by trial and error. The muscle coordination learned while riding a bicycle is an example of a type of neural plasticity that may take place largely within the cerebellum.[8] 10% of the brain's total volume consists of the cerebellum and 50% of all neurons are held within its structure.[42]
The optic tectum allows actions to be directed toward points in space, most commonly in response to visual input. In mammals, it is usually referred to as the superior colliculus, and its best-studied function is to direct eye movements. It also directs reaching movements and other object-directed actions. It receives strong visual inputs, but also inputs from other senses that are useful in directing actions, such as auditory input in owls and input from the thermosensitive pit organs in snakes. In some primitive fishes, such as lampreys, this region is the largest part of the brain.[43] The superior colliculus is part of the midbrain.
The pallium is a layer of grey matter that lies on the surface of the forebrain and is the most complex and most recent evolutionary development of the brain as an organ.[44] In reptiles and mammals, it is called the cerebral cortex. Multiple functions involve the pallium, including smell and spatial memory. In mammals, where it becomes so large as to dominate the brain, it takes over functions from many other brain areas. In many mammals, the cerebral cortex consists of folded bulges called gyri that create deep furrows or fissures called sulci. The folds increase the surface area of the cortex and therefore increase the amount of gray matter and the amount of information that can be stored and processed.[45]
The hippocampus, strictly speaking, is found only in mammals. However, the area it derives from, the medial pallium, has counterparts in all vertebrates. There is evidence that this part of the brain is involved in complex events such as spatial memory and navigation in fishes, birds, reptiles, and mammals.[46]
The basal ganglia are a group of interconnected structures in the forebrain. The primary function of the basal ganglia appears to be action selection: they send inhibitory signals to all parts of the brain that can generate motor behaviors, and in the right circumstances can release the inhibition, so that the action-generating systems are able to execute their actions. Reward and punishment exert their most important neural effects by altering connections within the basal ganglia.[47]
The olfactory bulb is a special structure that processes olfactory sensory signals and sends its output to the olfactory part of the pallium. It is a major brain component in many vertebrates, but is greatly reduced in humans and other primates (whose senses are dominated by information acquired by sight rather than smell).[48]
Reptiles
Anatomical comparison between the brain of a lizard (A and C) and the brain of a turkey (B and D). Abbreviations: Olf, olfactory lobes; Hmp, cerebral hemispheres; Pn, pineal gland ; Mb, optic lobes of the middle brain ; Cb, cerebellum; MO, medulla oblongata; ii, optic nerves; iv and vi, nerves for the muscles of the eye; Py, pituitary body.
Comparison of Vertebrate Brains: Mammalian, Reptilian, Amphibian, Teleost, and Ammocoetes. CB., cerebellum; PT., pituitary body; PN., pineal body; C. STR., corpus striatum; G.H.R., right ganglion habenulæ. I., olfactory; II., optic nerves.
Modern reptiles and mammals diverged from a common ancestor around 320 million years ago.[49] Interestingly, the number of extant reptiles far exceeds the number of mammalian species, with 11,733 recognized species of reptiles[50] compared to 5,884 extant mammals.[51] Along with the species diversity, reptiles have diverged in terms of external morphology, from limbless to tetrapod gliders to armored chelonians, reflecting adaptive radiation to a diverse array of environments.[52][53]
Morphological differences are reflected in the nervous system phenotype, such as: absence of lateral motor column neurons in snakes, which innervate limb muscles controlling limb movements; absence of motor neurons that innervate trunk muscles in tortoises; presence of innervation from the trigeminal nerve to pit organs responsible to infrared detection in snakes.[52] Variation in size, weight, and shape of the brain can be found within reptiles.[54] For instance, crocodilians have the largest brain volume to body weight proportion, followed by turtles, lizards, and snakes. Reptiles vary in the investment in different brain sections. Crocodilians have the largest telencephalon, while snakes have the smallest. Turtles have the largest diencephalon per body weight whereas crocodilians have the smallest. On the other hand, lizards have the largest mesencephalon.[54]
Yet their brains share several characteristics revealed by recent anatomical, molecular, and ontogenetic studies.[55][56][57] Vertebrates share the highest levels of similarities during embryological development, controlled by conserved transcription factors and signaling centers, including gene expression, morphological and cell type differentiation.[55][52][58] In fact, high levels of transcriptional factors can be found in all areas of the brain in reptiles and mammals, with shared neuronal clusters enlightening brain evolution.[56] Conserved transcription factors elucidate that evolution acted in different areas of the brain by either retaining similar morphology and function, or diversifying it.[55][56]
Anatomically, the reptilian brain has less subdivisions than the mammalian brain, however it has numerous conserved aspects including the organization of the spinal cord and cranial nerve, as well as elaborated brain pattern of organization.[59] Elaborated brains are characterized by migrated neuronal cell bodies away from the periventricular matrix, region of neuronal development, forming organized nuclear groups.[59] Aside from reptiles and mammals, other vertebrates with elaborated brains include hagfish, galeomorph sharks, skates, rays, teleosts, and birds.[59] Overall elaborated brains are subdivided in forebrain, midbrain, and hindbrain.
The hindbrain coordinates and integrates sensory and motor inputs and outputs responsible for, but not limited to, walking, swimming, or flying. It contains input and output axons interconnecting the spinal cord, midbrain and forebrain transmitting information from the external and internal environments.[59] The midbrain links sensory, motor, and integrative components received from the hindbrain, connecting it to the forebrain. The tectum, which includes the optic tectum and torus semicircularis, receives auditory, visual, and somatosensory inputs, forming integrated maps of the sensory and visual space around the animal.[59] The tegmentum receives incoming sensory information and forwards motor responses to and from the forebrain. The isthmus connects the hindbrain with midbrain. The forebrain region is particularly well developed, is further divided into diencephalon and telencephalon. Diencephalon is related to regulation of eye and body movement in response to visual stimuli, sensory information, circadian rhythms, olfactory input, and autonomic nervous system.Telencephalon is related to control of movements, neurotransmitters and neuromodulators responsible for integrating inputs and transmitting outputs are present, sensory systems, and cognitive functions.[59]
Birds
Main article: Avian brain
This section is an excerpt from Avian brain.[edit]
Brains of an emu, a kiwi, a barn owl, and a pigeon, with visual processing areas labelled
The avian brain is the central organ of the nervous system in birds. Birds possess large, complex brains, which process, integrate, and coordinate information received from the environment and make decisions on how to respond with the rest of the body. Like in all chordates, the avian brain is contained within the skull bones of the head.
The bird brain is divided into a number of sections, each with a different function. The cerebrum or telencephalon is divided into two hemispheres, and controls higher functions. The telencephalon is dominated by a large pallium, which corresponds to the mammalian cerebral cortex and is responsible for the cognitive functions of birds. The pallium is made up of several major structures: the hyperpallium, a dorsal bulge of the pallium found only in birds, as well as the nidopallium, mesopallium, and archipallium. The bird telencephalon nuclear structure, wherein neurons are distributed in three-dimensionally arranged clusters, with no large-scale separation of white matter and grey matter, though there exist layer-like and column-like connections. Structures in the pallium are associated with perception, learning, and cognition. Beneath the pallium are the two components of the subpallium, the striatum and pallidum. The subpallium connects different parts of the telencephalon and plays major roles in a number of critical behaviours. To the rear of the telencephalon are the thalamus, midbrain, and cerebellum. The hindbrain connects the rest of the brain to the spinal cord.
The size and structure of the avian brain enables prominent behaviours of birds such as flight and vocalization. Dedicated structures and pathways integrate the auditory and visual senses, strong in most species of birds, as well as the typically weaker olfactory and tactile senses. Social behaviour, widespread among birds, depends on the organisation and functions of the brain. Some birds exhibit strong abilities of cognition, enabled by the unique structure and physiology of the avian brain.
Mammals
The most obvious difference between the brains of mammals and other vertebrates is their size. On average, a mammal has a brain roughly twice as large as that of a bird of the same body size, and ten times as large as that of a reptile of the same body size.[60]
Size, however, is not the only difference: there are also substantial differences in shape. The hindbrain and midbrain of mammals are generally similar to those of other vertebrates, but dramatic differences appear in the forebrain, which is greatly enlarged and also altered in structure.[61] The cerebral cortex is the part of the brain that most strongly distinguishes mammals. In non-mammalian vertebrates, the surface of the cerebrum is lined with a comparatively simple three-layered structure called the pallium. In mammals, the pallium evolves into a complex six-layered structure called neocortex or isocortex.[62] Several areas at the edge of the neocortex, including the hippocampus and amygdala, are also much more extensively developed in mammals than in other vertebrates.[61]
The elaboration of the cerebral cortex carries with it changes to other brain areas. The superior colliculus, which plays a major role in visual control of behavior in most vertebrates, shrinks to a small size in mammals, and many of its functions are taken over by visual areas of the cerebral cortex.[60] The cerebellum of mammals contains a large portion (the neocerebellum) dedicated to supporting the cerebral cortex, which has no counterpart in other vertebrates.[63]
Primates
See also: Human brain
Encephalization Quotient
Species EQ[64]
Human 7.4–7.8
Common chimpanzee 2.2–2.5
Rhesus monkey 2.1
Bottlenose dolphin 4.14[65]
Elephant 1.13–2.36[66]
Dog 1.2
Horse 0.9
Rat 0.4
The brains of humans and other primates contain the same structures as the brains of other mammals, but are generally larger in proportion to body size.[67] The encephalization quotient (EQ) is used to compare brain sizes across species. It takes into account the nonlinearity of the brain-to-body relationship.[64] Humans have an average EQ in the 7-to-8 range, while most other primates have an EQ in the 2-to-3 range. Dolphins have values higher than those of primates other than humans,[65] but nearly all other mammals have EQ values that are substantially lower.
Most of the enlargement of the primate brain comes from a massive expansion of the cerebral cortex, especially the prefrontal cortex and the parts of the cortex involved in vision.[68] The visual processing network of primates includes at least 30 distinguishable brain areas, with a complex web of interconnections. It has been estimated that visual processing areas occupy more than half of the total surface of the primate neocortex.[69] The prefrontal cortex carries out functions that include planning, working memory, motivation, attention, and executive control. It takes up a much larger proportion of the brain for primates than for other species, and an especially large fraction of the human brain.[70]
Development
Main article: Neural development
Very simple drawing of the front end of a human embryo, showing each vesicle of the developing brain in a different color.
Brain of a human embryo in the sixth week of development
The brain develops in an intricately orchestrated sequence of stages.[71] It changes in shape from a simple swelling at the front of the nerve cord in the earliest embryonic stages, to a complex array of areas and connections. Neurons are created in special zones that contain stem cells, and then migrate through the tissue to reach their ultimate locations. Once neurons have positioned themselves, their axons sprout and navigate through the brain, branching and extending as they go, until the tips reach their targets and form synaptic connections. In a number of parts of the nervous system, neurons and synapses are produced in excessive numbers during the early stages, and then the unneeded ones are pruned away.[71]
For vertebrates, the early stages of neural development are similar across all species.[71] As the embryo transforms from a round blob of cells into a wormlike structure, a narrow strip of ectoderm running along the midline of the back is induced to become the neural plate, the precursor of the nervous system. The neural plate folds inward to form the neural groove, and then the lips that line the groove merge to enclose the neural tube, a hollow cord of cells with a fluid-filled ventricle at the center. At the front end, the ventricles and cord swell to form three vesicles that are the precursors of the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain). At the next stage, the forebrain splits into two vesicles called the telencephalon (which will contain the cerebral cortex, basal ganglia, and related structures) and the diencephalon (which will contain the thalamus and hypothalamus). At about the same time, the hindbrain splits into the metencephalon (which will contain the cerebellum and pons) and the myelencephalon (which will contain the medulla oblongata). Each of these areas contains proliferative zones where neurons and glial cells are generated; the resulting cells then migrate, sometimes for long distances, to their final positions.[71]
Once a neuron is in place, it extends dendrites and an axon into the area around it. Axons, because they commonly extend a great distance from the cell body and need to reach specific targets, grow in a particularly complex way. The tip of a growing axon consists of a blob of protoplasm called a growth cone, studded with chemical receptors. These receptors sense the local environment, causing the growth cone to be attracted or repelled by various cellular elements, and thus to be pulled in a particular direction at each point along its path. The result of this pathfinding process is that the growth cone navigates through the brain until it reaches its destination area, where other chemical cues cause it to begin generating synapses. Considering the entire brain, thousands of genes create products that influence axonal pathfinding.[71]
The synaptic network that finally emerges is only partly determined by genes, though. In many parts of the brain, axons initially "overgrow", and then are "pruned" by mechanisms that depend on neural activity.[71] In the projection from the eye to the midbrain, for example, the structure in the adult contains a very precise mapping, connecting each point on the surface of the retina to a corresponding point in a midbrain layer. In the first stages of development, each axon from the retina is guided to the right general vicinity in the midbrain by chemical cues, but then branches very profusely and makes initial contact with a wide swath of midbrain neurons. The retina, before birth, contains special mechanisms that cause it to generate waves of activity that originate spontaneously at a random point and then propagate slowly across the retinal layer. These waves are useful because they cause neighboring neurons to be active at the same time; that is, they produce a neural activity pattern that contains information about the spatial arrangement of the neurons. This information is exploited in the midbrain by a mechanism that causes synapses to weaken, and eventually vanish, if activity in an axon is not followed by activity of the target cell. The result of this sophisticated process is a gradual tuning and tightening of the map, leaving it finally in its precise adult form.[72]
Similar things happen in other brain areas: an initial synaptic matrix is generated as a result of genetically determined chemical guidance, but then gradually refined by activity-dependent mechanisms, partly driven by internal dynamics, partly by external sensory inputs. In some cases, as with the retina-midbrain system, activity patterns depend on mechanisms that operate only in the developing brain, and apparently exist solely to guide development.[72]
In humans and many other mammals, new neurons are created mainly before birth, and the infant brain contains substantially more neurons than the adult brain.[71] There are, however, a few areas where new neurons continue to be generated throughout life. The two areas for which adult neurogenesis is well established are the olfactory bulb, which is involved in the sense of smell, and the dentate gyrus of the hippocampus, where there is evidence that the new neurons play a role in storing newly acquired memories. With these exceptions, however, the set of neurons that is present in early childhood is the set that is present for life. Glial cells are different: as with most types of cells in the body, they are generated throughout the lifespan.[73]
There has long been debate about whether the qualities of mind, personality, and intelligence can be attributed to heredity or to upbringing.[74] Although many details remain to be settled, neuroscience shows that both factors are important. Genes determine both the general form of the brain and how it reacts to experience, but experience is required to refine the matrix of synaptic connections, resulting in greatly increased complexity. The presence or absence of experience is critical at key periods of development.[75] Additionally, the quantity and quality of experience are important. For example, animals raised in enriched environments demonstrate thick cerebral cortices, indicating a high density of synaptic connections, compared to animals with restricted levels of stimulation.[76]
Physiology
The functions of the brain depend on the ability of neurons to transmit electrochemical signals to other cells, and their ability to respond appropriately to electrochemical signals received from other cells. The electrical properties of neurons are controlled by a wide variety of biochemical and metabolic processes, most notably the interactions between neurotransmitters and receptors that take place at synapses.[8]
Neurotransmitters and receptors
Neurotransmitters are chemicals that are released at synapses when the local membrane is depolarised and Ca2+ enters into the cell, typically when an action potential arrives at the synapse – neurotransmitters attach themselves to receptor molecules on the membrane of the synapse's target cell (or cells), and thereby alter the electrical or chemical properties of the receptor molecules. With few exceptions, each neuron in the brain releases the same chemical neurotransmitter, or combination of neurotransmitters, at all the synaptic connections it makes with other neurons; this rule is known as Dale's principle.[8] Thus, a neuron can be characterized by the neurotransmitters that it releases. The great majority of psychoactive drugs exert their effects by altering specific neurotransmitter systems. This applies to drugs such as cannabinoids, nicotine, heroin, cocaine, alcohol, fluoxetine, chlorpromazine, and many others.[77]
The two neurotransmitters that are most widely found in the vertebrate brain are glutamate, which almost always exerts excitatory effects on target neurons, and gamma-aminobutyric acid (GABA), which is almost always inhibitory. Neurons using these transmitters can be found in nearly every part of the brain.[78] Because of their ubiquity, drugs that act on glutamate or GABA tend to have broad and powerful effects. Some general anesthetics act by reducing the effects of glutamate; most tranquilizers exert their sedative effects by enhancing the effects of GABA.[79]
There are dozens of other chemical neurotransmitters that are used in more limited areas of the brain, often areas dedicated to a particular function. Serotonin, for example—the primary target of many antidepressant drugs and many dietary aids—comes exclusively from a small brainstem area called the raphe nuclei.[80] Norepinephrine, which is involved in arousal, comes exclusively from a nearby small area called the locus coeruleus.[81] Other neurotransmitters such as acetylcholine and dopamine have multiple sources in the brain but are not as ubiquitously distributed as glutamate and GABA.[82]
Electrical activity
Graph showing 16 voltage traces going across the page from left to right, each showing a different signal. At the middle of the page all of the traces abruptly begin to show sharp jerky spikes, which continue to the end of the plot.
Brain electrical activity recorded from a human patient during an epileptic seizure
As a side effect of the electrochemical processes used by neurons for signaling, brain tissue generates electric fields when it is active. When large numbers of neurons show synchronized activity, the electric fields that they generate can be large enough to detect outside the skull, using electroencephalography (EEG)[83] or magnetoencephalography (MEG). EEG recordings, along with recordings made from electrodes implanted inside the brains of animals such as rats, show that the brain of a living animal is constantly active, even during sleep.[84] Each part of the brain shows a mixture of rhythmic and nonrhythmic activity, which may vary according to behavioral state. In mammals, the cerebral cortex tends to show large slow delta waves during sleep, faster alpha waves when the animal is awake but inattentive, and chaotic-looking irregular activity when the animal is actively engaged in a task, called beta and gamma waves. During an epileptic seizure, the brain's inhibitory control mechanisms fail to function and electrical activity rises to pathological levels, producing EEG traces that show large wave and spike patterns not seen in a healthy brain. Relating these population-level patterns to the computational functions of individual neurons is a major focus of current research in neurophysiology.[84]
Metabolism
All vertebrates have a blood–brain barrier that allows metabolism inside the brain to operate differently from metabolism in other parts of the body. The neurovascular unit regulates cerebral blood flow so that activated neurons can be supplied with energy. Glial cells play a major role in brain metabolism by controlling the chemical composition of the fluid that surrounds neurons, including levels of ions and nutrients.[85]
Brain tissue consumes a large amount of energy in proportion to its volume, so large brains place severe metabolic demands on animals. The need to limit body weight in order, for example, to fly, has apparently led to selection for a reduction of brain size in some species, such as bats.[86] Most of the brain's energy consumption goes into sustaining the electric charge (membrane potential) of neurons.[85] Most vertebrate species devote between 2% and 8% of basal metabolism to the brain. In primates, however, the percentage is much higher—in humans it rises to 20–25%.[87] The energy consumption of the brain does not vary greatly over time, but active regions of the cerebral cortex consume somewhat more energy than inactive regions; this forms the basis for the functional brain imaging methods of PET, fMRI,[88] and NIRS.[89] The brain typically gets most of its energy from oxygen-dependent metabolism of glucose (i.e., blood sugar),[85] but ketones provide a major alternative source, together with contributions from medium chain fatty acids (caprylic and heptanoic acids),[90][91] lactate,[92] acetate,[93] and possibly amino acids.[94]
Function
Model of a neural circuit in the cerebellum, as proposed by James S. Albus
Information from the sense organs is collected in the brain. There it is used to determine what actions the organism is to take. The brain processes the raw data to extract information about the structure of the environment. Next it combines the processed information with information about the current needs of the animal and with memory of past circumstances. Finally, on the basis of the results, it generates motor response patterns. These signal-processing tasks require intricate interplay between a variety of functional subsystems.[95]
The function of the brain is to provide coherent control over the actions of an animal. A centralized brain allows groups of muscles to be co-activated in complex patterns; it also allows stimuli impinging on one part of the body to evoke responses in other parts, and it can prevent different parts of the body from acting at cross-purposes to each other.[95]
Perception
Drawing showing the ear, inner ear, and brain areas involved in hearing. A series of light blue arrows shows the flow of signals through the system.
Diagram of signal processing in the auditory system
The human brain is provided with information about light, sound, the chemical composition of the atmosphere, temperature, the position of the body in space (proprioception), the chemical composition of the bloodstream, and more. In other animals additional senses are present, such as the infrared heat-sense of snakes, the magnetic field sense of some birds, or the electric field sense mainly seen in aquatic animals.
Each sensory system begins with specialized receptor cells,[8] such as photoreceptor cells in the retina of the eye, or vibration-sensitive hair cells in the cochlea of the ear. The axons of sensory receptor cells travel into the spinal cord or brain, where they transmit their signals to a first-order sensory nucleus dedicated to one specific sensory modality. This primary sensory nucleus sends information to higher-order sensory areas that are dedicated to the same modality. Eventually, via a way-station in the thalamus, the signals are sent to the cerebral cortex, where they are processed to extract the relevant features, and integrated with signals coming from other sensory systems.[8]
Motor control
Motor systems are areas of the brain that are involved in initiating body movements, that is, in activating muscles. Except for the muscles that control the eye, which are driven by nuclei in the midbrain, all the voluntary muscles in the body are directly innervated by motor neurons in the spinal cord and hindbrain.[8] Spinal motor neurons are controlled both by neural circuits intrinsic to the spinal cord, and by inputs that descend from the brain. The intrinsic spinal circuits implement many reflex responses, and contain pattern generators for rhythmic movements such as walking or swimming. The descending connections from the brain allow for more sophisticated control.[8]
The brain contains several motor areas that project directly to the spinal cord. At the lowest level are motor areas in the medulla and pons, which control stereotyped movements such as walking, breathing, or swallowing. At a higher level are areas in the midbrain, such as the red nucleus, which is responsible for coordinating movements of the arms and legs. At a higher level yet is the primary motor cortex, a strip of tissue located at the posterior edge of the frontal lobe. The primary motor cortex sends projections to the subcortical motor areas, but also sends a massive projection directly to the spinal cord, through the pyramidal tract. This direct corticospinal projection allows for precise voluntary control of the fine details of movements. Other motor-related brain areas exert secondary effects by projecting to the primary motor areas. Among the most important secondary areas are the premotor cortex, supplementary motor area, basal ganglia, and cerebellum.[8] In addition to all of the above, the brain and spinal cord contain extensive circuitry to control the autonomic nervous system which controls the movement of the smooth muscle of the body.[8]
Major areas involved in controlling movement
Area Location Function
Ventral horn Spinal cord Contains motor neurons that directly activate muscles[96]
Oculomotor nuclei Midbrain Contains motor neurons that directly activate the eye muscles[97]
Cerebellum Hindbrain Calibrates precision and timing of movements[8]
Basal ganglia Forebrain Action selection on the basis of motivation[98]
Motor cortex Frontal lobe Direct cortical activation of spinal motor circuits[99]
Premotor cortex Frontal lobe Groups elementary movements into coordinated patterns[8]
Supplementary motor area Frontal lobe Sequences movements into temporal patterns[100]
Prefrontal cortex Frontal lobe Planning and other executive functions[101]
Sleep
Main article: Sleep
See also: Circadian rhythm and arousal
Many animals alternate between sleeping and waking in a daily cycle. Arousal and alertness are also modulated on a finer time scale by a network of brain areas.[8] A key component of the sleep system is the suprachiasmatic nucleus (SCN), a tiny part of the hypothalamus located directly above the point at which the optic nerves from the two eyes cross. The SCN contains the body's central biological clock. Neurons there show activity levels that rise and fall with a period of about 24 hours, circadian rhythms: these activity fluctuations are driven by rhythmic changes in expression of a set of "clock genes". The SCN continues to keep time even if it is excised from the brain and placed in a dish of warm nutrient solution, but it ordinarily receives input from the optic nerves, through the retinohypothalamic tract (RHT), that allows daily light-dark cycles to calibrate the clock.[102]
The SCN projects to a set of areas in the hypothalamus, brainstem, and midbrain that are involved in implementing sleep-wake cycles. An important component of the system is the reticular formation, a group of neuron-clusters scattered diffusely through the core of the lower brain. Reticular neurons send signals to the thalamus, which in turn sends activity-level-controlling signals to every part of the cortex. Damage to the reticular formation can produce a permanent state of coma.[8]
Sleep involves great changes in brain activity.[8] Until the 1950s it was generally believed that the brain essentially shuts off during sleep,[103] but this is now known to be far from true; activity continues, but patterns become very different. There are two types of sleep: REM sleep (with dreaming) and NREM (non-REM, usually without dreaming) sleep, which repeat in slightly varying patterns throughout a sleep episode. Three broad types of distinct brain activity patterns can be measured: REM, light NREM and deep NREM. During deep NREM sleep, also called slow wave sleep, activity in the cortex takes the form of large synchronized waves, whereas in the waking state it is noisy and desynchronized. Levels of the neurotransmitters norepinephrine and serotonin drop during slow wave sleep, and fall almost to zero during REM sleep; levels of acetylcholine show the reverse pattern.[8]
Homeostasis
Cross-section of a human head, showing location of the hypothalamus
For any animal, survival requires maintaining a variety of parameters of bodily state within a limited range of variation: these include temperature, water content, salt concentration in the bloodstream, blood glucose levels, blood oxygen level, and others.[104] The ability of an animal to regulate the internal environment of its body—the milieu intérieur, as the pioneering physiologist Claude Bernard called it—is known as homeostasis (Greek for "standing still").[105] Maintaining homeostasis is a crucial function of the brain. The basic principle that underlies homeostasis is negative feedback: any time a parameter diverges from its set-point, sensors generate an error signal that evokes a response that causes the parameter to shift back toward its optimum value.[104] (This principle is widely used in engineering, for example in the control of temperature using a thermostat.)
In vertebrates, the part of the brain that plays the greatest role is the hypothalamus, a small region at the base of the forebrain whose size does not reflect its complexity or the importance of its function.[104] The hypothalamus is a collection of small nuclei, most of which are involved in basic biological functions. Some of these functions relate to arousal or to social interactions such as sexuality, aggression, or maternal behaviors; but many of them relate to homeostasis. Several hypothalamic nuclei receive input from sensors located in the lining of blood vessels, conveying information about temperature, sodium level, glucose level, blood oxygen level, and other parameters. These hypothalamic nuclei send output signals to motor areas that can generate actions to rectify deficiencies. Some of the outputs also go to the pituitary gland, a tiny gland attached to the brain directly underneath the hypothalamus. The pituitary gland secretes hormones into the bloodstream, where they circulate throughout the body and induce changes in cellular activity.[106]
Motivation
Components of the basal ganglia, shown in two cross-sections of the human brain. Blue: caudate nucleus and putamen. Green: globus pallidus. Red: subthalamic nucleus. Black: substantia nigra.
The individual animals need to express survival-promoting behaviors, such as seeking food, water, shelter, and a mate.[107] The motivational system in the brain monitors the current state of satisfaction of these goals, and activates behaviors to meet any needs that arise. The motivational system works largely by a reward–punishment mechanism. When a particular behavior is followed by favorable consequences, the reward mechanism in the brain is activated, which induces structural changes inside the brain that cause the same behavior to be repeated later, whenever a similar situation arises. Conversely, when a behavior is followed by unfavorable consequences, the brain's punishment mechanism is activated, inducing structural changes that cause the behavior to be suppressed when similar situations arise in the future.[108]
Most organisms studied to date use a reward–punishment mechanism: for instance, worms and insects can alter their behavior to seek food sources or to avoid dangers.[109] In vertebrates, the reward-punishment system is implemented by a specific set of brain structures, at the heart of which lie the basal ganglia, a set of interconnected areas at the base of the forebrain.[47] The basal ganglia are the central site at which decisions are made: the basal ganglia exert a sustained inhibitory control over most of the motor systems in the brain; when this inhibition is released, a motor system is permitted to execute the action it is programmed to carry out. Rewards and punishments function by altering the relationship between the inputs that the basal ganglia receive and the decision-signals that are emitted. The reward mechanism is better understood than the punishment mechanism, because its role in drug abuse has caused it to be studied very intensively. Research has shown that the neurotransmitter dopamine plays a central role: addictive drugs such as cocaine, amphetamine, and nicotine either cause dopamine levels to rise or cause the effects of dopamine inside the brain to be enhanced.[110]
Learning and memory
Almost all animals are capable of modifying their behavior as a result of experience—even the most primitive types of worms. Because behavior is driven by brain activity, changes in behavior must somehow correspond to changes inside the brain. Already in the late 19th century theorists like Santiago Ramón y Cajal argued that the most plausible explanation is that learning and memory are expressed as changes in the synaptic connections between neurons.[111] Until 1970, however, experimental evidence to support the synaptic plasticity hypothesis was lacking. In 1971 Tim Bliss and Terje Lømo published a paper on a phenomenon now called long-term potentiation: the paper showed clear evidence of activity-induced synaptic changes that lasted for at least several days.[112] Since then technical advances have made these sorts of experiments much easier to carry out, and thousands of studies have been made that have clarified the mechanism of synaptic change, and uncovered other types of activity-driven synaptic change in a variety of brain areas, including the cerebral cortex, hippocampus, basal ganglia, and cerebellum.[113] Brain-derived neurotrophic factor (BDNF) and physical activity appear to play a beneficial role in the process.[114]
Neuroscientists currently distinguish several types of learning and memory that are implemented by the brain in distinct ways:
Working memory is the ability of the brain to maintain a temporary representation of information about the task that an animal is currently engaged in. This sort of dynamic memory is thought to be mediated by the formation of cell assemblies—groups of activated neurons that maintain their activity by constantly stimulating one another.[115]
Episodic memory is the ability to remember the details of specific events. This sort of memory can last for a lifetime. Much evidence implicates the hippocampus in playing a crucial role: people with severe damage to the hippocampus sometimes show amnesia, that is, inability to form new long-lasting episodic memories.[116]
Semantic memory is the ability to learn facts and relationships. This sort of memory is probably stored largely in the cerebral cortex, mediated by changes in connections between cells that represent specific types of information.[117]
Instrumental learning is the ability for rewards and punishments to modify behavior. It is implemented by a network of brain areas centered on the basal ganglia.[118]
Motor learning is the ability to refine patterns of body movement by practicing, or more generally by repetition. A number of brain areas are involved, including the premotor cortex, basal ganglia, and especially the cerebellum, which functions as a large memory bank for microadjustments of the parameters of movement.[119]
Research
Main article: Neuroscience
"Brain research" redirects here. For the scientific journal, see Brain Research.
The Human Brain Project is a large scientific research project, starting in 2013, which aims to simulate the complete human brain.
The field of neuroscience encompasses all approaches that seek to understand the brain and the rest of the nervous system.[8] Psychology seeks to understand mind and behavior, and neurology is the medical discipline that diagnoses and treats diseases of the nervous system. The brain is also the most important organ studied in psychiatry, the branch of medicine that works to study, prevent, and treat mental disorders.[120] Cognitive science seeks to unify neuroscience and psychology with other fields that concern themselves with the brain, such as computer science (artificial intelligence and similar fields) and philosophy.[121]
The oldest method of studying the brain is anatomical, and until the middle of the 20th century, much of the progress in neuroscience came from the development of better cell stains and better microscopes. Neuroanatomists study the large-scale structure of the brain as well as the microscopic structure of neurons and their components, especially synapses. Among other tools, they employ a plethora of stains that reveal neural structure, chemistry, and connectivity. In recent years, the development of immunostaining techniques has allowed investigation of neurons that express specific sets of genes. Also, functional neuroanatomy uses medical imaging techniques to correlate variations in human brain structure with differences in cognition or behavior.[122]
Neurophysiologists study the chemical, pharmacological, and electrical properties of the brain: their primary tools are drugs and recording devices. Thousands of experimentally developed drugs affect the nervous system, some in highly specific ways. Recordings of brain activity can be made using electrodes, either glued to the scalp as in EEG studies, or implanted inside the brains of animals for extracellular recordings, which can detect action potentials generated by individual neurons.[123] Because the brain does not contain pain receptors, it is possible using these techniques to record brain activity from animals that are awake and behaving without causing distress. The same techniques have occasionally been used to study brain activity in human patients with intractable epilepsy, in cases where there was a medical necessity to implant electrodes to localize the brain area responsible for epileptic seizures.[124] Functional imaging techniques such as fMRI are also used to study brain activity; these techniques have mainly been used with human subjects, because they require a conscious subject to remain motionless for long periods of time, but they have the great advantage of being noninvasive.[125]
Drawing showing a monkey in a restraint chair, a computer monitor, a rototic arm, and three pieces of computer equipment, with arrows between them to show the flow of information.
Design of an experiment in which brain activity from a monkey was used to control a robotic arm[126]
Another approach to brain function is to examine the consequences of damage to specific brain areas. Even though it is protected by the skull and meninges, surrounded by cerebrospinal fluid, and isolated from the bloodstream by the blood–brain barrier, the delicate nature of the brain makes it vulnerable to numerous diseases and several types of damage. In humans, the effects of strokes and other types of brain damage have been a key source of information about brain function. Because there is no ability to experimentally control the nature of the damage, however, this information is often difficult to interpret. In animal studies, most commonly involving rats, it is possible to use electrodes or locally injected chemicals to produce precise patterns of damage and then examine the consequences for behavior.[127]
Computational neuroscience encompasses two approaches: first, the use of computers to study the brain; second, the study of how brains perform computation. On one hand, it is possible to write a computer program to simulate the operation of a group of neurons by making use of systems of equations that describe their electrochemical activity; such simulations are known as biologically realistic neural networks. On the other hand, it is possible to study algorithms for neural computation by simulating, or mathematically analyzing, the operations of simplified "units" that have some of the properties of neurons but abstract out much of their biological complexity. The computational functions of the brain are studied both by computer scientists and neuroscientists.[128]
Computational neurogenetic modeling is concerned with the study and development of dynamic neuronal models for modeling brain functions with respect to genes and dynamic interactions between genes.
Recent years have seen increasing applications of genetic and genomic techniques to the study of the brain [129] and a focus on the roles of neurotrophic factors and physical activity in neuroplasticity.[114] The most common subjects are mice, because of the availability of technical tools. It is now possible with relative ease to "knock out" or mutate a wide variety of genes, and then examine the effects on brain function. More sophisticated approaches are also being used: for example, using Cre-Lox recombination it is possible to activate or deactivate genes in specific parts of the brain, at specific times.[129]
Recent years have also seen rapid advances in single-cell sequencing technologies, and these have been used to leverage the cellular heterogeneity of the brain as a means of better understanding the roles of distinct cell types in disease and biology (as well as how genomic variants influence individual cell types). In 2024, investigators studied a large integrated dataset of almost 3 million nuclei from the human prefrontal cortext from 388 individuals.[130] In doing so, they annotated 28 cell types to evaluate expression and chromatin variation across gene families and drug targets. They identified about half a million cell type–specific regulatory elements and about 1.5 million single-cell expression quantitative trait loci (ie, genomic variants with strong statistical associations with changes in gene expression within specific cell types), which were then used to build cell-type regulatory networks (the study also describes cell-to-cell communication networks). These networks were found to manifest cellular changes in aging and neuropsychiatric disorders. As part of the same same investigation, a machine learning model was designed to accurately impute single-cell expression (this model prioritized ~250 disease-risk genes and drug targets with associated cell types).
History
See also: History of neuroscience
Illustration by René Descartes of how the brain implements a reflex response
The oldest brain to have been discovered was in Armenia in the Areni-1 cave complex. The brain, estimated to be over 5,000 years old, was found in the skull of a 12 to 14-year-old girl. Although the brains were shriveled, they were well preserved due to the climate found inside the cave.[131]
Early philosophers were divided as to whether the seat of the soul lies in the brain or heart. Aristotle favored the heart, and thought that the function of the brain was merely to cool the blood. Democritus, the inventor of the atomic theory of matter, argued for a three-part soul, with intellect in the head, emotion in the heart, and lust near the liver.[132] The unknown author of On the Sacred Disease, a medical treatise in the Hippocratic Corpus, came down unequivocally in favor of the brain, writing:
Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations. ... And by the same organ we become mad and delirious, and fears and terrors assail us, some by night, and some by day, and dreams and untimely wanderings, and cares that are not suitable, and ignorance of present circumstances, desuetude, and unskillfulness. All these things we endure from the brain, when it is not healthy...
— On the Sacred Disease, attributed to Hippocrates[133]
Andreas Vesalius' Fabrica, published in 1543, showing the base of the human brain, including optic chiasma, cerebellum, olfactory bulbs, etc.
The Roman physician Galen also argued for the importance of the brain, and theorized in some depth about how it might work. Galen traced out the anatomical relationships among brain, nerves, and muscles, demonstrating that all muscles in the body are connected to the brain through a branching network of nerves. He postulated that nerves activate muscles mechanically by carrying a mysterious substance he called pneumata psychikon, usually translated as "animal spirits".[132] Galen's ideas were widely known during the Middle Ages, but not much further progress came until the Renaissance, when detailed anatomical study resumed, combined with the theoretical speculations of René Descartes and those who followed him. Descartes, like Galen, thought of the nervous system in hydraulic terms. He believed that the highest cognitive functions are carried out by a non-physical res cogitans, but that the majority of behaviors of humans, and all behaviors of animals, could be explained mechanistically.[132]
The first real progress toward a modern understanding of nervous function, though, came from the investigations of Luigi Galvani (1737–1798), who discovered that a shock of static electricity applied to an exposed nerve of a dead frog could cause its leg to contract. Since that time, each major advance in understanding has followed more or less directly from the development of a new technique of investigation. Until the early years of the 20th century, the most important advances were derived from new methods for staining cells.[134] Particularly critical was the invention of the Golgi stain, which (when correctly used) stains only a small fraction of neurons, but stains them in their entirety, including cell body, dendrites, and axon. Without such a stain, brain tissue under a microscope appears as an impenetrable tangle of protoplasmic fibers, in which it is impossible to determine any structure. In the hands of Camillo Golgi, and especially of the Spanish neuroanatomist Santiago Ramón y Cajal, the new stain revealed hundreds of distinct types of neurons, each with its own unique dendritic structure and pattern of connectivity.[135]
A drawing on yellowing paper with an archiving stamp in the corner. A spidery tree branch structure connects to the top of a mass. A few narrow processes follow away from the bottom of the mass.
Drawing by Santiago Ramón y Cajal of two types of Golgi-stained neurons from the cerebellum of a pigeon
In the first half of the 20th century, advances in electronics enabled investigation of the electrical properties of nerve cells, culminating in work by Alan Hodgkin, Andrew Huxley, and others on the biophysics of the action potential, and the work of Bernard Katz and others on the electrochemistry of the synapse.[136] These studies complemented the anatomical picture with a conception of the brain as a dynamic entity. Reflecting the new understanding, in 1942 Charles Sherrington visualized the workings of the brain waking from sleep:
The great topmost sheet of the mass, that where hardly a light had twinkled or moved, becomes now a sparkling field of rhythmic flashing points with trains of traveling sparks hurrying hither and thither. The brain is waking and with it the mind is returning. It is as if the Milky Way entered upon some cosmic dance. Swiftly the head mass becomes an enchanted loom where millions of flashing shuttles weave a dissolving pattern, always a meaningful pattern though never an abiding one; a shifting harmony of subpatterns.
— Sherrington, 1942, Man on his Nature[137]
The invention of electronic computers in the 1940s, along with the development of mathematical information theory, led to a realization that brains can potentially be understood as information processing systems. This concept formed the basis of the field of cybernetics, and eventually gave rise to the field now known as computational neuroscience.[138] The earliest attempts at cybernetics were somewhat crude in that they treated the brain as essentially a digital computer in disguise, as for example in John von Neumann's 1958 book, The Computer and the Brain.[139] Over the years, though, accumulating information about the electrical responses of brain cells recorded from behaving animals has steadily moved theoretical concepts in the direction of increasing realism.[138]
One of the most influential early contributions was a 1959 paper titled What the frog's eye tells the frog's brain: the paper examined the visual responses of neurons in the retina and optic tectum of frogs, and came to the conclusion that some neurons in the tectum of the frog are wired to combine elementary responses in a way that makes them function as "bug perceivers".[140] A few years later David Hubel and Torsten Wiesel discovered cells in the primary visual cortex of monkeys that become active when sharp edges move across specific points in the field of view—a discovery for which they won a Nobel Prize.[141] Follow-up studies in higher-order visual areas found cells that detect binocular disparity, color, movement, and aspects of shape, with areas located at increasing distances from the primary visual cortex showing increasingly complex responses.[142] Other investigations of brain areas unrelated to vision have revealed cells with a wide variety of response correlates, some related to memory, some to abstract types of cognition such as space.[143]
Theorists have worked to understand these response patterns by constructing mathematical models of neurons and neural networks, which can be simulated using computers.[138] Some useful models are abstract, focusing on the conceptual structure of neural algorithms rather than the details of how they are implemented in the brain; other models attempt to incorporate data about the biophysical properties of real neurons.[144] No model on any level is yet considered to be a fully valid description of brain function, though. The essential difficulty is that sophisticated computation by neural networks requires distributed processing in which hundreds or thousands of neurons work cooperatively—current methods of brain activity recording are only capable of isolating action potentials from a few dozen neurons at a time.[145]
Furthermore, even single neurons appear to be complex and capable of performing computations.[146] So, brain models that do not reflect this are too abstract to be representative of brain operation; models that do try to capture this are very computationally expensive and arguably intractable with present computational resources. However, the Human Brain Project is trying to build a realistic, detailed computational model of the entire human brain. The wisdom of this approach has been publicly contested, with high-profile scientists on both sides of the argument.
In the second half of the 20th century, developments in chemistry, electron microscopy, genetics, computer science, functional brain imaging, and other fields progressively opened new windows into brain structure and function. In the United States, the 1990s were officially designated as the "Decade of the Brain" to commemorate advances made in brain research, and to promote funding for such research.[147]
In the 21st century, these trends have continued, and several new approaches have come into prominence, including multielectrode recording, which allows the activity of many brain cells to be recorded all at the same time;[148] genetic engineering, which allows molecular components of the brain to be altered experimentally;[129] genomics, which allows variations in brain structure to be correlated with variations in DNA properties and neuroimaging.[149]
Society and culture
As food
Main article: Brain as food
Gulai otak, beef brain curry from Indonesia
Animal brains are used as food in numerous cuisines.
In rituals
Some archaeological evidence suggests that the mourning rituals of European Neanderthals also involved the consumption of the brain.[150]
The Fore people of Papua New Guinea are known to eat human brains. In funerary rituals, those close to the dead would eat the brain of the deceased to create a sense of immortality. A prion disease called kuru has been traced to this.[151]
See also
Philosophy portal
Brain–computer interface
Central nervous system disease
List of neuroscience databases
Neurological disorder
Optogenetics
Outline of neuroscience
Aging brain
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External links
Wikiquote has quotations related to Brain.
Wikimedia Commons has media related to Brain.
Wikisource has the text of the 1911 Encyclopædia Britannica article "Brain".
The Brain from Top to Bottom, at McGill University
"The Brain", BBC Radio 4 discussion with Vivian Nutton, Jonathan Sawday & Marina Wallace (In Our Time, May 8, 2008)
Our Quest to Understand the Brain – with Matthew Cobb Royal Institution lecture. Archived at Ghostarchive.
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A brain tumor occurs when abnormal cells form within the brain.[2] There are two main types of tumors: malignant (cancerous) tumors and benign (non-cancerous) tumors.[2] These can be further classified as primary tumors, which start within the brain, and secondary tumors, which most commonly have spread from tumors located outside the brain, known as brain metastasis tumors.[1] All types of brain tumors may produce symptoms that vary depending on the size of the tumor and the part of the brain that is involved.[2] Where symptoms exist, they may include headaches, seizures, problems with vision, vomiting and mental changes.[1][2][7] Other symptoms may include difficulty walking, speaking, with sensations, or unconsciousness.[1][3]
The cause of most brain tumors is unknown, though up to 4% of brain cancers may be caused by CT scan radiation.[2][8] Uncommon risk factors include exposure to vinyl chloride, Epstein–Barr virus, ionizing radiation, and inherited syndromes such as neurofibromatosis, tuberous sclerosis, and von Hippel-Lindau Disease.[1][2][3] Studies on mobile phone exposure have not shown a clear risk.[3] The most common types of primary tumors in adults are meningiomas (usually benign) and astrocytomas such as glioblastomas.[1] In children, the most common type is a malignant medulloblastoma.[3] Diagnosis is usually by medical examination along with computed tomography (CT) or magnetic resonance imaging (MRI).[2] The result is then often confirmed by a biopsy. Based on the findings, the tumors are divided into different grades of severity.[1]
Treatment may include some combination of surgery, radiation therapy and chemotherapy.[1] If seizures occur, anticonvulsant medication may be needed.[1] Dexamethasone and furosemide are medications that may be used to decrease swelling around the tumor.[1] Some tumors grow gradually, requiring only monitoring and possibly needing no further intervention.[1] Treatments that use a person's immune system are being studied.[2] Outcomes for malignant tumors vary considerably depending on the type of tumor and how far it has spread at diagnosis.[3] Although benign tumors only grow in one area, they may still be life-threatening depending on their size and location.[9] Malignant glioblastomas usually have very poor outcomes, while benign meningiomas usually have good outcomes.[3] The average five-year survival rate for all (malignant) brain cancers in the United States is 33%.[4]
Secondary, or metastatic, brain tumors are about four times as common as primary brain tumors,[2][10] with about half of metastases coming from lung cancer.[2] Primary brain tumors occur in around 250,000 people a year globally, and make up less than 2% of cancers.[3] In children younger than 15, brain tumors are second only to acute lymphoblastic leukemia as the most common form of cancer.[11] In NSW Australia in 2005, the average lifetime economic cost of a case of brain cancer was AU$1.9 million, the greatest of any type of cancer.[12]
Signs and symptoms
The signs and symptoms of brain tumors are broad. People may experience symptoms regardless of whether the tumor is benign (not cancerous) or cancerous.[13] Primary and secondary brain tumors present with similar symptoms, depending on the location, size, and rate of growth of the tumor.[14] For example, larger tumors in the frontal lobe can cause changes in the ability to think. However, a smaller tumor in an area such as Wernicke's area (small area responsible for language comprehension) can result in a greater loss of function.[15]
Headaches
Headaches as a result of raised intracranial pressure can be an early symptom of brain cancer.[16] However, isolated headache without other symptoms is rare, and other symptoms including visual abnormalities may occur before headaches become common.[16] Certain warning signs for headache exist which make the headache more likely to be associated with brain cancer.[16] These are defined as "abnormal neurological examination, headache worsened by Valsalva maneuver, headache causing awakening from sleep, new headache in the older population, progressively worsening headache, atypical headache features, or patients who do not fulfill the strict definition of migraine".[16] Other associated signs are headaches that are worse in the morning or that subside after vomiting.[17]
Location-specific symptoms
The main areas of the brain and limbic system
The brain is divided into lobes and each lobe or area has its own function.[18][19] A tumor in any of these lobes may affect the area's performance. The symptoms experienced are often linked to the location of the tumor, but each person may experience something different.[20]
Frontal lobe: Tumors may contribute to poor reasoning, inappropriate social behavior, personality changes, poor planning, lower inhibition, and decreased production of speech (Broca's area).[20]
Temporal lobe: Tumors in this lobe may contribute to poor memory, loss of hearing, and difficulty in language comprehension (Wernicke's area is located in this lobe).[19]
Parietal lobe: Tumors here may result in poor interpretation of languages, difficulty with speaking, writing, drawing, naming, and recognizing, and poor spatial and visual perception.[21]
Occipital lobe: Damage to this lobe may result in poor vision or loss of vision.[22]
Cerebellum: Tumors in this area may cause poor balance, muscle movement, and posture.[23]
Brain stem: Tumors on the brainstem can cause seizures, endocrine problems, respiratory changes, visual changes, headaches and partial paralysis.[23]
Behavior changes
A person's personality may be altered due to the tumor-damaging lobes of the brain. Since the frontal, temporal, and parietal lobes[14] control inhibition, emotions, mood, judgement, reasoning, and behavior, a tumor in those regions can cause inappropriate social behavior,[24] temper tantrums,[24] laughing at things which merit no laughter,[24] and even psychological symptoms such as depression and anxiety.[20] More research is needed into the effectiveness and safety of medication for depression in people with brain tumors.[25]
Personality changes can have damaging effects such as unemployment, unstable relationships, and a lack of control.[18]
Cause
The best known cause of brain cancers is ionizing radiation.[8][26] Approximately 4% of brain cancers in the general population are caused by CT scan radiation.[8] For brain cancers that follow a CT scan at lags of 2 years or more, it has been estimated that 40% are attributable to CT scan radiation.[8] The relationship between ionizing radiation and brain cancers can be best explained by radiation carcinogenesis, and traditional models of oncogenesis. The stochastic effects of ionizing radiation demonstrate a dose-response relationship to the probability of occurrence, but no dose-response relationship to severity of disease. The majority of radiation-induced brain cancers are caused by ionizing radiation from medical sources such as CT scans.
Mutations and deletions of tumor suppressor genes, such as P53, are thought to be the cause of some forms of brain tumor.[27] Inherited conditions, such as Von Hippel–Lindau disease, tuberous sclerosis, multiple endocrine neoplasia, and neurofibromatosis type 2 carry a high risk for the development of brain tumors.[1][28][29] People with celiac disease have a slightly increased risk of developing brain tumors.[30] Smoking has been suggested to increase the risk but evidence remains unclear.[31]
Although studies have not shown any link between cell phone or mobile phone radiation and the occurrence of brain tumors,[32] the World Health Organization has classified mobile phone radiation on the IARC scale into Group 2B – possibly carcinogenic.[33] The claim that cell phone usage may cause brain cancer is likely based on epidemiological studies which observed a slight increase in glioma risk among heavy users of wireless phones. When those studies were conducted, GSM (2G) phones were in use. Modern, third-generation (3G) phones emit, on average, about 1% of the energy emitted by those GSM (2G) phones, and therefore the finding of an association between cell phone usage and increased risk of brain cancer is not based upon current phone usage.[3]
Pathophysiology
Meninges
The meninges lie between the skull and brain matter. Tumors originating from the meninges are meningiomas.
Human brains are surrounded by a system of connective tissue membranes called meninges that separate the brain from the skull. This three-layered covering is composed of (from the outside in) the dura mater, arachnoid mater, and pia mater. The arachnoid and pia are physically connected and thus often considered as a single layer, the leptomeninges. Between the arachnoid mater and the pia mater is the subarachnoid space which contains cerebrospinal fluid (CSF). This fluid circulates in the narrow spaces between cells and through the cavities in the brain called ventricles, to support and protect the brain tissue. Blood vessels enter the central nervous system through the perivascular space above the pia mater. The cells in the blood vessel walls are joined tightly, forming the blood–brain barrier which protects the brain from toxins that might enter through the blood.[34]
Tumors of the meninges are meningiomas and are often benign. Though not technically a tumor of brain tissue, they are often considered brain tumors since they protrude into the space where the brain is, causing symptoms. Since they are usually slow-growing tumors, meningiomas can be quite large by the time symptoms appear.[35]
Brain matter
The brains of humans and other vertebrates are composed of very soft tissue and have a gelatin-like texture. Living brain tissue has a pink tint in color on the outside (gray matter), and nearly complete white on the inside (white matter), with subtle variations in color. The three largest divisions of the brain are:
Cerebral cortex
Brainstem
Cerebellum[34]
These areas are composed of two broad classes of cells: neurons and glia. These two types are equally numerous in the brain as a whole, although glial cells outnumber neurons roughly 4 to 1 in the cerebral cortex. Glia come in several types, which perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development.[36] Primary tumors of the glial cells are called gliomas and often are malignant by the time they are diagnosed.[37]
The thalamus and hypothalamus are major divisions of the diencephalon, with the pituitary gland and pineal gland attached at the bottom; tumors of the pituitary[38] and pineal gland[citation needed] are often benign.
The brainstem lies between the large cerebral cortex and the spinal cord. It is divided into the midbrain, pons, and medulla oblongata.[34]
Spinal cord
The spinal cord is considered a part of the central nervous system.[39] It is made up of the same cells as the brain: neurons and glial cells.[34]
Diagnosis
A posterior fossa tumor leading to mass effect and midline shift
Although there is no specific or singular symptom or sign, the presence of a combination of symptoms and the lack of corresponding indications of other causes can be an indicator for investigation towards the possibility of a brain tumor. Brain tumors have similar characteristics and obstacles when it comes to diagnosis and therapy with tumors located elsewhere in the body. However, they create specific issues that follow closely to the properties of the organ they are in.[40]
The diagnosis will often start by taking a medical history noting medical antecedents, and current symptoms. Clinical and laboratory investigations will serve to exclude infections as the cause of the symptoms. Examinations in this stage may include the eyes, otolaryngological (or ENT) and electrophysiological exams. The use of electroencephalography (EEG) often plays a role in the diagnosis of brain tumors.[41]
Brain tumors, when compared to tumors in other areas of the body, pose a challenge for diagnosis. Commonly, radioactive tracers are uptaken in large volumes in tumors due to the high activity of tumor cells, allowing for radioactive imaging of the tumor. However, most of the brain is separated from the blood by the blood–brain barrier (BBB), a membrane that exerts a strict control over what substances are allowed to pass into the brain. Therefore, many tracers that may reach tumors in other areas of the body easily would be unable to reach brain tumors until there was a disruption of the BBB by the tumor. Disruption of the BBB is well imaged via MRI or CT scan, and is therefore regarded as the main diagnostic indicator for malignant gliomas, meningiomas, and brain metastases.[40]
Swelling or obstruction of the passage of cerebrospinal fluid (CSF) from the brain may cause (early) signs of increased intracranial pressure which translates clinically into headaches, vomiting, or an altered state of consciousness, and in children changes to the diameter of the skull and bulging of the fontanelles. More complex symptoms such as endocrine dysfunctions should alarm doctors not to exclude brain tumors.[citation needed]
A bilateral temporal visual field defect (due to compression of the optic chiasm) or dilation of the pupil, and the occurrence of either slowly evolving or the sudden onset of focal neurologic symptoms, such as cognitive and behavioral impairment (including impaired judgment, memory loss, lack of recognition, spatial orientation disorders), personality or emotional changes, hemiparesis, hypoesthesia, aphasia, ataxia, visual field impairment, impaired sense of smell, impaired hearing, facial paralysis, double vision, or more severe symptoms such as tremors, paralysis on one side of the body hemiplegia, or (epileptic) seizures in a patient with a negative history for epilepsy, should raise the possibility of a brain tumor.[citation needed]
Imaging
CT scan of a brain tumor, with its diameters marked as an X. There is hypoattenuating (dark) peritumoral edema in the surrounding white matter, with a "finger-like" spread.
Medical imaging plays a central role in the diagnosis of brain tumors. Early imaging methods – invasive and sometimes dangerous – such as pneumoencephalography and cerebral angiography have been abandoned in favor of non-invasive, high-resolution techniques, especially magnetic resonance imaging (MRI) and computed tomography (CT) scans,[39] though MRI is typically the reference standard used.[42] Neoplasms will often show as differently colored masses (also referred to as processes) in CT or MRI results.[citation needed]
Benign brain tumors often show up as hypodense (darker than brain tissue) mass lesions on CT scans. On MRI, they appear either hypodense or isointense (same intensity as brain tissue) on T1-weighted scans, or hyperintense (brighter than brain tissue) on T2-weighted MRI, although the appearance is variable.
Contrast agent uptake, sometimes in characteristic patterns, can be demonstrated on either CT or MRI scans in most malignant primary and metastatic brain tumors.
Pressure areas where the brain tissue has been compressed by a tumor also appear hyperintense on T2-weighted scans and might indicate the presence of a diffuse neoplasm due to an unclear outline. Swelling around the tumor known as peritumoral edema can also show a similar result. This is because these tumors disrupt the normal functioning of the BBB and lead to an increase in its permeability.
More recently, advancements have been made to increase the utility of MRI in providing physiological data that can help to inform diagnosis and prognosis. MRI itself is sufficient in identifying the brain tumor's location and morphology, but other types of MRI may be used on top of that, such as MRA, MRS, pMRI, fMRI, and DWI. These imaging techniques help doctors and surgeons to diagnose the type of tumor, plan for surgery, and to assess treatment and radiation/chemotherapy. Treatment with radiation and chemotherapy can lead to treatment induced changes in the brain, visible on conventional imaging and which can be difficult to differentiate from tumor recurrence.[43]
Different Types of MRI Scans
Magnetic Resonance Angiography (MRA) – looks at the blood vessels in the brain. In the diagnosis of brain tumor, MRAs are typically carried out before surgery to help surgeons get a better understanding of the tumor vasculature. For example, a study was done where surgeons were able to separate benign brain tumors from malignant ones by analyzing the shapes of the blood vessels that were extracted from MRA.[44] Although not required, some MRA may inject contrast agent, gadolinium, into the patient to get an enhanced image
Magnetic Resonance Spectroscopy (MRS) – measures the metabolic changes or chemical changes inside the tumor. The most common MRS is proton spectroscopy with its frequency measured in parts per million (ppm). Gliomas or malignant brain tumors have different spectra from normal brain tissue in that they have greater choline levels and lower N-acetyl aspartate (NAA) signals.[45] Using MRS in brain tumor diagnosis can help doctors identify the type of tumor and its aggressiveness. For example, benign brain tumors or meningioma have increased alanine levels. It can also help to distinguish brain tumors from scar tissues or dead tissues caused by previous radiation treatment, which does not have increased choline levels[46] that brain tumors have, and from tumor-mimicking lesions such as abscesses or infarcts.
Perfusion Magnetic Resonance Imaging (pMRI) – assess the blood volume and blood flow of different parts of the brain and brain tumors. pMRI requires the injection of contrast agent, usually gadopentetate dimeglumine (Gd-DTPA) into the veins in order to enhance the contrast. pMRI provides a cerebral blood volume map that shows the tumor vascularity and angiogenesis. Brain tumors would require a larger blood supply and thus, would show a high cerebral blood volume on the pMRI map. The vascular morphology and degree of angiogenesis from pMRI help to determine the grade and malignancy of brain tumors. For brain tumor diagnosis, pMRI is useful in determining the best site to perform biopsy and to help reduce sampling error. pMRI is also valuable for after treatment to determine if the abnormal area is a remaining tumor or a scar tissue. For patients that are undergoing anti-angiogenesis cancer therapy, pMRI can give the doctors a better sense of efficacy of the treatment by monitoring tumor cerebral blood volume.[47]
Functional MRI (fMRI) – measures blood flow changes in active parts of the brain while the patient is performing tasks and provides specific locations of the brain that are responsible for certain functions. Before performing a brain tumor surgery on patients, neurosurgeons would use fMRI to avoid damage to structures of the brain that correspond with important brain functions while resecting the tumor at the same time. Preoperative fMRI is important because it is often difficult to distinguish the anatomy near the tumor as it distorts its surrounding regions. Neurosurgeons would use fMRI to plan whether to perform a resection where tumor is surgically removed as much as possible, a biopsy where they take a surgical sampling amount to provide a diagnosis, or to not undergo surgery at all. For example, a neurosurgeon may be opposed to resecting a tumor near the motor cortex as that would affect the patient's movements. Without preoperative fMRI, the neurosurgeon would have to perform an awake-craniotomy where the patient would have to interact during open surgery to see if tumor removal would affect important brain functions.[48]
Diffusion Weighted Imaging (DWI) – a form of MRI that measures random Brownian motion of water molecules along a magnetic field gradient. For brain tumor diagnosis, measurement of apparent diffusion coefficient (ADC) in brain tumors allow doctors to categorize tumor type. Most brain tumors have higher ADC than normal brain tissues and doctors can match the observed ADC of the patient's brain tumor with a list of accepted ADC to identify tumor type. DWI is also useful for treatment and therapy purposes where changes in diffusion can be analyzed in response to drug, radiation, or gene therapy. Successful response results in apoptosis and increase in diffusion while failed treatment results in unchanged diffusion values.[49]
Other Types of Imaging Techniques
Computed Tomography (CT) Scan – uses x-rays to take pictures from different angles and computer processing to combine the pictures into a 3D image. A CT scan usually serves as an alternative to MRI in cases where the patient cannot have an MRI due to claustrophobia or pacemaker. Compared to MRI, a CT scan shows a more detailed image of the bone structures near the tumor and can be used to measure the tumor's size.[50] Like an MRI, a contrast dye may also be injected into the veins or ingested by mouth before a CT scan to better outline any tumors that may be present. CT scans use contrast materials that are iodine-based and barium sulfate compounds. The downside of using CT scans as opposed to MRI is that some brain tumors do not show up well on CT scans because some intra-axial masses are faint and resemble normal brain tissue. In some scenarios, brain tumors in CT scans may be mistaken for infarction, infection, and demyelination. To suspect that an intra-axial mass is a brain tumor instead of other possibilities, there must be unexplained calcifications in the brain, preservation of the cortex, and disproportionate mass effect.[51]
CT Angiography (CTA) – provides information about the blood vessels in the brain using X-rays. A contrast agent is always required to be injected into the patient in the CT scanner. CTA serves as an alternative to MRA.
Positron Emission Tomography (PET) Scan – uses radioactive substances, with the most common one being a sugar known as FDG, while more specific tracers for glioma are emerging.[52] This injected substance is taken up by cells that are actively dividing. Tumor cells are more active in dividing so they would absorb more of the radioactive substance. After injection, a scanner would be used to create an image of the radioactive areas in the brain. PET scans are used more often for high-grade tumors than for low-grade tumors. It is useful after treatment to help doctors determine if the abnormal area on an MRI image is a remaining tumor or a scar tissue. Scar tissues will not show up on PET scans while tumors would.[50]
However, these techniques cannot alone diagnose high- versus low-grade gliomas, and thus the definitive diagnosis of brain tumor should only be confirmed by histological examination of tumor tissue samples obtained either by means of brain biopsy or open surgery. The histological examination is essential for determining the appropriate treatment and the correct prognosis. This examination, performed by a pathologist, typically has three stages: interoperative examination of fresh tissue, preliminary microscopic examination of prepared tissues, and follow-up examination of prepared tissues after immunohistochemical staining or genetic analysis.[citation needed]
Pathology
Micrograph of an oligodendroglioma, a type of brain cancer. Brain biopsy. H&E stain.
Tumors have characteristics that allow the determination of malignancy and how they will evolve, and determining these characteristics will allow the medical team to determine the management plan.[citation needed]
Anaplasia or dedifferentiation: loss of differentiation of cells and of their orientation to one another and blood vessels, a characteristic of anaplastic tumor tissue. Anaplastic cells have lost total control of their normal functions and many have deteriorated cell structures. Anaplastic cells often have abnormally high nuclear-to-cytoplasmic ratios, and many are multinucleated. Additionally, the nucleus of anaplastic cells is usually unnaturally shaped or oversized. Cells can become anaplastic in two ways: neoplastic tumor cells can dedifferentiate to become anaplasias (the dedifferentiation causes the cells to lose all of their normal structure/function), or cancer stem cells can increase their capacity to multiply (i.e., uncontrollable growth due to failure of differentiation).[citation needed]
Atypia: an indication of abnormality of a cell (which may be indicative of malignancy). Significance of the abnormality is highly dependent on context.[53]
Neoplasia: the (uncontrolled) division of cells. As such, neoplasia is not problematic but its consequences are: the uncontrolled division of cells means that the mass of a neoplasm increases in size, and in a confined space such as the intracranial cavity this quickly becomes problematic because the mass invades the space of the brain pushing it aside, leading to compression of the brain tissue and increased intracranial pressure and destruction of brain parenchyma. Increased intracranial pressure (ICP) may be attributable to the direct mass effect of the tumor, increased blood volume, or increased cerebrospinal fluid (CSF) volume, which may, in turn, have secondary symptoms.[citation needed]
Necrosis: the (premature) death of cells, caused by external factors such as infection, toxin or trauma. Necrotic cells send the wrong chemical signals which prevent phagocytes from disposing of the dead cells, leading to a buildup of dead tissue, cell debris and toxins at or near the site of the necrotic cells[54]
Arterial and venous hypoxia, or the deprivation of adequate oxygen supply to certain areas of the brain, occurs when a tumor makes use of nearby blood vessels for its supply of blood and the neoplasm enters into competition for nutrients with the surrounding brain tissue.[55] More generally a neoplasm may cause release of metabolic end products (e.g., free radicals, altered electrolytes, neurotransmitters), and release and recruitment of cellular mediators (e.g., cytokines) that disrupt normal parenchymal function.[citation needed][56]
Classification
Tumors can be benign or malignant, can occur in different parts of the brain, and may be classified as primary or secondary. A primary tumor is one that has started in the brain, as opposed to a metastatic tumor, which is one that has spread to the brain from another area of the body.[57] The incidence of metastatic tumors is approximately four times greater than primary tumors.[10] Tumors may or may not be symptomatic: some tumors are discovered because the patient has symptoms, others show up incidentally on an imaging scan, or at an autopsy.[citation needed]
Grading of the tumors of the central nervous system commonly occurs on a 4-point scale (I-IV) created by the World Health Organization in 1993. Grade I tumors are the least severe and commonly associated with long-term survival, with severity and prognosis worsening as the grade increases. Low-grade tumors are often benign, while higher grades are aggressively malignant and/or metastatic. Other grading scales do exist, many based upon the same criteria as the WHO scale and graded from I-IV.[58]
Primary
Meningioma of the middle third of the sagittal sinus with large hyperostosis
The most common primary brain tumors are:[59]
Gliomas[60] (50.4%)
Meningiomas[60] (20.8%)
Pituitary adenomas[60] (15%)
Nerve sheath tumors (10%)
These common tumors can also be organized according to tissue of origin as shown below:[61]
Tissue of origin
Children Adults
Astrocytes Pilocytic Astrocytoma (PCA) Glioblastoma
Oligodendrocytes Oligodendroglioma
Ependyma Ependymoma
Neurons Medulloblastoma
Meninges Meningioma
Secondary
Secondary tumors of the brain are metastatic and have invaded the brain from cancers originating in other organs. This means that a cancerous neoplasm has developed in another organ elsewhere in the body and that cancer cells have leaked from that primary tumor and then entered the lymphatic system and blood vessels. They then circulate through the bloodstream, and are deposited in the brain. There, these cells continue growing and dividing, becoming another invasive neoplasm of primary cancer's tissue. Secondary tumors of the brain are very common in the terminal phases of patients with an incurable metastasized cancer; the most common types of cancers that bring about secondary tumors of the brain are lung cancer, breast cancer, malignant melanoma, kidney cancer, and colon cancer (in decreasing order of frequency).[citation needed]
Secondary brain tumors are more common than primary ones; in the United States, there are about 170,000 new cases every year. Secondary brain tumors are the most common cause of tumors in the intracranial cavity. The skull bone structure can also be subject to a neoplasm that by its very nature reduces the volume of the intracranial cavity, and can damage the brain.[62]
By behavior
Brain tumors or intracranial neoplasms can be cancerous (malignant) or non-cancerous (benign). However, the definitions of malignant or benign neoplasms differ from those commonly used in other types of cancerous or non-cancerous neoplasms in the body. In cancers elsewhere in the body, three malignant properties differentiate benign tumors from malignant forms of cancer: benign tumors are self-limited and do not invade or metastasize. Characteristics of malignant tumors include:[63]
uncontrolled mitosis (growth by division beyond the normal limits)
anaplasia: the cells in the neoplasm have an obviously different form (in size and shape). Anaplastic cells display marked pleomorphism. The cell nuclei are characteristically extremely hyperchromatic (darkly stained) and enlarged; the nucleus might have the same size as the cytoplasm of the cell (nuclear-cytoplasmic ratio may approach 1:1, instead of the normal 1:4 or 1:6 ratio). Giant cells – considerably larger than their neighbors – may form and possess either one enormous nucleus or several nuclei (syncytia). Anaplastic nuclei are variable and bizarre in size and shape.
invasion or infiltration (medical literature uses these terms as synonymous equivalents. However, for clarity, the articles that follow adhere to a convention that they mean slightly different things; this convention is not followed outside these articles):
Invasion or invasiveness is the spatial expansion of the tumor through uncontrolled mitosis, in the sense that the neoplasm invades the space occupied by adjacent tissue, thereby pushing the other tissue aside and eventually compressing the tissue. Often these tumors are associated with clearly outlined tumors in imaging.
Infiltration is the behavior of the tumor either to grow (microscopic) tentacles that push into the surrounding tissue (often making the outline of the tumor undefined or diffuse) or to have tumor cells "seeded" into the tissue beyond the circumference of the tumorous mass; this does not mean that an infiltrative tumor does not take up space or does not compress the surrounding tissue as it grows, but an infiltrating neoplasm makes it difficult to say where the tumor ends and the healthy tissue starts.
metastasis (spread to other locations in the body via lymph or blood).
Of the above malignant characteristics, some elements do not apply to primary neoplasms of the brain:
Primary brain tumors rarely metastasize to other organs; some forms of primary brain tumors can metastasize but will not spread outside the intracranial cavity or the central spinal canal. Due to the BBB, cancerous cells of a primary neoplasm cannot enter the bloodstream and get carried to another location in the body. (Occasional isolated case reports suggest spread of certain brain tumors outside the central nervous system, e.g. bone metastasis of glioblastoma.[64])
Primary brain tumors generally are invasive (i.e. they will expand spatially and intrude into the space occupied by other brain tissue and compress those brain tissues); however, some of the more malignant primary brain tumors will infiltrate the surrounding tissue.
By genetics
In 2016, the WHO restructured their classifications of some categories of gliomas to include distinct genetic mutations that have been useful in differentiating tumor types, prognoses, and treatment responses. Genetic mutations are typically detected via immunohistochemistry, a technique that visualizes the presence or absence of a targeted protein via staining.[42]
Mutations in IDH1 and IDH2 genes are commonly found in low-grade gliomas
Loss of both IDH genes combined with loss of chromosome arms 1p and 19q indicates the tumor is an oligodendroglioma[65]
Loss of TP53 and ATRX characterizes astrocytomas
Genes EGFR, TERT, and PTEN, are commonly altered in gliomas and are useful in differentiating tumor grade and biology[42]
Specific types
Main article: WHO classification of the tumors of the central nervous system
Anaplastic astrocytoma, Anaplastic oligodendroglioma, Astrocytoma, Central neurocytoma, Choroid plexus carcinoma, Choroid plexus papilloma, Choroid plexus tumor, Colloid cyst, Dysembryoplastic neuroepithelial tumour, Ependymal tumor, Fibrillary astrocytoma, Giant-cell glioblastoma, Glioblastoma, Gliomatosis cerebri, Gliosarcoma, Hemangiopericytoma, Medulloblastoma, Medulloepithelioma, Meningeal carcinomatosis, Neuroblastoma, Neurocytoma, Oligoastrocytoma, Oligodendroglioma, Optic nerve sheath meningioma, Pediatric ependymoma, Pilocytic astrocytoma, Pinealoblastoma, Pineocytoma, Pleomorphic anaplastic neuroblastoma, Pleomorphic xanthoastrocytoma, Primary central nervous system lymphoma, Sphenoid wing meningioma, Subependymal giant cell astrocytoma, Subependymoma, Trilateral retinoblastoma.
Treatment
A medical team generally assesses the treatment options and presents them to the person affected and their family. Various types of treatment are available depending on tumor type and location, and may be combined to produce the best chances of survival:[60]
Surgery:[60] complete or partial resection of the tumor with the objective of removing as many tumor cells as possible.
Radiotherapy:[60] the most commonly used treatment for brain tumors; the tumor is irradiated with beta, x rays or gamma rays.
Chemotherapy:[60] a treatment option for cancer, however, it is not always used to treat brain tumors as the blood–brain barrier can prevent some drugs from reaching the cancerous cells.
A variety of experimental therapies are available through clinical trials.
Survival rates in primary brain tumors depend on the type of tumor, age, functional status of the patient, the extent of surgical removal and other factors specific to each case.[66]
Standard care for anaplastic oligodendrogliomas and anaplastic oligoastrocytomas is surgery followed by radiotherapy. One study found a survival benefit for the addition of chemotherapy to radiotherapy after surgery, compared with radiotherapy alone.[67]
Surgery
The primary and most desired course of action described in medical literature is surgical removal (resection) via craniotomy.[60] Minimally invasive techniques are becoming the dominant trend in neurosurgical oncology.[68] The main objective of surgery is to remove as many tumor cells as possible, with complete removal being the best outcome and cytoreduction ("debulking") of the tumor otherwise. A Gross Total Resection (GTR) occurs when all visible signs of the tumor are removed, and subsequent scans show no apparent tumor.[69] In some cases access to the tumor is impossible and impedes or prohibits surgery.
Many meningiomas, with the exception of some tumors located at the skull base, can be successfully removed surgically. Most pituitary adenomas can be removed surgically, often using a minimally invasive approach through the nasal cavity and skull base (trans-nasal, trans-sphenoidal approach). Large pituitary adenomas require a craniotomy (opening of the skull) for their removal. Radiotherapy, including stereotactic approaches, is reserved for inoperable cases.[70]
Several current research studies aim to improve the surgical removal of brain tumors by labeling tumor cells with 5-aminolevulinic acid that causes them to fluoresce.[71] Postoperative radiotherapy and chemotherapy are integral parts of the therapeutic standard for malignant tumors.[72][73]
Multiple metastatic tumors are generally treated with radiotherapy and chemotherapy rather than surgery and the prognosis in such cases is determined by the primary tumor, and is generally poor.
Radiation therapy
The goal of radiation therapy is to kill tumor cells while leaving normal brain tissue unharmed. In standard external beam radiation therapy, multiple treatments of standard-dose "fractions" of radiation are applied to the brain. This process is repeated for a total of 10 to 30 treatments, depending on the type of tumor. This additional treatment provides some patients with improved outcomes and longer survival rates.[citation needed]
Radiosurgery is a treatment method that uses computerized calculations to focus radiation at the site of the tumor while minimizing the radiation dose to the surrounding brain. Radiosurgery may be an adjunct to other treatments, or it may represent the primary treatment technique for some tumors. Forms used include stereotactic radiosurgery, such as Gamma knife, Cyberknife or Novalis Tx radiosurgery.[74][unreliable medical source?]
Radiotherapy is the most common treatment for secondary brain tumors. The amount of radiotherapy depends on the size of the area of the brain affected by cancer. Conventional external beam "whole-brain radiotherapy treatment" (WBRT) or "whole-brain irradiation" may be suggested if there is a risk that other secondary tumors will develop in the future.[75] Stereotactic radiotherapy is usually recommended in cases involving fewer than three small secondary brain tumors. Radiotherapy may be used following, or in some cases in place of, resection of the tumor. Forms of radiotherapy used for brain cancer include external beam radiation therapy, the most common, and brachytherapy and proton therapy, the last especially used for children.
People who receive stereotactic radiosurgery (SRS) and whole-brain radiation therapy (WBRT) for the treatment of metastatic brain tumors have more than twice the risk of developing learning and memory problems than those treated with SRS alone.[76][77] Results of a 2021 systematic review found that when using SRS as the initial treatment, survival or death related to brain metastasis was not greater than alone versus SRS with WBRT.[78]
Postoperative conventional daily radiotherapy improves survival for adults with good functional well-being and high grade glioma compared to no postoperative radiotherapy. Hypofractionated radiation therapy has similar efficacy for survival as compared to conventional radiotherapy, particularly for individuals aged 60 and older with glioblastoma.[79]
Chemotherapy
Patients undergoing chemotherapy are administered drugs designed to kill tumor cells.[60] Although chemotherapy may improve overall survival in patients with the most malignant primary brain tumors, it does so in only about 20 percent of patients. Chemotherapy is often used in young children instead of radiation, as radiation may have negative effects on the developing brain. The decision to prescribe this treatment is based on a patient's overall health, type of tumor, and extent of cancer. The toxicity and many side effects of the drugs, and the uncertain outcome of chemotherapy in brain tumors puts this treatment further down the line of treatment options with surgery and radiation therapy preferred.[80]
UCLA Neuro-Oncology publishes real-time survival data for patients with a diagnosis of glioblastoma. They are the only institution in the United States that displays how brain tumor patients are performing on current therapies. They also show a listing of chemotherapy agents used to treat high-grade glioma tumors.[81]
Genetic mutations have significant effects on the effectiveness of chemotherapy. Gliomas with IDH1 or IDH2 mutations respond better to chemotherapy than those without the mutation. Loss of chromosome arms 1p and 19q also indicate better response to chemoradiation.[42]
Other
A shunt may be used to relieve symptoms caused by intracranial pressure, by reducing the build-up of fluid (hydrocephalus) caused by the blockage of the free flow of cerebrospinal fluid.[82]
Prognosis
The prognosis of brain cancer depends on the type of cancer diagnosed. Medulloblastoma has a good prognosis with chemotherapy, radiotherapy, and surgical resection while glioblastoma has a median survival of only 15 months even with aggressive chemoradiotherapy and surgery.[83] Brainstem gliomas have the poorest prognosis of any form of brain cancer, with most patients dying within one year, even with therapy that typically consists of radiation to the tumor along with corticosteroids. However, one type, focal brainstem gliomas in children, seems open to exceptional prognosis and long-term survival has frequently been reported.[84]
Prognosis is also affected by presentation of genetic mutations. Certain mutations provide better prognosis than others. IDH1 and IDH2 mutations in gliomas, as well as deletion of chromosome arms 1p and 19q, generally indicate better prognosis. TP53, ATRX, EGFR, PTEN, and TERT mutations are also useful in determining prognosis.[42]
Glioblastoma
Main article: Glioblastoma
Glioblastoma is the most aggressive (grade 4) and most common form of a malignant primary brain tumor. Even when aggressive multimodality therapy consisting of radiotherapy, chemotherapy, and surgical excision is used, median survival is only 15–18 months.[83] Standard therapy for glioblastoma consists of maximal surgical resection of the tumor, followed by radiotherapy between two and four weeks after the surgical procedure to remove the cancer, then by chemotherapy, such as temozolomide.[85] Most patients with glioblastoma take a corticosteroid, typically dexamethasone, during their illness to relieve symptoms. Experimental treatments include targeted therapy, gamma knife radiosurgery,[86] boron neutron capture therapy, gene therapy, and chemowafer implants.[87][88]
Oligodendrogliomas
Main article: Oligodendroglioma
Oligodendrogliomas are incurable but slowly progressive malignant brain tumors. They can be treated with surgical resection, chemotherapy, radiotherapy or a combination. For some suspected low-grade (grade II) tumors, only a course of watchful waiting and symptomatic therapy is opted for. These tumors show co-deletions of the p and q arms of chromosome 1 and chromosome 19 respectively (1p19q co-deletion) and have been found to be especially chemosensitive with one report claiming them to be one of the most chemosensitive tumors.[83][89] A median survival of up to 16.7 years has been reported for grade II oligodendrogliomas.[90]
Acoustic neuroma
Acoustic neuromas are non-cancerous tumors.[91] They can be treated with surgery, radiation therapy, or observation. Early intervention with surgery or radiation is recommended to prevent progressive hearing loss.[92]
Epidemiology
Figures for incidences of cancers of the brain show a significant difference between more- and less-developed countries (the less-developed countries have lower incidences of tumors of the brain).[93] This could be explained by undiagnosed tumor-related deaths (patients in extremely poor situations do not get diagnosed, simply because they do not have access to the modern diagnostic facilities required to diagnose a brain tumor) and by deaths caused by other poverty-related causes that preempt a patient's life before tumors develop or tumors become life-threatening. Nevertheless, statistics suggest that certain forms of primary brain tumors are more common among certain populations.[94]
The incidence of low-grade astrocytoma has not been shown to vary significantly with nationality. However, studies examining the incidence of malignant central nervous system (CNS) tumors have shown some variation with national origin. Since some high-grade lesions arise from low-grade tumors, these trends are worth mentioning. Specifically, the incidence of CNS tumors in the United States, Israel, and the Nordic countries is relatively high, while Japan and Asian countries have a lower incidence. These differences probably reflect some biological differences as well as differences in pathologic diagnosis and reporting.[95] Worldwide data on incidence of cancer can be found at the WHO (World Health Organization) and is handled by the IARC (International Agency for Research on Cancer) located in France.[96]
United States
In the United States in 2015, approximately 166,039 people were living with brain or other central nervous system tumors. Over 2018, it was projected that there would be 23,880 new cases of brain tumors and 16,830 deaths in 2018 as a result,[94] accounting for 1.4 percent of all cancers and 2.8 percent of all cancer deaths.[97] Median age of diagnosis was 58 years old, while median age of death was 65. Diagnosis was slightly more common in males, at approximately 7.5 cases per 100 000 people, while females saw 2 fewer at 5.4. Deaths as a result of brain cancer were 5.3 per 100 000 for males, and 3.6 per 100 000 for females, making brain cancer the 10th leading cause of cancer death in the United States. Overall lifetime risk of developing brain cancer is approximated at 0.6 percent for men and women.[94][98]
UK
Brain, other CNS or intracranial tumors are the ninth most common cancer in the UK (around 10,600 people were diagnosed in 2013), and it is the eighth most common cause of cancer death (around 5,200 people died in 2012).[99] White British patients with brain tumour are 30% more likely to die within a year of diagnosis than patients from other ethnicities. The reason for this is unknown.[100]
Children
In the United States more than 28,000 people under 20 are estimated to have a brain tumor.[101] About 3,720 new cases of brain tumors are expected to be diagnosed in those under 15 in 2019.[102] Higher rates were reported in 1985–1994 than in 1975–1983. There is some debate as to the reasons; one theory is that the trend is the result of improved diagnosis and reporting, since the jump occurred at the same time that MRIs became available widely, and there was no coincident jump in mortality. Central nervous system tumors make up 20–25 percent of cancers in children.[103][97][104]
The average survival rate for all primary brain cancers in children is 74%.[101] Brain cancers are the most common cancer in children under 19, are result in more death in this group than leukemia.[105] Younger people do less well.[106]
The most common brain tumor types in children (0–14) are: pilocytic astrocytoma, malignant glioma, medulloblastoma, neuronal and mixed neuronal-glial tumors, and ependymoma.[107]
In children under 2, about 70% of brain tumors are medulloblastomas, ependymomas, and low-grade gliomas. Less commonly, and seen usually in infants, are teratomas and atypical teratoid rhabdoid tumors.[108] Germ cell tumors, including teratomas, make up just 3% of pediatric primary brain tumors, but the worldwide incidence varies significantly.[109]
In the UK, 429 children aged 14 and under are diagnosed with a brain tumour on average each year, and 563 children and young people under the age of 19 are diagnosed.[110]
Research
Immunotherapy
Cancer immunotherapy is being actively studied. For malignant gliomas no therapy has been shown to improve life expectancy as of 2015.[111]
Vesicular stomatitis virus
See also: Oncolytic virus
In 2000, researchers used the vesicular stomatitis virus (VSV) to infect and kill cancer cells without affecting healthy cells.[112][113]
Retroviral replicating vectors
A brainstem glioma in four-year-old. MRI, sagittal, without contrast
Led by Prof. Nori Kasahara, researchers from USC, who are now at UCLA, reported in 2001 the first successful example of applying the use of retroviral replicating vectors towards transducing cell lines derived from solid tumors.[114] Building on this initial work, the researchers applied the technology to in vivo models of cancer and in 2005 reported a long-term survival benefit in an experimental brain tumor animal model.[115][unreliable medical source?] Subsequently, in preparation for human clinical trials, this technology was further developed by Tocagen (a pharmaceutical company primarily focused on brain cancer treatments) as a combination treatment (Toca 511 & Toca FC). This has been under investigation since 2010 in a Phase I/II clinical trial for the potential treatment of recurrent high-grade glioma including glioblastoma and anaplastic astrocytoma. No results have yet been published.[116]
Non-invasive detection
Efforts to detect and monitor development and treatment response of brain tumors by liquid biopsy from blood, cerebrospinal fluid or urine, are in the early stages of development.[117][118]
See also
Brain
Tumor
Nervous system neoplasm
List of brain tumor cases
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External links
Classification
D
ICD-10: C71, D33,ICD-9-CM: 191, 225.0MeSH: D001932DiseasesDB: 30781
External resources
MedlinePlus: 007222eMedicine: emerg/334NCI: Brain tumor
Wikimedia Commons has media related to Brain tumors.
Brain and CNS cancers at Curlie
Brain tumour information from Cancer Research UK
Neuro-Oncology: Cancer Management Guidelines
MedPix Teaching File MR Scans of Primary Brain Lymphoma, etc.
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he lungs are the central organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. The pleurae, which are thin, smooth, and moist, serve to reduce friction between the lungs and chest wall during breathing, allowing for easy and effortless movements of the lungs.
Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their different muscles to support and foster breathing. In earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech possible.
Humans have two lungs, one on the left and one on the right. They are situated within the thoracic cavity of the chest. The right lung is bigger and heavier than the left, which shares space in the chest with the heart. The lungs together weigh approximately 1.3 kilograms (2.9 pounds). The lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, and which receive air breathed in via the conducting zone. The conducting zone ends at the terminal bronchioles. These divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that contain the alveoli, where gas exchange takes place. Alveoli are also sparsely present on the walls of the respiratory bronchioles and alveolar ducts. Together, the lungs contain approximately 2,400 kilometres (1,500 miles) of airways and 300 to 500 million alveoli. Each lung is enclosed within a pleural sac of two membranes called pleurae; the membranes are separated by a film of pleural fluid, which allows the inner and outer membranes to slide over each other whilst breathing takes place, without much friction. The inner pleura also divides each lung into sections called lobes. The right lung has three lobes and the left has two. The lobes are further divided into bronchopulmonary segments and pulmonary lobules. The lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purposes of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the tissue of the lungs, in the bronchial circulation. Deoxygenated blood travels from the heart through the pulmonary artery to the lungs to be oxygenated in capillaries of alveoli. After the blood is oxygenated, it returns to the heart through the pulmonary vein to be sent to the rest of the body.[1][2]
The tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer. Chronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances. A number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust. Diseases such as bronchitis can also affect the respiratory tract. Medical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων "lung") as in pneumonia.
In embryonic development, the lungs begin to develop as an outpouching of the foregut, a tube which goes on to form the upper part of the digestive system. When the lungs are formed the fetus is held in the fluid-filled amniotic sac and so they do not function to breathe. Blood is also diverted from the lungs through the ductus arteriosus. At birth, however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire. The lungs only fully develop in early childhood.
Structure
Anatomy
The lungs are located in the chest on either side of the heart in the rib cage. They are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm.[3] The apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib. The lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.[3]
The left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this.[4][5] The front and outer sides of the lungs face the ribs, which make light indentations on their surfaces. The medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels, and the carina where the trachea divides into the two main bronchi.[5] The cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart.
Both lungs have a central recession called the hilum, where the blood vessels and airways pass into the lungs making up the root of the lung.[6] There are also bronchopulmonary lymph nodes on the hilum.[5]
The lungs are surrounded by the pulmonary pleurae. The pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs. Between the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid.
Lobes
Lobes and bronchopulmonary segments[7]
Right lung Left lung
Upper
Apical
Posterior
Anterior
Middle
Lateral
Medial
Lower
Superior
Medial
Anterior
Lateral
Posterior
Upper
Apicoposterior
Anterior
Lingula
Superior
Inferior
Lower
Superior
Anteriomedial
Lateral
Posterior
Each lung is divided into sections called lobes by the infoldings of the visceral pleura as fissures. Lobes are divided into segments, and segments have further divisions as lobules. There are three lobes in the right lung and two lobes in the left lung.
Fissures
The fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion.[8][9] The right lung is divided into three lobes by a horizontal fissure, and an oblique fissure. The left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung. In the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe. The lower, oblique fissure separates the lower lobe from the middle and upper lobes.[3][9]
Variations in the fissures are fairly common being either incompletely formed or present as an extra fissure as in the azygos fissure, or absent. Incomplete fissures are responsible for interlobar collateral ventilation, airflow between lobes which is unwanted in some lung volume reduction procedures.[8]
Segments
The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung. The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments. Each bronchopulmonary segment has its own (segmental) bronchus and arterial supply.[10] Segments for the left and right lung are shown in the table.[7] The segmental anatomy is useful clinically for localising disease processes in the lungs.[7] A segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue.[11]
The left lung
The right lung
The left lung (left) and right lung (right). The lobes of the lungs can be seen, and the central root of the lung is also present.
Right lung
The right lung has both more lobes and segments than the left. It is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal.[12] The upper, horizontal fissure, separates the upper from the middle lobe. It begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced back to the hilum.[3] The lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.[3][9]
The mediastinal surface of the right lung is indented by a number of nearby structures. The heart sits in an impression called the cardiac impression. Above the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right brachiocephalic vein; behind this, and close to the top of the lung is a groove for the brachiocephalic artery. There is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.[5]
The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb)[13] and in women of 100–590 g (0.22–1.30 lb).[14]
Left lung
The left lung is divided into two lobes, an upper and a lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.[3] The left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula. Its name means "little tongue". The lingula on the left lung serves as an anatomic parallel to the middle lobe on the right lung, with both areas being predisposed to similar infections and anatomic complications.[15][16] There are two bronchopulmonary segments of the lingula: superior and inferior.[3]
The mediastinal surface of the left lung has a large cardiac impression where the heart sits. This is deeper and larger than that on the right lung, at which level the heart projects to the left.[5]
On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta. The left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung. A shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein. The esophagus may sit in a wider shallow impression at the base of the lung.[5]
By standard reference range, the weight of the left lung is 110–675 g (0.243–1.488 lb)[13] in men and 105–515 g (0.231–1.135 lb) in women.[14]
Illustrations
Chest CT (axial lung window)
Chest CT (axial lung window)
Chest CT (coronal lung window)
Chest CT (coronal lung window)
Chest CT (axial lung window)
Chest CT (coronal lung window)
"Meet the lungs" from Khan Academy
Pulmonology video
3D anatomy of the lung lobes and fissures.
Microanatomy
Cross-sectional detail of the lung
The lungs are part of the lower respiratory tract, and accommodate the bronchial airways when they branch from the trachea. The bronchial airways terminate in alveoli which make up the functional tissue (parenchyma) of the lung, and veins, arteries, nerves, and lymphatic vessels.[5][17] The trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa. The smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli.[18] The lungs are supplied with the largest lymphatic drainage system of any other organ in the body.[19] Each lung is surrounded by a serous membrane of visceral pleura, which has an underlying layer of loose connective tissue attached to the substance of the lung.[20]
Connective tissue
Thick elastic fibres from the visceral pleura (outer lining) of lung
TEM image of collagen fibres in a cross sectional slice of mammalian lung tissue
The connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls. Elastin is the key protein of the extracellular matrix and is the main component of the elastic fibres.[21] Elastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance. It is also responsible for the elastic recoil needed. Elastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions.[21] The connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance. The alveoli have interconnecting air passages in their walls known as the pores of Kohn.[22]
Respiratory epithelium
Main article: Respiratory epithelium
All of the lower respiratory tract including the trachea, bronchi, and bronchioles is lined with respiratory epithelium. This is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus, ciliated cells, basal cells, and in the terminal bronchioles–club cells with actions similar to basal cells, and macrophages. The epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL), the composition of which is tightly regulated and determines how well mucociliary clearance works.[23]
Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium,[24] though they only account for around 0.5 percent of the total epithelial population.[25] PNECs are innervated airway epithelial cells that are particularly focused at airway junction points.[25] These cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products. Cytoplasmic processes from the pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas.[26]
Bronchial airways
In the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open.[27]: 472 Bronchioles are too narrow to support cartilage and their walls are of smooth muscle, and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium.[27]: 472 The absence of cartilage in the terminal bronchioles gives them an alternative name of membranous bronchioles.[28]
A lobule of the lung enclosed in septa and supplied by a terminal bronchiole that branches into the respiratory bronchioles. Each respiratory bronchiole supplies the alveoli held in each acinus accompanied by a pulmonary artery branch.
Respiratory zone
The conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles. This marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli.[29] An acinus measures up to 10 mm in diameter.[30] A primary pulmonary lobule is the part of the lung distal to the respiratory bronchiole.[31] Thus, it includes the alveolar ducts, sacs, and alveoli but not the respiratory bronchioles.[32]
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Further reading
Dr D.R. Johnson: Introductory anatomy, respiratory system, leeds.ac.uk
Franlink Institute Online: The Respiratory System, sln.fi.edu
Avian lungs and respiration, people.eku.edu
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he stomach is a muscular, hollow organ in the upper gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach is involved in the gastric phase of digestion, following the cephalic phase in which the sight and smell of food and the act of chewing are stimuli. In the stomach a chemical breakdown of food takes place by means of secreted digestive enzymes and gastric acid.
The stomach is located between the esophagus and the small intestine. The pyloric sphincter controls the passage of partially digested food (chyme) from the stomach into the duodenum, the first and shortest part of the small intestine, where peristalsis takes over to move this through the rest of the intestines.
Structure
In the human digestive system, the stomach lies between the esophagus and the duodenum (the first part of the small intestine). It is in the left upper quadrant of the abdominal cavity. The top of the stomach lies against the diaphragm. Lying behind the stomach is the pancreas. A large double fold of visceral peritoneum called the greater omentum hangs down from the greater curvature of the stomach. Two sphincters keep the contents of the stomach contained; the lower esophageal sphincter (found in the cardiac region), at the junction of the esophagus and stomach, and the pyloric sphincter at the junction of the stomach with the duodenum.
The stomach is surrounded by parasympathetic (stimulant) and sympathetic (inhibitor) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles.
The stomach is distensible, and can normally expand to hold about one litre of food.[3] In a newborn human baby the stomach will only be able to hold about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres.[4][5] Although volumes of up to 15 L have been observed in extreme circumstances.[6]
Sections
"Cardia" redirects here. For the ancient Greek colony, see Cardia (Thrace).
Diagram showing parts of the stomach
The human stomach can be divided into four sections, beginning at the cardia followed by the fundus, the body and the pylorus.[7][8]
The gastric cardia is where the contents of the esophagus empty from the gastroesophageal sphincter into the cardiac orifice, the opening into the gastric cardia.[9][8] A cardiac notch at the left of the cardiac orifice, marks the beginning of the greater curvature of the stomach. A horizontal line across from the cardiac notch gives the dome-shaped region called the fundus.[8] The cardia is a very small region of the stomach that surrounds the esophageal opening.[8]
The fundus (from Latin 'bottom') is formed in the upper curved part.
The body or corpus is the main, central region of the stomach.
The pylorus opens to the body of the stomach. The pylorus (from Greek 'gatekeeper') connects the stomach to the duodenum at the pyloric sphincter.
The cardia is defined as the region following the "z-line" of the gastroesophageal junction, the point at which the epithelium changes from stratified squamous to columnar. Near the cardia is the lower esophageal sphincter.[9]
Anatomical proximity
The stomach bed refers to the structures upon which the stomach rests in mammals.[10][11] These include the tail of the pancreas, splenic artery, left kidney, left suprarenal gland, transverse colon and its mesocolon, and the left crus of diaphragm, and the left colic flexure. The term was introduced around 1896 by Philip Polson of the Catholic University School of Medicine, Dublin. However this was brought into disrepute by surgeon anatomist J Massey.[12][13][14]
Blood supply
Schematic image of the blood supply to the human stomach: left and right gastric artery, left and right gastroepiploic artery and short gastric arteries[15]
The lesser curvature of the human stomach is supplied by the right gastric artery inferiorly and the left gastric artery superiorly, which also supplies the cardiac region. The greater curvature is supplied by the right gastroepiploic artery inferiorly and the left gastroepiploic artery superiorly. The fundus of the stomach, and also the upper portion of the greater curvature, is supplied by the short gastric arteries, which arise from the splenic artery.
Lymphatic drainage
The two sets of gastric lymph nodes drain the stomach.
Microanatomy
Wall
Main article: Gastrointestinal wall
The gastrointestinal wall of the human stomach
Layers of the gastrointestinal wall of which the stomach is a dilated part
Like the other parts of the gastrointestinal wall, the human stomach wall from inner to outer, consists of a mucosa, submucosa, muscular layer, subserosa and serosa.[16]
The inner part of the stomach wall is the gastric mucosa a mucous membrane that forms the lining of the stomach. the membrane consists of an outer layer of columnar epithelium, a lamina propria, and a thin layer of smooth muscle called the muscularis mucosa. Beneath the mucosa lies the submucosa, consisting of fibrous connective tissue.[17] Meissner's plexus is in this layer interior to the oblique muscle layer.[18]
Outside of the submucosa lies the muscular layer. It consists of three layers of muscular fibres, with fibres lying at angles to each other. These are the inner oblique, middle circular, and outer longitudinal layers.[19] The presence of the inner oblique layer is distinct from other parts of the gastrointestinal tract, which do not possess this layer.[20] The stomach contains the thickest muscular layer consisting of three layers, thus maximum peristalsis occurs here.
The inner oblique layer: This layer is responsible for creating the motion that churns and physically breaks down the food. It is the only layer of the three which is not seen in other parts of the digestive system. The antrum has thicker skin cells in its walls and performs more forceful contractions than the fundus.
The middle circular layer: At this layer, the pylorus is surrounded by a thick circular muscular wall, which is normally tonically constricted, forming a functional (if not anatomically discrete) pyloric sphincter, which controls the movement of chyme into the duodenum. This layer is concentric to the longitudinal axis of the stomach.
The myenteric plexus (Auerbach's plexus) is found between the outer longitudinal and the middle circular layer and is responsible for the innervation of both (causing peristalsis and mixing).
The outer longitudinal layer is responsible for moving the semi-digested food towards the pylorus of the stomach through muscular shortening.
To the outside of the muscular layer lies a serosa, consisting of layers of connective tissue continuous with the peritoneum.
Smooth mucosa along the inside of the lesser curvature forms a passageway - the gastric canal that fast-tracks liquids entering the stomach, to the pylorus.[8]
Glands
Main article: Gastric glands
Diagram showing gastric pits (13) gastric glands (12) lamina propria (10) epithelium (11)
Histology of normal fundic mucosa. Fundic glands are simple, branched tubular glands that extend from the bottom of the gastric pits to the muscularis mucosae; the more distinctive cells are parietal cells. H&E stain.
Histology of normal antral mucosa. Antral mucosa is formed by branched coiled tubular glands lined by secretory cells similar in appearance to the surface mucus cells. H&E stain.
The mucosa lining the stomach is lined with gastric pits, which receive gastric juice, secreted by between 2 and 7 gastric glands.[citation needed] Gastric juice is an acidic fluid containing hydrochloric acid and digestive enzymes.[21] The glands contains a number of cells, with the function of the glands changing depending on their position within the stomach.[citation needed]
Within the body and fundus of the stomach lie the fundic glands. In general, these glands are lined by column-shaped cells that secrete a protective layer of mucus and bicarbonate. Additional cells present include parietal cells that secrete hydrochloric acid and intrinsic factor, chief cells that secrete pepsinogen (this is a precursor to pepsin- the highly acidic environment converts the pepsinogen to pepsin), and neuroendocrine cells that secrete serotonin.[22][citation needed]
Glands differ where the stomach meets the esophagus and near the pylorus.[23] Near the gastroesophageal junction lie cardiac glands, which primarily secrete mucus.[22] They are fewer in number than the other gastric glands and are more shallowly positioned in the mucosa. There are two kinds - either simple tubular glands with short ducts or compound racemose resembling the duodenal Brunner's glands.[citation needed] Near the pylorus lie pyloric glands located in the antrum of the pylorus. They secrete mucus, as well as gastrin produced by their G cells.[24][citation needed]
Gene and protein expression
Further information: Bioinformatics § Gene and protein expression
About 20,000 protein-coding genes are expressed in human cells and nearly 70% of these genes are expressed in the normal stomach.[25][26] Just over 150 of these genes are more specifically expressed in the stomach compared to other organs, with only some 20 genes being highly specific. The corresponding specific proteins expressed in stomach are mainly involved in creating a suitable environment for handling the digestion of food for uptake of nutrients. Highly stomach-specific proteins include gastrokine-1 expressed in the mucosa; pepsinogen and lipase, expressed in gastric chief cells; and a gastric ATPase and gastric intrinsic factor, expressed in parietal cells.[27]
Development
In the early part of the development of the human embryo, the ventral part of the embryo abuts the yolk sac. During the third week of development, as the embryo grows, it begins to surround parts of the yolk sac. The enveloped portions form the basis for the adult gastrointestinal tract.[28] The sac is surrounded by a network of vitelline arteries and veins. Over time, these arteries consolidate into the three main arteries that supply the developing gastrointestinal tract: the celiac artery, superior mesenteric artery, and inferior mesenteric artery. The areas supplied by these arteries are used to define the foregut, midgut, and hindgut.[28] The surrounded sac becomes the primitive gut. Sections of this gut begin to differentiate into the organs of the gastrointestinal tract, and the esophagus, and stomach form from the foregut.[28]
As the stomach rotates during early development, the dorsal and ventral mesentery rotate with it; this rotation produces a space anterior to the expanding stomach called the greater sac, and a space posterior to the stomach called the lesser sac. After this rotation the dorsal mesentery thins and forms the greater omentum, which is attached to the greater curvature of the stomach. The ventral mesentery forms the lesser omentum, and is attached to the developing liver. In the adult, these connective structures of omentum and mesentery form the peritoneum, and act as an insulating and protective layer while also supplying organs with blood and lymph vessels as well as nerves.[29] Arterial supply to all these structures is from the celiac trunk, and venous drainage is by the portal venous system. Lymph from these organs is drained to the prevertebral celiac nodes at the origin of the celiac artery from the aorta.
Function
Digestion
Further information: Human digestive system
See also: Gastric acid
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External links
Look up stomach in Wiktionary, the free dictionary.
Stomach at the Human Protein Atlas
Digestion of proteins in the stomach or tiyan (archived 10 March 2007)
Site with details of how ruminants process food (archived 27 October 2009)
Control of Gastric Emptying (Archived 2019-11-12 at the Wayback Machine)
vte
Human regional anatomy
vte
Anatomy of the gastrointestinal tract, excluding the mouth
Upper
Pharynx
MusclesSpaces peripharyngeal retropharyngeal parapharyngeal retrovisceral dangerprevertebralPterygomandibular raphePharyngeal rapheBuccopharyngeal fasciaPharyngobasilar fasciaPyriform sinus
Esophagus
Sphincters upperlowerglandscrop
Stomach
Curvatures greaterlesserAngular incisureCardiaBodyFundusPylorus antrumcanalsphincterGastric mucosaGastric foldsMicroanatomy Gastric pitsGastric glandsCardiac glandsFundic glandsPyloric glandsFoveolar cellsParietal cellsGastric chief cellsEnterochromaffin-like cells
Lower
Small intestine
Microanatomy
Intestinal villi MicrovilliIntestinal glandsEnterocytesEnteroendocrine cellsGoblet cellsPaneth cells
Duodenum
Suspensory muscleMajor duodenal papillaMinor duodenal papillaDuodenojejunal flexureBrunner's glands
Jejunum
No substructures
Ileum
Ileocecal valvePeyer's patchesMicrofold cells
Large intestine
Cecum
Appendix
Colon
Ascending colonHepatic flexureTransverse colonSplenic flexureDescending colonSigmoid colonContinuous taenia colihaustraepiploic appendix
Rectum
Transverse foldsAmpulla
Anal canal
AnusAnal columnsAnal valvesAnal sinusesPectinate lineInternal anal sphincterIntersphincteric grooveExternal anal sphincter
Wall
Serosa / AdventitiaSubserosaMuscular layerSubmucosaCircular foldsMuc
Positive affectivity (PA) is a human characteristic that describes how much people experience positive affects (sensations, emotions, sentiments); and as a consequence how they interact with others and with their surroundings.[1]
People with high positive affectivity are typically enthusiastic, energetic, confident, active, and alert. Research has linked positive affectivity with an increase in longevity, better sleep, and a decrease in stress hormones.[2][3] People with a high positive affectivity have healthier coping styles, more positive self-qualities, and are more goal oriented.[4][3] Positive affectivity also promotes an open-minded attitude, sociability, and helpfulness.[1]
Those having low levels of positive affectivity (and high levels of negative affectivity) are characterized by sadness, lethargy, distress, and un-pleasurable engagement (see negative affectivity). Low levels of positive affect are correlated with social anxiety and depression, due to decreased levels of dopamine.[5]
Psychology
Happiness, a feeling of well-being, and high levels of self-esteem are often associated with high levels of positive affectivity, but they are each influenced by negative affectivity as well.[6] Trait PA roughly corresponds to the dominant personality factors of extraversion;[7][8] however, this construct is also influenced by interpersonal components.[6]
Effects
Overall, positive affect results in a more positive outlook, increases problem solving skills, increases social skills, increases activity and projects, and can play a role in motor function.[1][9]
Positive affectivity is an integral part of everyday life.[10] PA helps individuals to process emotional information accurately and efficiently, to solve problems, to make plans, and to earn achievements. The broaden-and-build theory of PA[11][12] suggests that PA broadens people's momentary thought-action repertoires and builds their enduring personal resources.
Research shows that PA relates to different classes of variables, such as social activity and the frequency of pleasant events.[7][13][14][15] PA also strongly relates to life satisfaction.[16] The high energy and engagement, optimism, and social interest characteristic of high-PA individuals suggest that they are more likely to be satisfied with their lives.[7][8] In fact, the content similarities between these affective traits and life satisfaction have led some researchers to view both PA, NA, and life satisfaction as specific indicators of the broader construct of subjective well-being.[17][10]
PA may influence the relationships between variables in organizational research.[18][19] PA increases attentional focus and behavioral repertoire, and these enhanced personal resources can help to overcome or deal with distressing situations. These resources are physical (e.g., better health), social (e.g., social support networks), and intellectual and psychological (e.g., resilience, optimism, and creativity).
PA provides a psychological break or respite from stress,[2] supporting continued efforts to replenish resources depleted by stress.[20][21] Its buffering functions provide a useful antidote to the problems associated with negative emotions and ill health due to stress,[12] as PA reduces allostatic load.[2] Likewise, happy people are better at coping. McCrae and Costa[22] concluded that PA was associated with more mature coping efforts.
Negative affectivity
Main article: Negative affectivity
Positive affectivity (PA) and negative affectivity (NA) are nearly independent of each other;[6] it is possible for a person to be high in both PA and NA, high in one and low in the other, or low in both. Affectivity has been found to be moderately stable over time and across situations (such as working versus relaxing).[6] Positive affectivity may influence an individual's choices in general, particularly their responses to questionnaires.
Neuropsychology
Studies are finding there is a relationship between dopamine release and positive affect in cognitive abilities.[1] For instance, when dopamine levels are low, positive affect can stimulate the release of more dopamine, temporarily increasing cognitive, motor, and emotional processing. Stimulating dopamine release influences several cognitive functions. First, an increase in dopamine in the nigrostriatal system can temporarily relieve motor or cognitive dysfunction, due to Parkinson's.
An increase in dopamine release also influences the mesocorticolimbic system through the VTA cells, increasing mood and open mindedness in older adults. Positive affect also stimulates dopamine production in the prefrontal cortex and the anterior cingulate facilities, which help with processing working memory and executive attention. Lastly, PA indirectly improves memory consolidation in the hippocampus, by increasing acetylcholine release from an increase in dopamine.[1]
Business management
Positive affectivity is a managerial and organizational behavior tool used to create positive environments in the workplace. Through the use of PA, the manager can induce a positive employee experience and culture. "Since affectivity is related to the employee experiences, we expect the employees with high PA to feel considerable organizational support. Their optimism and confidence also helps them discuss their views in a manner characterized by constructive controversy with their supervisor, so that problems are solved and their positive feelings confirmed".[23] Positive Affectivity allows creative problem solving to flourish in an environment where employees are not intimidated to approach managers, therefore employees believe they are playing a key role in the organization in coming forward with solutions. The goal is to maximize PA and minimize any negative affectivity circulating in the business. Negative emotions, such as fear, anger, stress, hostility, sadness, and guilt, increase the predictability of workplace deviance,[24] and therefore reduce the productivity of the business.
Testing
Because there is not a hard-and-fast rule for defining certain levels of positive affectivity, different self-reported assessments use different scales of measure.[6] Several prominent tests are listed below; in each of these, the respondent determines the degree to which a given adjective or phrase accurately characterizes him or her.
Differential Emotions Scale (DES): A PA scale that assesses enjoyment (happy or joyful feelings) and interest (excitement, alertness, curiosity).[6]
Multiple Affect Adjective Checklist – Revised (MAACL-R): Measures PA according to the DES scale and to an additional scale assessing thrill-seeking behavior (i.e., how daring or adventurous the person is).[6]
Profile of Mood States (POMS): Uses vigor scale to assess the domain of PA.[6]
Expanded Form of the Positive and Negative Affect Schedule (PANAS-X): This test uses three main scales: joviality (how cheerful, happy, or lively), self-assurance (how confident and strong), and attentiveness (alertness and concentration).[6]
International Positive and Negative Affect Schedule Short-Form (I-PANAS-SF): This is a brief, 10-item version of the PANAS that has been developed and extensively validated for use in English with both native and non-native English speakers.[25] Internal consistency reliability for the 5-item PA scale is reported to range between .72 and .78.[25]
See also
Affection
Anhedonia
Gratitude
Happiness
Joy
Satisfaction
Surgency
References
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Lazarus, R. S. (1991). Emotion and Adaptation. NY: Oxford Univ. Press.
Khosla, M. (2006 c). Finding benefit in adversity. Manuscript in press.
McCrae, Robert R.; Costa, Paul T. Jr. (June 1986). "Personality, coping, and coping effectiveness in an adult sample". Journal of Personality. 54 (2): 385–404. doi:10.1111/j.1467-6494.1986.tb00401.x.
Hui, Chun; Wong, Alfred; Tjosvold, Dean. "Journal of Occupational and Organizational Psychology (2007), 80, 735–751". Journal of Occupational and Organizational Psychology: 738.
Lee; Kibeom; Allen, Natalie J (2002). "Organizational Citizenship Behavior and Workplace Deviance: The Role of Affect and Cognitions". Journal of Applied Psychology. 87 (1): 131–142. doi:10.1037/0021-9010.87.1.131. PMID 11916207.
Thompson, E.R. (2007). "Development and validation of an internationally reliable short-form of the positive and negative affect schedule (PANAS)" (PDF). Journal of Cross-Cultural Psychology. 38 (2): 227–242. doi:10.1177/0022022106297301. S2CID 145498269.[permanent dead link]
Further reading
Bushman, Bryan B.; Crowley, Susan L. (February 2010). "Is the Structure of Affect Similar for Younger and Older Children? Cross-Sectional Differences in Negative and Positive Affectivity". Journal of Psychoeducational Assessment. 28 (1): 31–39. doi:10.1177/0734282909337584. S2CID 144121162.
Congard, A.; Dauvier, B.; Antoine, P.; Gilles, P. (2011). "Integrating personality, daily life events and emotion: Role of anxiety and positive affect in emotion regulation dynamics" (PDF). Journal of Research in Personality. 45 (4): 372–384. doi:10.1016/j.jrp.2011.04.004.
Grafton, B (2012). "The ups and downs of cognitive bias: Dissociating the attentional characteristics of positive and negative affectivity". Journal of Cognitive Psychology. 24 (1): 33–53. doi:10.1080/20445911.2011.578066. S2CID 145185201.
Lopez, S. J. (2008). Positive psychology: Exploring the best in people. (Vol. 2). Westport, CT: Praeger Publications.
Lopez, S., & Snyder, C. R. (2009). Oxford handbook of positive psychology. (2nd ed.). Oxford, New York: Oxford University Press.
Tomkins, S. S. (1962). Affect, imagery, consciousness. (Vol. I). New York, NY: Springer Publishing Company, Inc.
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Emotions (list)
Emotions
AcceptanceAdmirationAdorationAestheticAffectionAgitationAgonyAmusementAngerAngstAnguishAnnoyanceAnticipationAnxietyApathyArousalAttractionAweBelongingnessBoredomCalmnessCompassionConfidenceConfusionContemptContentmentCourageCrueltyCuriosityDefeatDepressionDesireDisappointmentDisgustDistrustDoubtEcstasyEmbarrassment vicariousEmotion workEmpathyEmptinessEnthrallmentEnthusiasmEnvyEuphoriaExcitementFaithFearFlowFrustrationGratificationGratitudeGreedGriefGuiltHappiness Joie de vivreHatredHiraethHomesicknessHopeHorrorHostilityHumiliationHyggeHysteriaIkigai (sense of purpose)IndulgenceInfatuationInsecurityInspirationInterestIrritationIsolationJealousyJoyKindnessLonelinessLove limerenceat first sightLustMono no awareNeglectNostalgiaOutragePanicPassionPity self-pityPleasurePride grandiosityhubrisinsultvanityRageRegretRejectionReliefRemorseResentmentRevengeSadness melancholySaudadeSchadenfreudeSehnsuchtSentimentalityShameShockShynessSocial connectionSorrowSpiteStress chronicSufferingSurpriseSympathyTrustWonder sense of wonderWorry
Worldviews
CynicismDefeatismNihilismOptimismPessimismReclusionWeltschmerz
Related
Affect consciousnessin educationmeasuresin psychologyAffective computingforecastingneurosciencesciencespectrumAffectivity positivenegativeAppeal to emotionAmygdala hijackEmotion and artand memoryand musicand sexand sleepclassificationevolutionexpressedfunctional accountsgrouphomeostaticin animalsperceptionrecognition in conversationregulation interpersonalworkEmotional aperturebiasblackmailcompetenceconflictcontagiondetachmentdysregulationeatingexhaustionexpression and genderintelligence and bullyingEmpathy quotientintimacyisolationlabilitylaborlateralizationliteracyprosodyreasoningresponsivitysecuritysymbiosisthought methodwell-beingEmotionality boundedEmotions and culturehistoryin decision-makingin the workplacein virtual communicationmoralself-conscioussocialsocial sharingsociologyFeelingGroup affective toneInteractions between the emotional and executive brain systemsJealousy in artMeta-emotionPathognomyPathosSocial emotional developmentStoic passionsTheory affectappraisalconstructed emotiondiscrete emotionsomatic marke
Kindness is a type of behavior marked by acts of generosity, consideration, rendering assistance, or concern for others, without expecting praise or reward in return. It is a subject of interest in philosophy, religion, and psychology.
In Book II of Rhetoric, Aristotle defines kindness as "helpfulness towards someone in need, not in return for anything, nor for the advantage of the helper himself, but for that of the person helped".[1] Friedrich Nietzsche considered kindness and love to be the "most curative herbs and agents in human intercourse".[2] Kindness is one of the Knightly Virtues.[3] In Meher Baba's teachings, God is synonymous with kindness: "God is so kind that it is impossible to imagine His unbounded kindness!"[4]
History
In English, the word kindness dates from approximately 1300, though the word's sense evolved to its current meanings in the late 1300s.[5]
In society
Human mate choice studies suggest that both men and women value kindness in their prospective mates, along with intelligence, physical appearance, attractiveness, and age.[6]
In psychology
Studies at Yale University using games with babies concluded that kindness is inherent to human beings.[7] There are similar studies about the root of empathy in infancy[8] – with motor mirroring developing in the early months of life,[9] and leading (optimally) to the concern shown by children for their peers in distress.[10]: 112
Barbara Taylor and Adam Phillips stressed the element of necessary realism[jargon] in adult kindness, as well as the way "real kindness changes people in the doing of it, often in unpredictable ways".[10]: 96 & 12
2018 Women's March in Missoula, Montana
Behaving kindly may improve a person's measurable well-being. Many studies have tried to test the hypothesis that doing something kind makes a person better off. A meta-analysis of 27 such studies found that the interventions studied (usually measuring short-term effects after brief acts of kindness, in WEIRD research subjects) supported the hypothesis that acting more kind improves your well-being.[11]
Weaponized kindness
Some thinkers have suggested that kindness can be weaponized to discourage enemies:
If thine enemy be hungry, give him bread; and if he be thirsty, give him water to drink; for by doing so thou shalt heap coals of fire upon his head.
— Proverbs 25:21–22
You should respond with kindness toward evil done to you, and you will destroy in an evil person that pleasure which he derives from evil.
— Leo Tolstoy[12]
Teaching kindness
Kindness is most often taught from parents to children and is learned through observation and some direct teaching. Studies have shown that through programs and interventions kindness can be taught and encouraged during the first 20 years of life.[13] Further studies show that kindness interventions can help improve wellbeing with comparable results as teaching gratitude.[14] Similar findings have shown that organizational level teaching of kindness can improve wellbeing of adults in college.[15]
See also
Altruism – Principle or practice of concern for the welfare of others
Compassion – Moved or motivated to help others
Empathy – Capacity to understand or feel what another person is experiencing
Generosity – Liberal in giving
Good – Concept in religion, ethics, and philosophy
Good faith – Intention to be fair, open, and honest
Kindness Day UK
Moral character – Steady moral qualities in people
Moral emotions – Variety of social emotions
Reciprocity – Repayment in kind
Pay it forward – Expression for describing the beneficiary of a good deed repaying the kindness to others
Random act of kindness – Nonpremeditated act to cheer up another
Random Acts of Kindness Day – A day to celebrate kindlness
r/K selection theory – Ecological theory concerning the selection of life history traits
The Kindness Offensive – North London group known for random acts of kindness
World Kindness Day – International observance on 13 November
References
Aristotle. Rhetoric. Translated by Roberts, W. Rhys. Book 2, chapter 7. Archived from the original on December 13, 2004. Retrieved 2005-11-22.
Nietzsche, Friedrich Wilhelm (1996) [1878]. "On the History of Moral Feelings". Menschliches, Allzumenschiles [Human, all too human: a book for free spirits]. Translated by Faber, Marion; Lehman, Stephen. University of Nebraska Press. Aphorism 48.
Singla, Parvesh. "Character". The Manual of Life: Understanding Karma/Right Action. Parvesh singla – via Google Books.[page needed][self-published source?]
Kalchuri, Bhau (1986). Meher Prabhu: Lord Meher. Vol. 11. Myrtle Beach: Manifestation, Inc. p. 3918.
"kindness". Online Etymology Dictionary.
Buss, David M.; et al. (1992). "Sex differences in jealousy: Evolution, physiology, and psychology". Psychological Science. 3 (4): 251–255. doi:10.1111/j.1467-9280.1992.tb00038.x. S2CID 27388562.
Gleitman, Henry; Gross, James; Reisberg, Daniel (2011). Psychology (8th ed.). W.W. Norton & co. ISBN 9780393932508.
"Can Babies Tell Right From Wrong?, Babies at Yale University's Infant Cognition Center respond to "naughty" and "nice" puppets". New York Times (TimesVideo). May 5, 2010. Archived from the original on 2015-07-12.
Goleman, Daniel (1989-03-28). "Researchers Trace Empathy's Roots to Infancy". New York Times. p. C1.
Goleman, Daniel (1996). Emotional Intelligence. London: Bloomsbury. pp. 98–99.
Phillips, Adam; Taylor, Barbara (2009). On Kindness. London.
Curry, Oliver Scott; Rowland, Lee A.; Van Lissa, Caspar J.; Zlotowitz, Sally; McAlaney, John; Whitehouse, Harvey (2018). "Happy to help? A systematic review and meta-analysis of the effects of performing acts of kindness on the well-being of the actor". Journal of Experimental Social Psychology. 76: 320–329. doi:10.1016/j.jesp.2018.02.014.
Tolstoy, Leo (1910). "January 30". A Calendar of Wisdom.
Malti, Tina (2021-09-03). "Kindness: a perspective from developmental psychology". European Journal of Developmental Psychology. 18 (5): 629–657. doi:10.1080/17405629.2020.1837617. ISSN 1740-5629. S2CID 228970189.
Datu, Jesus Alfonso D.; Valdez, Jana Patricia M.; McInerney, Dennis M.; Cayubit, Ryan Francis (May 2022). "The effects of gratitude and kindness on life satisfaction, positive emotions, negative emotions, and COVID-19 anxiety: An online pilot experimental study". Applied Psychology: Health and Well-Being. 14 (2): 347–361. doi:10.1111/aphw.12306. ISSN 1758-0846. PMC 8652666. PMID 34668323.
Datu, Jesus Alfonso D.; Lin, Xunyi (June 2022). "The Mental Health Benefits of kind University Climate: Perception of Kindness at University Relates to Longitudinal Increases in Well-Being". Applied Research in Quality of Life. 17 (3): 1663–1680. doi:10.1007/s11482-021-09981-z. ISSN 1871-2584. S2CID 255275797.
Further reading
Rabbi-Ul-Awwal (July 1998). "What is Kindness to Parents?". Islamic Voice. 12–07 (139). Archived from the original on 2019-11-28. Retrieved 2008-11-26.
El-Sayed M. Amin. "Kindness to a Non-Muslim Neighbor: Tips for Interaction". Society. Islam Online. Archived from the original on 2005-08-28. Retrieved 2005-11-22.
Keltner, Dacher; DiSalvo, David (January 2017). "Forget Survival of the Fittest: It Is Kindness That Counts". Scientific American. A psychologist probes how altruism, Darwinism, and neurobiology mean that we can succeed by not being cutthroat.
External links
Wikimedia Commons has media related to Kindness.
Wikiquote has quotations related to Kindness.
The dictionary definition of kindness at Wiktionary
A UK independent, not-for-profit organisation
Random Acts of Kindness Foundation
Video with quotes about Kindness, from Wikiquote
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Seven virtues in Christian ethics
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E
In psychology, emotional detachment, also known as emotional blunting, is a condition or state in which a person lacks emotional connectivity to others, whether due to an unwanted circumstance or as a positive means to cope with anxiety. Such a coping strategy, also known as emotion-focused coping, is used when avoiding certain situations that might trigger anxiety.[3] It refers to the evasion of emotional connections. Emotional detachment may be a temporary reaction to a stressful situation, or a chronic condition such as depersonalization-derealization disorder. It may also be caused by certain antidepressants. Emotional blunting, also known as reduced affect display, is one of the negative symptoms of schizophrenia.
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Signs and symptoms
Emotional detachment may not be as outwardly obvious as other psychiatric symptoms. Patients diagnosed with emotional detachment have reduced ability to express emotion, to empathize with others or to form powerful emotional connections.[4] Patients are also at an increased risk for many anxiety and stress disorders. This can lead to difficulties in creating and maintaining personal relationships. The person may move elsewhere in their mind and appear preoccupied or "not entirely present", or they may seem fully present but exhibit purely intellectual behavior when emotional behavior would be appropriate. They may have a hard time being a loving family member, or they may avoid activities, places, and people associated with past traumas. Their dissociation can lead to lack of attention and, hence, to memory problems and in extreme cases, amnesia. In some cases, they present an extreme difficulty in giving or receiving empathy which can be related to the spectrum of narcissistic personality disorder.[5] Additionally, emotional blunting is negatively correlated with remission quality. The negative symptoms are far less likely to disappear when a patient is experiencing emotional blunting.[6]
In a study of children ages 4–12, traits of aggression and antisocial behaviors were found to be correlated with emotional detachment. Researchers determined that these could be early signs of emotional detachment, suggesting parents and clinicians to evaluate children with these traits for a higher behavioral problem in order to avoid bigger problems (such as emotional detachment) in the future.[7]
A correlation was found of higher emotional blunting among patients treated with depression who scored higher on the Hospital Anxiety and Depression Scale (HADS) and were male (though the frequency difference was slight).[6]
Emotional detachment in small amounts is normal. For example, being able to emotionally and psychologically detach from work when one is not in the workplace is a normal behavior. Emotional detachment becomes an issue when it impairs a person's ability to function on a day-to-day level.[8]
Scales
While some depression severity scales provide insight to emotional blunting levels, many symptoms are not adequately covered.[9] An attempt to resolve this issue is the Oxford Depression Questionnaire (ODQ), a scale specifically designed for full assessment of emotional blunting symptoms. The ODQ is designed specifically for patients with Major Depressive Disorder (MDD) in order to assess individual levels of emotional blunting.
Another scale, known as the Oxford Questionnaire on the Emotional Side-Effects of Antidepressants (OQESA), was developed using qualitative methods.[6]
Causes
Emotional detachment and/or emotional blunting have multiple causes, as the cause can vary from person to person. Emotional detachment or emotional blunting often arises due to adverse childhood experiences, for example physical, sexual or emotional abuse. Emotional detachment is a maladaptive coping mechanism for trauma, especially in young children who have not developed coping mechanisms. Emotional detachments can also be due to psychological trauma in adulthood, like abuse, or traumatic experiences like war, automobile accidents etc.[10][11]
Emotional blunting is often caused by antidepressants, in particular selective serotonin reuptake inhibitors (SSRIs) used in MDD and often as an add-on treatment in other psychiatric disorders.[12][13] Individuals with MDD usually experience emotional blunting as well.[9] Emotional blunting is a symptom of MDD,[6] as depression is negatively correlated with emotional (both positive and negative) experiences.[14]
Schizophrenia often occurs with negative symptoms, extrapyramidal signs (EPS), and depression. The latter overlaps with emotional blunting and is shown to be a core part of the present effects.[15] Schizophrenia in general causes abnormalities in emotional understanding of individuals, all of which are clinically considered as an emotional blunting symptom. Individuals with schizophrenia show less emotional experiences, display less emotional expressions, and fail to recognize the emotional experiences and/or expressions of other individuals.[16]
The changes in fronto-limbic activity in conjunction with depression succeeding a left hemisphere basal ganglia stroke (LBG stroke) may contribute to emotional blunting. LBG strokes are associated with depression and often caused by disorders of the basal ganglia (BG). Such disorders alter the emotional perception and experiences of the patient.[14]
In many cases people with eating disorders (ED) show signs of emotional detachment. This is due to the fact that many of the circumstances that often lead to an ED are the same as the circumstances that lead to emotional detachment. For example, people with ED often have experienced childhood abuse. Eating disorders on their own are a maladaptive coping mechanism and to cope with the effects of an eating disorder, people may turn to emotional detachment.[17]
Bereavement or losing a loved one can also be causes of emotional detachment.[17]
Unfortunately, the prevalence of emotional blunting is not fully known.[6]
Behavioral mechanism
Emotional detachment is a maladaptive coping mechanism, which allows a person to react calmly to highly emotional circumstances. Emotional detachment in this sense is a decision to avoid engaging emotional connections, rather than an inability or difficulty in doing so, typically for personal, social, or other reasons. In this sense it can allow people to maintain boundaries, and avoid undesired impact by or upon others, related to emotional demands. As such it is a deliberate mental attitude which avoids engaging the emotions of others.
This detachment does not necessarily mean avoiding empathy; rather, it allows the person to rationally choose whether or not to be overwhelmed or manipulated by such feelings. Examples where this is used in a positive sense might include emotional boundary management, where a person avoids emotional levels of engagement related to people who are in some way emotionally overly demanding, such as difficult co-workers or relatives, or is adopted to aid the person in helping others.
Emotional detachment can also be "emotional numbing",[18] "emotional blunting", i.e., dissociation, depersonalization or in its chronic form depersonalization disorder.[19] This type of emotional numbing or blunting is a disconnection from emotion, it is frequently used as a coping survival skill during traumatic childhood events such as abuse or severe neglect. After continually using this coping mechanism, it can become a response to daily stresses.[20]
Emotional detachment may allow acts of extreme cruelty and abuse, supported by the decision to not connect empathically with the person concerned. Social ostracism, such as shunning and parental alienation, are other examples where decisions to shut out a person creates a psychological trauma for the shunned party.[21]
See also
Psychology portal
Alexithymia
Anhedonia § Social anhedonia
Asociality
Assertiveness
Borderline Personality Disorder
Dissociation
Dissociative disorders (in DSM-IV)
Emotional contagion
Emotional dysregulation
Emotional isolation
Psychic distance
Reactive attachment disorder
Social rejection
Splitting (psychology)
Stoicism
Structured Clinical Interview for DSM-IV
References
Aarkrog T (1990). Edvard Munch: The Life of a Person with Borderline Personality as Seen Through His Art [Edvard Munch, et livsløb af en grænsepersonlighed forstået gennem hans billeder]. Danmark: Lundbeck Pharma A/S. ISBN 978-8798352419.
Wylie HW (1980). "Edvard Munch". The American Imago; A Psychoanalytic Journal for the Arts and Sciences. 37 (4). Johns Hopkins University Press: 413–443. JSTOR 26303797. PMID 7008567.
"Emotion-focused coping". APA Dictionary of Psychology. Washington, DC: American Psychological Association. n.d.
Dresden, Danielle (27 May 2020). "Emotional detachment: Symptoms, causes, and treatment". www.medicalnewstoday.com. Retrieved 8 January 2024.
Johnson, Stephen M (1987), Humanizing the Narcissistic Style, NY: Norton and Co., p. 125, ISBN 0-393-70037-2
Goodwin, G.M.; Price, J.; De Bodinat, C.; Laredo, J. (2017). "Emotional blunting with antidepressant treatments: A survey among depressed patients". Journal of Affective Disorders. 221. Elsevier BV: 31–35. doi:10.1016/j.jad.2017.05.048. ISSN 0165-0327. PMID 28628765. S2CID 3755520. Retrieved 2021-11-20.
Manti, Eirini; Scholte, Evert M.; Van Berckelaer-Onnes, Ina A.; Van Der Ploeg, Jan D. (2009). "Social and emotional detachment: A cross-cultural comparison of the non-disruptive behavioural psychopathic traits in children". Criminal Behaviour and Mental Health. 19 (3): 178–192. doi:10.1002/cbm.732. PMID 19475645.
Haun, Verena C.; Nübold, Annika; Bauer, Anna G. (2018-01-07). "Being mindful at work and at home: Buffering effects in the stressor-detachment model". Journal of Occupational and Organizational Psychology. 91 (2): 385–410. doi:10.1111/joop.12200. ISSN 0963-1798. S2CID 149204708.
Christensen, Michael Cronquist; Fagiolini, Andrea; Florea, Ioana; Loft, Henrik; Cuomo, Alessandro; Goodwin, Guy M. (November 2021). "Validation of the Oxford Depression Questionnaire: Sensitivity to change, minimal clinically important difference, and response threshold for the assessment of emotional blunting". Journal of Affective Disorders. 294: 924–931. doi:10.1016/j.jad.2021.07.099. ISSN 0165-0327. PMID 34378539.
Dell, Paul F.; O'Neil, John A., eds. (2010-11-01), "Chapter The Theory of Trauma-Related Structural Dissociation of the Personality", Dissociation and the Dissociative Disorders, Routledge, pp. 273–292, doi:10.4324/9780203893920, ISBN 978-0-203-89392-0
Foa, Edna B.; Hearst-Ikeda, Diana (1996), Michelson, Larry K.; Ray, William J. (eds.), "Emotional Dissociation in Response to Trauma", Handbook of Dissociation: Theor
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth creates pressure, absorbs most meteoroids and ultraviolet solar radiation, warms the surface through heat retention (greenhouse effect), and reduces temperature extremes between day and night (the diurnal temperature variation), maintaining conditions allowing life and liquid water to exist on the Earth's surface.
By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.03% carbon dioxide, and small amounts of other gases.[2] Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere.[3]
Earth's early atmosphere consisted of gases in the solar nebula, primarily hydrogen. The atmosphere changed significantly over time, affected by many factors such as volcanism, life, and weathering. Recently, human activity has also contributed to atmospheric changes, such as global warming, ozone depletion and acid deposition.
The atmosphere has a mass of about 5.15×1018 kg,[4] three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km (62 mi) or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.
The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann.[5] The study of historic atmosphere is called paleoclimatology.
Composition
Main article: Atmospheric chemistry
Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere (0.0442% at August 2021 concentrations[6][7]). Numbers are mainly from 2000, with CO2 and methane from 2019, and do not represent any single source.[8]
The three major constituents of Earth's atmosphere are nitrogen, oxygen, and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by mole fraction in the coldest portions of the atmosphere to as much as 5% by mole fraction in hot, humid air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor).[9]: 8 The remaining gases are often referred to as trace gases,[10] among which are other greenhouse gases, principally carbon dioxide, methane, nitrous oxide, and ozone. Besides argon, already mentioned, other noble gases, neon, helium, krypton, and xenon are also present. Filtered air includes trace amounts of many other chemical compounds. Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores, sea spray, and volcanic ash. Various industrial pollutants also may be present as gases or aerosols, such as chlorine (elemental or in compounds), fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide (SO2) may be derived from natural sources or from industrial air pollution.
The volume fraction of the main constituents of the Earth's atmosphere as a function of height, based on the MSIS-E-90 atmospheric model; the model only works above 85 km
Major constituents of air, by mole fraction[13]
Dry air
Gas Mole fraction(A)
Name Formula in ppm(B) in %
Nitrogen N2 780,840 78.084
Oxygen O2 209,460 20.946
Argon Ar 9,340 0.9340
Carbon dioxide
(April 2022)(C)[14] CO2 417 0.0417
Neon Ne 18.18 0.001818
Helium He 5.24 0.000524
Methane
(2022)(C)[15] CH4 1.91 0.000191
Krypton Kr 1.14 0.000114
If air is not dry:
Water vapor(D) H2O 0–30,000(D) 0–3%(E)
notes:
(A) Mole fraction is sometimes referred to as volume fraction; these are identical for an ideal gas only.
(B) ppm: parts per million by molecular count
The total ppm above adds up to more than 1 million (currently 83.43 above it) due to experimental error.
(C) The concentration of CO2 has been increasing in recent decades, as has that of CH4.
(D) Water vapor is about 0.25% by mass over full atmosphere
(E) Water vapor varies significantly locally[9]
The average molecular weight of dry air, which can be used to calculate densities or to convert between mole fraction and mass fraction, is about 28.946[16] or 28.96[17][18] g/mol. This is decreased when the air is humid.
The relative concentration of gases remains constant until about 10,000 m (33,000 ft).[19]
Stratification
Earth's atmosphere. Lower four layers of the atmosphere in three dimensions as seen diagonally from above the exobase. Layers drawn to scale, objects within the layers are not to scale. Aurorae shown at the bottom of the thermosphere can form at any altitude within this layer.
In general, air pressure and density decrease with altitude in the atmosphere. However, the temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions (see the temperature section). Because the general pattern of the temperature/altitude profile, or lapse rate, is constant and measurable by means of instrumented balloon soundings, the temperature behavior provides a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be divided (called atmospheric stratification) into five main layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.[20] The altitudes of the five layers are:
Exosphere: 700 to 10,000 km (440 to 6,200 miles)[21]
Thermosphere: 80 to 700 km (50 to 440 miles)[22]
Mesosphere: 50 to 80 km (31 to 50 miles)
Stratosphere: 12 to 50 km (7 to 31 miles)
Troposphere: 0 to 12 km (0 to 7 miles)[23]
Exosphere
Main article: Exosphere
The exosphere is the outermost layer of Earth's atmosphere (though it is so tenuous that some scientists consider it to be part of interplanetary space rather than part of the atmosphere). It extends from the thermopause (also known as the "exobase") at the top of the thermosphere to a poorly defined boundary with the solar wind and interplanetary medium. The altitude of the exobase varies from about 500 kilometres (310 mi; 1,600,000 ft) to about 1,000 kilometres (620 mi) in times of higher incoming solar radiation.[24]
The upper limit varies depending on the definition. Various authorities consider it to end at about 10,000 kilometres (6,200 mi)[25] or about 190,000 kilometres (120,000 mi)—about halfway to the moon, where the influence of Earth's gravity is about the same as radiation pressure from sunlight.[24] The geocorona visible in the far ultraviolet (caused by neutral hydrogen) extends to at least 100,000 kilometres (62,000 mi).[24]
This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase. The atoms and molecules are so far apart that they can travel hundreds of kilometres without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind. Every second, the Earth loses about 3 kg of hydrogen, 50 g of helium, and much smaller amounts of other constituents.[26]
The exosphere is too far above Earth for meteorological phenomena to be possible. However, Earth's auroras—the aurora borealis (northern lights) and aurora australis (southern lights)—sometimes occur in the lower part of the exosphere, where they overlap into the thermosphere. The exosphere contains many of the artificial satellites that orbit Earth.
Thermosphere
Main article: Thermosphere
The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause (which separates it from the mesosphere) at an altitude of about 80 km (50 mi; 260,000 ft) up to the thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft). The height of the thermopause varies considerably due to changes in solar activity.[22] Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase. The lower part of the thermosphere, from 80 to 550 kilometres (50 to 342 mi) above Earth's surface, contains the ionosphere.
The temperature of the thermosphere gradually increases with height and can rise as high as 1500 °C (2700 °F), though the gas molecules are so far apart that its temperature in the usual sense is not very meaningful. The air is so rarefied that an individual molecule (of oxygen, for example) travels an average of 1 kilometre (0.62 mi; 3300 ft) between collisions with other molecules.[27] Although the thermosphere has a high proportion of molecules with high energy, it would not feel hot to a human in direct contact, because its density is too low to conduct a significant amount of energy to or from the skin.
This layer is completely cloudless and free of water vapor. However, non-hydrometeorological phenomena such as the aurora borealis and aurora australis are occasionally seen in the thermosphere. The International Space Station orbits in this layer, between 350 and 420 km (220 and 260 mi). It is this layer where many of the satellites orbiting the Earth are present.
Mesosphere
Main article: Mesosphere
Afterglow of the troposphere (orange), the stratosphere (blue) and the mesosphere (dark) at which atmospheric entry begins, leaving smoke trails, such as in this case of a spacecraft reentry
The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere. It extends from the stratopause at an altitude of about 50 km (31 mi; 160,000 ft) to the mesopause at 80–85 km (50–53 mi; 260,000–280,000 ft) above sea level.
Temperatures drop with increasing altitude to the mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F; 190 K).[28][29]
Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can condense into polar-mesospheric noctilucent clouds of ice particles. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or similarly before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds. The mesosphere is also the layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft.
components. Most structural proteins are fibrous proteins; for example, collagen and elastin are critical components of connective tissue such as cartilage, and keratin is found in hard or filamentous structures such as hair, nails, feathers, hooves, and some animal shells.[34]: 178–81 Some globular proteins can also play structural functions, for example, actin and tubulin are globular and soluble as monomers, but polymerize to form long, stiff fibers that make up the cytoskeleton, which allows the cell to maintain its shape and size.
Other proteins that serve structural functions are motor proteins such as myosin, kinesin, and dynein, which are capable of generating mechanical forces. These proteins are crucial for cellular motility of single celled organisms and the sperm of many multicellular organisms which reproduce sexually. They also generate the forces exerted by contracting muscles[34]: 258–64, 272 and play essential roles in intracellular transport.
Protein evolution
Main article: Molecular evolution
A key question in molecular biology is how proteins evolve, i.e. how can mutations (or rather changes in amino acid sequence) lead to new structures and functions? Most amino acids in a protein can be changed without disrupting activity or function, as can be seen from numerous homologous proteins across species (as collected in specialized databases for protein families, e.g. PFAM).[56] In order to prevent dramatic consequences of mutations, a gene may be duplicated before it can mutate freely. However, this can also lead to complete loss of gene function and thus pseudo-genes.[57] More commonly, single amino acid changes have limited consequences although some can change protein function substantially, especially in enzymes. For instance, many enzymes can change their substrate specificity by one or a few mutations.[58] Changes in substrate specificity are facilitated by substrate promiscuity, i.e. the ability of many enzymes to bind and process multiple substrates. When mutations occur, the specificity of an enzyme can increase (or decrease) and thus its enzymatic activity.[58] Thus, bacteria (or other organisms) can adapt to different food sources, including unnatural substrates such as plastic.[59]
Methods of study
Main article: Protein methods
Methods commonly used to study protein structure and function include immunohistochemistry, site-directed mutagenesis, X-ray crystallography, nuclear magnetic resonance and mass spectrometry.
The activities and structures of proteins may be examined in vitro, in vivo, and in silico. In vitro studies of purified proteins in controlled environments are useful for learning how a protein carries out its function: for example, enzyme kinetics studies explore the chemical mechanism of an enzyme's catalytic activity and its relative affinity for various possible substrate molecules. By contrast, in vivo experiments can provide information about the physiological role of a protein in the context of a cell or even a whole organism. In silico studies use computational methods to study proteins.
Protein purification
Main article: Protein purification
Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation, precipitation, electrophoresis, and chromatography; the advent of genetic engineering has made possible a number of methods to facilitate purification.
To perform in vitro analysis, a protein must be purified away from other cellular components. This process usually begins with cell lysis, in which a cell's membrane is disrupted and its internal contents released into a solution known as a crude lysate. The resulting mixture can be purified using ultracentrifugation, which fractionates the various cellular components into fractions containing soluble proteins; membrane lipids and proteins; cellular organelles, and nucleic acids. Precipitation by a method known as salting out can concentrate the proteins from this lysate. Various types of chromatography are then used to isolate the protein or proteins of interest based on properties such as molecular weight, net charge and binding affinity.[30]: 21–24 The level of purification can be monitored using various types of gel electrophoresis if the desired protein's molecular weight and isoelectric point are known, by spectroscopy if the protein has distinguishable spectroscopic features, or by enzyme assays if the protein has enzymatic activity. Additionally, proteins can be isolated according to their charge using electrofocusing.[60]
For natural proteins, a series of purification steps may be necessary to obtain protein sufficiently pure for laboratory applications. To simplify this process, genetic engineering is often used to add chemical features to proteins that make them easier to purify without affecting their structure or activity. Here, a "tag" consisting of a specific amino acid sequence, often a series of histidine residues (a "His-tag"), is attached to one terminus of the protein. As a result, when the lysate is passed over a chromatography column containing nickel, the histidine residues ligate the nickel and attach to the column while the untagged components of the lysate pass unimpeded. A number of different tags have been developed to help researchers purify specific proteins from complex mixtures.[61]
Cellular localization
Proteins in different cellular compartments and structures tagged with green fluorescent protein (here, white)
The study of proteins in vivo is often concerned with the synthesis and localization of the protein within the cell. Although many intracellular proteins are synthesized in the cytoplasm and membrane-bound or secreted proteins in the endoplasmic reticulum, the specifics of how proteins are targeted to specific organelles or cellular structures is often unclear. A useful technique for assessing cellular localization uses genetic engineering to express in a cell a fusion protein or chimera consisting of the natural protein of interest linked to a "reporter" such as green fluorescent protein (GFP).[62] The fused protein's position within the cell can then be cleanly and efficiently visualized using microscopy,[63] as shown in the figure opposite.
Other methods for elucidating the cellular location of proteins requires the use of known compartmental markers for regions such as the ER, the Golgi, lysosomes or vacuoles, mitochondria, chloroplasts, plasma membrane, etc. With the use of fluorescently tagged versions of these markers or of antibodies to known markers, it becomes much simpler to identify the localization of a protein of interest. For example, indirect immunofluorescence will allow for fluorescence colocalization and demonstration of location. Fluorescent dyes are used to label cellular compartments for a similar purpose.[64]
Other possibilities exist, as well. For example, immunohistochemistry usually uses an antibody to one or more proteins of interest that are conjugated to enzymes yielding either luminescent or chromogenic signals that can be compared between samples, allowing for localization information. Another applicable technique is cofractionation in sucrose (or other material) gradients using isopycnic centrifugation.[65] While this technique does not prove colocalization of a compartment of known density and the protein of interest, it does increase the likelihood, and is more amenable to large-scale studies.
Finally, the gold-standard method of cellular localization is immunoelectron microscopy. This technique also uses an antibody to the protein of interest, along with classical electron microscopy techniques. The sample is prepared for normal electron microscopic examination, and then treated with an antibody to the protein of interest that is conjugated to an extremely electro-dense material, usually gold. This allows for the localization of both ultrastructural details as well as the protein of interest.[66]
Through another genetic engineering application known as site-directed mutagenesis, researchers can alter the protein sequence and hence its structure, cellular localization, and susceptibility to regulation. This technique even allows the incorporation of unnatural amino acids into proteins, using modified tRNAs,[67] and may allow the rational design of new proteins with novel properties.[68]
Proteomics
Main article: Proteomics
The total complement of proteins present at a time in a cell or cell type is known as its proteome, and the study of such large-scale data sets defines the field of proteomics, named by analogy to the related field of genomics. Key experimental techniques in proteomics include 2D electrophoresis,[69] which allows the separation of many proteins, mass spectrometry,[70] which allows rapid high-throughput identification of proteins and sequencing of peptides (most often after in-gel digestion), protein microarrays, which allow the detection of the relative levels of the various proteins present in a cell, and two-hybrid screening, which allows the systematic exploration of protein–protein interactions.[71] The total complement of biologically possible such interactions is known as the interactome.[72] A systematic attempt to determine the structures of proteins representing every possible fold is known as structural genomics.[73]
Structure determination
Discovering the tertiary structure of a protein, or the quaternary structure of its complexes, can provide important clues about how the protein performs its function and how it can be affected, i.e. in drug design. As proteins are too small to be seen under a light microscope, other methods have to be employed to determine their structure. Common experimental methods include X-ray crystallography and NMR spectroscopy, both of which can produce structural information at atomic resolution. However, NMR experiments are able to provide information from which a subset of distances between pairs of atoms can be estimated, and the final possible conformations for a protein are determined by solving a distance geometry problem. Dual polarisation interferometry is a quantitative analytical method for measuring the overall protein conformation and conformational changes due to interactions or other stimulus. Circular dichroism is another laboratory technique for determining internal β-sheet / α-helical composition of proteins. Cryoelectron microscopy is used to produce lower-resolution structural information about very large protein complexes, including assembled viruses;[33]: 340–41 a variant known as electron crystallography can also produce high-resolution information in some cases, especially for two-dimensional crystals of membrane proteins.[74] Solved structures are usually deposited in the Protein Data Bank (PDB), a freely available resource from which structural data about thousands of proteins can be obtained in the form of Cartesian coordinates for each atom in the protein.[75]
Many more gene sequences are known than protein structures. Further, the set of solved structures is biased toward proteins that can be easily subjected to the conditions required in X-ray crystallography, one of the major structure determination methods. In particular, globular proteins are comparatively easy to crystallize in preparation for X-ray crystallography. Membrane proteins and large protein complexes, by contrast, are difficult to crystallize and are underrepresented in the PDB.[76] Structural genomics initiatives have attempted to remedy these deficiencies by systematically solving representative structures of major fold classes. Protein structure prediction methods attempt to provide a means of generating a plausible structure for proteins whose structures have not been experimentally determined.[77]
Structure prediction
Constituent amino-acids can be analyzed to predict secondary, tertiary and quaternary protein structure, in this case hemoglobin containing heme units
Main articles: Protein structure prediction and List of protein structure prediction software
Complementary to the field of structural genomics, protein structure prediction develops efficient mathematical models of proteins to computationally predict the molecular formations in theory, instead of detecting structures with laboratory observation.[78] The most successful type of structure prediction, known as homology modeling, relies on the existence of a "template" structure with sequence similarity to the protein being modeled; structural genomics' goal is to provide sufficient representation in solved structures to model most of those that remain.[79] Although producing accurate models remains a challenge when only distantly related template structures are available, it has been suggested that sequence alignment is the bottleneck in this process, as quite accurate models can be produced if a "perfect" sequence alignment is known.[80] Many structure prediction methods have served to inform the emerging field of protein engineering, in which novel protein folds have already been designed.[81] Also proteins (in eukaryotes ~33%) contain large unstructured but biologically functional segments and can be classified as intrinsically disordered proteins.[82] Predicting and analysing protein disorder is, therefore, an important part of protein structure characterisation.[83]
Bioinformatics
Main article: Bioinformatics
A vast array of computational methods have been developed to analyze the structure, function and evolution of proteins. The development of such tools has been driven by the large amount of genomic and proteomic data available for a variety of organisms, including the human genome. It is simply impossible to study all proteins experimentally, hence only a few are subjected to laboratory experiments while computational tools are used to extrapolate to similar proteins. Such homologous proteins can be efficiently identified in distantly related organisms by sequence alignment. Genome and gene sequences can be searched by a variety of tools for certain properties. Sequence profiling tools can find restriction enzyme sites, open reading frames in nucleotide sequences, and predict secondary structures. Phylogenetic trees can be constructed and evolutionary hypotheses developed using special software like ClustalW regarding the ancestry of modern organisms and the genes they express. The field of bioinformatics is now indispensable for the analysis of genes and proteins.
In silico simulation of dynamical processes
A more complex computational problem is the prediction of intermolecular interactions, such as in molecular docking,[84] protein folding, protein–protein interaction and chemical reactivity. Mathematical models to simulate these dynamical processes involve molecular mechanics, in particular, molecular dynamics. In this regard, in silico simulations discovered the folding of small α-helical protein domains such as the villin headpiece,[85] the HIV accessory protein[86] and hybrid methods combining standard molecular dynamics with quantum mechanical mathematics have explored the electronic states of rhodopsins.[87]
Beyond classical molecular dynamics, quantum dynamics methods allow the simulation of proteins in atomistic detail with an accurate description of quantum mechanical effects. Examples include the multi-layer multi-configuration time-dependent Hartree (MCTDH) method and the hierarchical equations of motion (HEOM) approach, which have been applied to plant cryptochromes[88] and bacteria light-harvesting complexes,[89] respectively. Both quantum and classical mechanical simulations of biological-scale systems are extremely computationally demanding, so distributed computing initiatives (for example, the Folding@home project[90]) facilitate the molecular modeling by exploiting advances in GPU parallel processing and Monte Carlo techniques.
Chemical analysis
The total nitrogen content of organic matter is mainly formed by the amino groups in proteins. The Total Kjeldahl Nitrogen (TKN) is a measure of nitrogen widely used in the analysis of (waste) water, soil, food, feed and organic matter in general. As the name suggests, the Kjeldahl method is applied. More sensitive methods are available.[91][92]
Nutrition
Further information: Protein (nutrient) and Protein quality
Most microorganisms and plants can biosynthesize all 20 standard amino acids, while animals (including humans) must obtain some of the amino acids from the diet.[47] The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids. Key enzymes that synthesize certain amino acids are not present in animals—such as aspartokinase, which catalyses the first step in the synthesis of lysine, methionine, and threonine from aspartate. If amino acids are present in the environment, microorganisms can conserve energy by taking up the amino acids from their surroundings and downregulating their biosynthetic pathways.
In animals, amino acids are obtained through the consumption of foods containing protein. Ingested proteins are then broken down into amino acids through digestion, which typically involves denaturation of the protein through exposure to acid and hydrolysis by enzymes called proteases. Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. This use of protein as a fuel is particularly important under starvation conditions as it allows the body's own proteins to be used to support life, particularly those found in muscle.[93]
In animals such as dogs and cats, protein maintains the health and quality of the skin by promoting hair follicle growth and keratinization, and thus reducing the likelihood of skin problems producing malodours.[94] Poor-quality proteins also have a role regarding gastrointestinal health, increasing the potential for flatulence and odorous compounds in dogs because when proteins reach the colon in an undigested state, they are fermented producing hydrogen sulfide gas, indole, and skatole.[95] Dogs and cats digest animal proteins better than those from plants, but products of low-quality animal origin are poorly digested, including skin, feathers, and connective tissue.[95]
Mechanical Properties
The mechanical properties of proteins are highly diverse and are often central to their biological function, as in the case of proteins like keratin and collagen.[96] For instance, the ability of muscle tissue to continually expand and contract is directly tied to the elastic properties of their underlying protein makeup.[97][98] Beyond fibrous proteins, the conformational dynamics of enzymes[99] and the structure of biological membranes, among other biological functions, are governed by the mechanical properties of the proteins. Outside of their biological context, the unique mechanical properties of many proteins, along with their relative sustainability when compared to synthetic polymers, have made them desirable targets for next-generation materials design.[100][101]
Young's Modulus
Young's modulus, E, is calculated as the axial stress σ over the resulting strain ε. It is a measure of the relative stiffness of a material. In the context of proteins, this stiffness often directly correlates to biological function. For example, collagen, found in connective tissue, bones, and cartilage, and keratin, found in nails, claws, and hair, have observed stiffnesses that are several orders of magnitude higher than that of elastin,[102] which is though to give elasticity to structures such as blood vessels, pulmonary tissue, and bladder tissue, among others.[103][104] In comparison to this, globular proteins, such as Bovine Serum Albumin, which float relatively freely in the cytosol and often function as enzymes (and thus undergoing frequent conformational changes) have comparably much lower Young's moduli.[105][106]
The Young's modulus of a single protein can be found through molecular dynamics simulation. Using either atomistic force-fields, such as CHARMM or GROMOS, or coarse-grained forcefields like Martini,[107] a single protein molecule can be stretched by a uniaxial force while the resulting extension is recorded in order to calculate the strain.[108][109] Experimentally, methods such as atomic force microscopy can be used to obtain similar data.[110]
At the macroscopic level, the Young's modulus of cross-linked protein networks can be obtained through more traditional mechanical testing. Experimentally observed values for a few proteins can be seen below.
Elasticity of Various Proteins
Protein Protein Class Young's modulus
Keratin (Cross-Linked) Fibrous 1.5-10 GPa[111]
Elastin (Cross-Linked) Fibrous 1 MPa[102]
Fibrin (Cross-linked) Fibrous 1-10 MPa [102]
Collagen (Cross-linked) Fibrous 5-7.5 GPa[102][112]
Resilin (Cross-Linked) Fibrous 1-2 MPa[102]
Bovine Serum Albumin (Cross-Linked) Globular 2.5-15 KPa[105]
β-Barrel Outer Membrane Proteins Membrane 20-45 GPa[113]
Viscosity
In addition to serving as enzymes within the cell, globular proteins often act as key transport molecules. For instance, Serum Albumins, a key component of blood, are necessary for the transport of a multitude of small molecules throughout the body.[114] Because of this, the concentration dependent behavior of these proteins in solution is directly tied to the function of the circulatory system. On way of quantifying this behavior is through the viscosity of the solution.
Viscosity, η, is generally given is a measure of a fluid's resistance to deformation. It can be calculated as the ratio between the applied stress and the rate of change of the resulting shear strain, that is, the rate of deformation. Viscosity of complex liquid mixtures, such as blood, often depends strongly on temperature and solute concentration.[115] For serum albumin, specifically bovine serum albumin, the following relation between viscosity and temperature and concentration can be used.[116]
�
=
exp
[
�
�
−
�
�
(
−
�
+
�
�
+
Δ
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{\displaystyle \eta =\exp \left[{\frac {c}{\alpha -\beta \ c}}\left(-B+DT+{\frac {\Delta E}{RT}}\right)\right]}
Where c is the concentration, T is the temperature, R is the gas constant, and α, β, B, D, and ΔE are all material-based property constants. This equation has the form of an Arrhenius equation, assigning viscosity an exponential dependence on temperature and concentration.
See also
Deproteination
DNA-binding protein
Macromolecule
Index of protein-related articles
Intein
List of proteins
Proteopathy
Proteopedia
Proteolysis
Protein sequence space
Protein superfamily
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Further reading
Textbooks
Branden C, Tooze J (1999). Introduction to Protein Structure. New York: Garland Pub. ISBN 978-0-8153-2305-1.
Murray RF, Harper HW, Granner DK, Mayes PA, Rodwell VW (2006). Harper's Illustrated Biochemistry. New York: Lange Medical Books/McGraw-Hill. ISBN 978-0-07-146197-9.
Van Holde KE, Mathews CK (1996). Biochemistry. Menlo Park, California: Benjamin/Cummings Pub. Co., Inc. ISBN 978-0-8053-3931-4.
External links
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Folding@Home (Stanford University) Archived 2012-09-08 at the Wayback Machine
Protein Databank in Europe (see also PDBeQuips, short articles and tutorials on interesting PDB structures)
Research Collaboratory for Structural Bioinformatics (see also Molecule of the Month Archived 2020-07-24 at the Wayback Machine, presenting short accounts on selected proteins from the PDB)
Proteopedia – Life in 3D: rotatable, zoomable 3D model with wiki annotations for every known protein molecular structure.
UniProt the Universal Protein Resource
Tutorials and educational websites
"An Introduction to Proteins" from HOPES (Huntington's Disease Outreach Project for Education at Stanford)
Proteins: Biogenesis to Degradation – The Virtual Library of Biochemistry and Cell Biology
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In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.[1]
The term often refers specifically to triglycerides (triple esters of glycerol), that are the main components of vegetable oils and of fatty tissue in animals;[2] or, even more narrowly, to triglycerides that are solid or semisolid at room temperature, thus excluding oils. The term may also be used more broadly as a synonym of lipid—any substance of biological relevance, composed of carbon, hydrogen, or oxygen, that is insoluble in water but soluble in non-polar solvents.[1] In this sense, besides the triglycerides, the term would include several other types of compounds like mono- and diglycerides, phospholipids (such as lecithin), sterols (such as cholesterol), waxes (such as beeswax),[1] and free fatty acids, which are usually present in human diet in smaller amounts.[2]
Fats are one of the three main macronutrient groups in human diet, along with carbohydrates and proteins,[1][3] and the main components of common food products like milk, butter, tallow, lard, salt pork, and cooking oils. They are a major and dense source of food energy for many animals and play important structural and metabolic functions in most living beings, including energy storage, waterproofing, and thermal insulation.[4] The human body can produce the fat it requires from other food ingredients, except for a few essential fatty acids that must be included in the diet. Dietary fats are also the carriers of some flavor and aroma ingredients and vitamins that are not water-soluble.[2]
Biological importance
In humans and many animals, fats serve both as energy sources and as stores for energy in excess of what the body needs immediately. Each gram of fat when burned or metabolized releases about 9 food calories (37 kJ = 8.8 kcal).[5]
Fats are also sources of essential fatty acids, an important dietary requirement. Vitamins A, D, E, and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats.
Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. Fat also serves as a useful buffer against a host of diseases. When a particular substance, whether chemical or biotic, reaches unsafe levels in the bloodstream, the body can effectively dilute—or at least maintain equilibrium of—the offending substances by storing it in new fat tissue.[6] This helps to protect vital organs, until such time as the offending substances can be metabolized or removed from the body by such means as excretion, urination, accidental or intentional bloodletting, sebum excretion, and hair growth.
Adipose tissue
The obese mouse on the left has large stores of adipose tissue. For comparison, a mouse with a normal amount of adipose tissue is shown on the right.
In animals, adipose tissue, or fatty tissue is the body's means of storing metabolic energy over extended periods of time. Adipocytes (fat cells) store fat derived from the diet and from liver metabolism. Under energy stress these cells may degrade their stored fat to supply fatty acids and also glycerol to the circulation. These metabolic activities are regulated by several hormones (e.g., insulin, glucagon and epinephrine). Adipose tissue also secretes the hormone leptin.[7]
Production and processing
A variety of chemical and physical techniques are used for the production and processing of fats, both industrially and in cottage or home settings. They include:
Pressing to extract liquid fats from fruits, seeds, or algae, e.g. olive oil from olives
Solvent extraction using solvents like hexane or supercritical carbon dioxide
Rendering, the melting of fat in adipose tissue, e.g. to produce tallow, lard, fish oil, and whale oil
Churning of milk to produce butter
Hydrogenation to increase the degree of saturation of the fatty acids
Interesterification, the rearrangement of fatty acids across different triglycerides
Winterization to remove oil components with higher melting points
Clarification of butter
Metabolism
See also: Fatty acid metabolism
The pancreatic lipase acts at the ester bond, hydrolyzing the bond and "releasing" the fatty acid. In triglyceride form, lipids cannot be absorbed by the duodenum. Fatty acids, monoglycerides (one glycerol, one fatty acid), and some diglycerides are absorbed by the duodenum, once the triglycerides have been broken down.
In the intestine, following the secretion of lipases and bile, triglycerides are split into monoacylglycerol and free fatty acids in a process called lipolysis. They are subsequently moved to absorptive enterocyte cells lining the intestines. The triglycerides are rebuilt in the enterocytes from their fragments and packaged together with cholesterol and proteins to form chylomicrons. These are excreted from the cells and collected by the lymph system and transported to the large vessels near the heart before being mixed into the blood. Various tissues can capture the chylomicrons, releasing the triglycerides to be used as a source of energy. Liver cells can synthesize and store triglycerides. When the body requires fatty acids as an energy source, the hormone glucagon signals the breakdown of the triglycerides by hormone-sensitive lipase to release free fatty acids. As the brain cannot utilize fatty acids as an energy source (unless converted to a ketone),[8] the glycerol component of triglycerides can be converted into glucose, via gluconeogenesis by conversion into dihydroxyacetone phosphate and then into glyceraldehyde 3-phosphate, for brain fuel when it is broken down. Fat cells may also be broken down for that reason if the brain's needs ever outweigh the body's.
Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol. Fatty acids can then be taken up by cells via fatty acid transport proteins (FATPs).
Triglycerides, as major components of very-low-density lipoprotein (VLDL) and chylomicrons, play an important role in metabolism as energy sources and transporters of dietary fat. They contain more than twice as much energy (approximately 9 kcal/g or 38 kJ/g) as carbohydrates (approximately 4 kcal/g or 17 kJ/g).[9]
Nutritional and health aspects
The most common type of fat, in human diet and most living beings, is a triglyceride, an ester of the triple alcohol glycerol H(–CHOH–)
3H and three fatty acids. The molecule of a triglyceride can be described as resulting from a condensation reaction (specifically, esterification) between each of glycerol's –OH groups and the HO– part of the carboxyl group HO(O=)C− of each fatty acid, forming an ester bridge −O−(O=)C− with elimination of a water molecule H
2O.
Other less common types of fats include diglycerides and monoglycerides, where the esterification is limited to two or just one of glycerol's –OH groups. Other alcohols, such as cetyl alcohol (predominant in spermaceti), may replace glycerol. In the phospholipids, one of the fatty acids is replaced by phosphoric acid or a monoester thereof. The benefits and risks of various amounts and types of dietary fats have been the object of much study, and are still highly controversial topics.[10][11][12][13]
Essential fatty acids
There are two essential fatty acids (EFAs) in human nutrition: alpha-Linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid).[14][5] The adult body can synthesize other lipids that it needs from these two.
Dietary sources
Properties of vegetable oils[15][16]
The nutritional values are expressed as percent (%) by mass of total fat.
Type Processing
treatment[17] Saturated
fatty acids Monounsaturated
fatty acids Polyunsaturated
fatty acids Smoke point
Total[15] Oleic
acid
(ω-9) Total[15] α-Linolenic
acid
(ω-3) Linoleic
acid
(ω-6) ω-6:3
ratio
Avocado[18] 11.6 70.6 52–66
[19] 13.5 1 12.5 12.5:1 250 °C (482 °F)[20]
Brazil nut[21] 24.8 32.7 31.3 42.0 0.1 41.9 419:1 208 °C (406 °F)[22]
Canola[23] 7.4 63.3 61.8 28.1 9.1 18.6 2:1 204 °C (400 °F)[24]
Coconut[25] 82.5 6.3 6 1.7 0.019 1.68 88:1 175 °C (347 °F)[22]
Corn[26] 12.9 27.6 27.3 54.7 1 58 58:1 232 °C (450 °F)[24]
Cottonseed[27] 25.9 17.8 19 51.9 1 54 54:1 216 °C (420 °F)[24]
Cottonseed[28] hydrogenated 93.6 1.5 0.6 0.2 0.3 1.5:1
Flaxseed/linseed[29] 9.0 18.4 18 67.8 53 13 0.2:1 107 °C (225 °F)
Grape seed 10.4 14.8 14.3 74.9 0.15 74.7 very high 216 °C (421 °F)[30]
Hemp seed[31] 7.0 9.0 9.0 82.0 22.0 54.0 2.5:1 166 °C (330 °F)[32]
High-oleic safflower oil[33] 7.5 75.2 75.2 12.8 0 12.8 very high 212 °C (414 °F)[22]
Olive, Extra Virgin[34] 13.8 73.0 71.3 10.5 0.7 9.8 14:1 193 °C (380 °F)[22]
Palm[35] 49.3 37.0 40 9.3 0.2 9.1 45.5:1 235 °C (455 °F)
Palm[36] hydrogenated 88.2 5.7 0
Peanut[37] 16.2 57.1 55.4 19.9 0.318 19.6 61.6:1 232 °C (450 °F)[24]
Rice bran oil 25 38.4 38.4 36.6 2.2 34.4[38] 15.6:1 232 °C (450 °F)[39]
Sesame[40] 14.2 39.7 39.3 41.7 0.3 41.3 138:1
Soybean[41] 15.6 22.8 22.6 57.7 7 51 7.3:1 238 °C (460 °F)[24]
Soybean[42] partially hydrogenated 14.9 43.0 42.5 37.6 2.6 34.9 13.4:1
Sunflower[43] 8.99 63.4 62.9 20.7 0.16 20.5 128:1 227 °C (440 °F)[24]
Walnut oil[44] unrefined 9.1 22.8 22.2 63.3 10.4 52.9 5:1 160 °C (320 °F)[45]
Saturated vs. unsaturated fats
Different foods contain different amounts of fat with different proportions of saturated and unsaturated fatty acids. Some animal products, like beef and dairy products made with whole or reduced fat milk like yogurt, ice cream, cheese and butter have mostly saturated fatty acids (and some have significant contents of dietary cholesterol). Other animal products, like pork, poultry, eggs, and seafood have mostly unsaturated fats. Industrialized baked goods may use fats with high unsaturated fat contents as well, especially those containing partially hydrogenated oils, and processed foods that are deep-fried in hydrogenated oil are high in saturated fat content.[46][47][48]
Plants and fish oil generally contain a higher proportion of unsaturated acids, although there are exceptions such as coconut oil and palm kernel oil.[49][50] Foods containing unsaturated fats include avocado, nuts, olive oils, and vegetable oils such as canola.
Many careful studies have found that replacing saturated fats with cis unsaturated fats in the diet reduces risk of cardiovascular diseases (CVDs),[51][52] diabetes, or death.[53] These studies prompted many medical organizations and public health departments, including the World Health Organization (WHO),[54][55] to officially issue that advice. Some countries with such recommendations include:
United Kingdom[56][57][58][59][60]
United States[53][61][62][63][64]
India[65][66]
Canada[67]
Australia[68]
Singapore[69]
New Zealand[70]
Hong Kong[71]
A 2004 review concluded that "no lower safe limit of specific saturated fatty acid intakes has been identified" and recommended that the influence of varying saturated fatty acid intakes against a background of different individual lifestyles and genetic backgrounds should be the focus in future studies.[72]
This advice is often oversimplified by labeling the two kinds of fats as bad fats and good fats, respectively. However, since the fats and oils in most natural and traditionally processed foods contain both unsaturated and saturated fatty acids,[73] the complete exclusion of saturated fat is unrealistic and possibly unwise. For instance, some foods rich in saturated fat, such as coconut and palm oil, are an important source of cheap dietary calories for a large fraction of the population in developing countries.[74]
Concerns were also expressed at a 2010 conference of the American Dietetic Association that a blanket recommendation to avoid saturated fats could drive people to also reduce the amount of polyunsaturated fats, which may have health benefits, and/or replace fats by refined carbohydrates — which carry a high risk of obesity and heart disease.[75]
For these reasons, the U.S. Food and Drug Administration, for example, recommends to consume at least 10% (7% for high-risk groups) of calories from saturated fat, with an average of 30% (or less) of total calories from all fat.[76][74] A general 7% limit was recommended also by the American Heart Association (AHA) in 2006.[77][78]
The WHO/FAO report also recommended replacing fats so as to reduce the content of myristic and palmitic acids, specifically.[74]
The so-called Mediterranean diet, prevalent in many countries in the Mediterranean Sea area, includes more total fat than the diet of Northern European countries, but most of it is in the form of unsaturated fatty acids (specifically, monounsaturated and omega-3) from olive oil and fish, vegetables, and certain meats like lamb, while consumption of saturated fat is minimal in comparison. A 2017 review found evidence that a Mediterranean-style diet could reduce the risk of cardiovascular diseases, overall cancer incidence, neurodegenerative diseases, diabetes, and mortality rate.[79] A 2018 review showed that a Mediterranean-like diet may improve overall health status, such as reduced risk of non-communicable diseases. It also may reduce the social and economic costs of diet-related illnesses.[80]
A small number of contemporary reviews have challenged this negative view of saturated fats. For example, an evaluation of evidence from 1966 to 1973 of the observed health impact of replacing dietary saturated fat with linoleic acid found that it increased rates of death from all causes, coronary heart disease, and cardiovascular disease.[81] These studies have been disputed by many scientists,[82] and the consensus in the medical community is that saturated fat and cardiovascular disease are closely related.[83][84][85] Still, these discordant studies fueled debate over the merits of substituting polyunsaturated fats for saturated fats.[86]
Cardiovascular disease
Main article: Saturated fat and cardiovascular disease
The effect of saturated fat on cardiovascular disease has been extensively studied.[87] The general consensus is that there is evidence of moderate-quality of a strong, consistent, and graded relationship between saturated fat intake, blood cholesterol levels, and the incidence of cardiovascular disease.[53][87] The relationships are accepted as causal,[88][89] including by many government and medical organizations.[74][90][91][53][92][93][94][95]
A 2017 review by the AHA estimated that replacement of saturated fat with polyunsaturated fat in the American diet could reduce the risk of cardiovascular diseases by 30%.[53]
The consumption of saturated fat is generally considered a risk factor for dyslipidemia—abnormal blood lipid levels, including high total cholesterol, high levels of triglycerides, high levels of low-density lipoprotein (LDL, "bad" cholesterol) or low levels of high-density lipoprotein (HDL, "good" cholesterol). These parameters in turn are believed to be risk indicators for some types of cardiovascular disease.[96][97][98][99][100][92][101][102][103] These effects were observed in children too.[104]
Several meta-analyses (reviews and consolidations of multiple previously published experimental studies) have confirmed a significant relationship between saturated fat and high serum cholesterol levels,[53][105] which in turn have been claimed to have a causal relation with increased risk of cardiovascular disease (the so-called lipid hypothesis).[106][107] However, high cholesterol may be caused by many factors. Other indicators, such as high LDL/HDL ratio, have proved to be more predictive.[107] In a study of myocardial infarction in 52 countries, the ApoB/ApoA1 (related to LDL and HDL, respectively) ratio was the strongest predictor of CVD among all risk factors.[108] There are other pathways involving obesity, triglyceride levels, insulin sensitivity, endothelial function, and thrombogenicity, among others, that play a role in CVD, although it seems, in the absence of an adverse blood lipid profile, the other known risk factors have only a weak atherogenic effect.[109] Different saturated fatty acids have differing effects on various lipid levels.[110]
Cancer
The evidence for a relation between saturated fat intake and cancer is significantly weaker, and there does not seem to be a clear medical consensus about it.
A meta-analysis published in 2003 found a significant positive relationship between saturated fat and breast cancer.[111] However two subsequent reviews have found weak or insignificant relation,[112][113] and noted the prevalence of confounding factors.[112][114]
Another review found limited evidence for a positive relationship between consuming animal fat and incidence of colorectal cancer.[115]
Other meta-analyses found evidence for increased risk of ovarian cancer by high consumption of saturated fat.[116]
Some studies have indicated that serum myristic acid[117][118] and palmitic acid[118] and dietary myristic[119] and palmitic[119] saturated fatty acids and serum palmitic combined with alpha-tocopherol supplementation[117] are associated with increased risk of prostate cancer in a dose-dependent manner. These associations may, however, reflect differences in intake or metabolism of these fatty acids between the precancer cases and controls, rather than being an actual cause.[118]
Bones
Various animal studies have indicated that the intake of saturated fat has a negative effect on the mineral density of bones. One study suggested that men may be particularly vulnerable.[120]
Disposition and overall health
Studies have shown that substituting monounsaturated fatty acids for saturated ones is associated with increased daily physical activity and resting energy expenditure. More physical activity, less anger, and less irritability were associated with a higher-oleic acid diet than one of a palmitic acid diet.[121]
Amounts of fat types in selected foods
Monounsaturated vs. polyunsaturated fat
Schematic diagram of a triglyceride with a saturated fatty acid (top), a monounsaturated one (middle) and a polyunsaturated one (bottom).
The most common fatty acids in human diet are unsaturated or mono-unsaturated. Monounsaturated fats are found in animal flesh such as red meat, whole milk products, nuts, and high fat fruits such as olives and avocados. Olive oil is about 75% monounsaturated fat.[122] The high oleic variety sunflower oil contains at least 70% monounsaturated fat.[123] Canola oil and cashews are both about 58% monounsaturated fat.[124] Tallow (beef fat) is about 50% monounsaturated fat,[125] and lard is about 40% monounsaturated fat.[126] Other sources include hazelnut, avocado oil, macadamia nut oil, grapeseed oil, groundnut oil (peanut oil), sesame oil, corn oil, popcorn, whole grain wheat, cereal, oatmeal, almond oil, hemp oil, and tea-oil camellia.[127]
Polyunsaturated fatty acids can be found mostly in nuts, seeds, fish, seed oils, and oysters.[128]
Food sources of polyunsaturated fats include:[128][129]
Food source (100g) Polyunsaturated fat (g)
Walnuts 47
Canola oil 34
Sunflower seeds 33
Sesame seeds 26
Chia seeds 23.7
Unsalted peanuts 16
Peanut butter 14.2
Avocado oil 13.5[130]
Olive oil 11
Safflower oil 12.82[131]
Seaweed 11
Sardines 5
Soybeans 7
Tuna 14
Wild salmon 17.3
Whole grain wheat 9.7
Insulin resistance and sensitivity
MUFAs (especially oleic acid) have been found to lower the incidence of insulin resistance; PUFAs (especially large amounts of arachidonic acid) and SFAs (such as arachidic acid) increased it. These ratios can be indexed in the phospholipids of human skeletal muscle and in other tissues as well. This relationship between dietary fats and insulin resistance is presumed secondary to the relationship between insulin resistance and inflammation, which is partially modulated by dietary fat ratios (omega−3/6/9) with both omega−3 and −9 thought to be anti-inflammatory, and omega−6 pro-inflammatory (as well as by numerous other dietary components, particularly polyphenols and exercise, with both of these anti-inflammatory). Although both pro- and anti-inflammatory types of fat are biologically necessary, fat dietary ratios in most US diets are skewed towards omega−6, with subsequent disinhibition of inflammation and potentiation of insulin resistance.[73] This is contrary to the suggestion that polyunsaturated fats are shown to be protective against insulin resistance.[citation needed]
The large scale KANWU study found that increasing MUFA and decreasing SFA intake could improve insulin sensitivity, but only when the overall fat intake of the diet was low.[132] However, some MUFAs may promote insulin resistance (like the SFAs), whereas PUFAs may protect against it.[133][134][clarification needed]
Cancer
Levels of oleic acid along with other MUFAs in red blood cell membranes were positively associated with breast cancer risk. The saturation index (SI) of the same membranes was inversely associated with breast cancer risk. MUFAs and low SI in erythrocyte membranes are predictors of postmenopausal breast cancer. Both of these variables depend on the activity of the enzyme delta-9 desaturase (Δ9-d).[135]
Results from observational clinical trials on PUFA intake and cancer have been inconsistent and vary by numerous factors of cancer incidence, including gender and genetic risk.[136] Some studies have shown associations between higher intakes and/or blood levels of omega-3 PUFAs and a decreased risk of certain cancers, including breast and colorectal cancer, while other studies found no associations with cancer risk.[136][137]
Pregnancy disorders
Polyunsaturated fat supplementation was found to have no effect on the incidence of pregnancy-related disorders, such as hypertension or preeclampsia, but may increase the length of gestation slightly and decreased the incidence of early premature births.[128]
Expert panels in the United States and Europe recommend that pregnant and lactating women consume higher amounts of polyunsaturated fats than the general population to enhance the DHA status of the fetus and newborn.[128]
"Cis fat" vs. "trans fat"
In nature, unsaturated fatty acids generally have double bonds in cis configuration (with the adjacent C–C bonds on the same side) as opposed to trans.[138] Nevertheless, trans fatty acids (TFAs) occur in small amounts in meat and milk of ruminants (such as cattle and sheep),[139][140] typically 2–5% of total fat.[141] Natural TFAs, which include conjugated linoleic acid (CLA) and vaccenic acid, originate in the rumen of these animals. CLA has two double bonds, one in the cis configuration and one in trans, which makes it simultaneously a cis- and a trans-fatty acid.[142]
Trans fat contents in various natural and traditionally processed foods, in g per 100 g [143]
Food type Trans fat content
butter 2 to 7 g
whole milk 0.07 to 0.1 g
animal fat 0 to 5 g[141]
ground beef 1 g
Margarine, a common product that can contain trans fatty acids
Cover of original Crisco cookbook, 1912. Crisco was made by hydrogenating cottonseed oil. The formula was revised in the 2000s and now has only a small amount of trans fat.
Wilhelm Normann patented the hydrogenation of liquid oils in 1902
Concerns about trans fatty acids in human diet were raised when they were found to be an unintentional byproduct of the partial hydrogenation of vegetable and fish oils. While these trans fatty acids (popularly called "trans fats") are edible, they have been implicated in many health problems.[144]
Conversion of cis to trans fatty acids in partial hydrogenation
The hydrogenation process, invented and patented by Wilhelm Normann in 1902, made it possible to turn relatively cheap liquid fats such as whale or fish oil into more solid fats and to extend their shelf-life by preventing rancidification. (The source fat and the process were initially kept secret to avoid consumer distaste.[145]) This process was widely adopted by the food industry in the early 1900s; first for the production of margarine, a replacement for butter and shortening,[146] and eventually for various other fats used in snack food, packaged baked goods, and deep fried products.[147]
Full hydrogenation of a fat or oil produces a fully saturated fat. However, hydrogenation generally was interrupted before completion, to yield a fat product with specific melting point, hardness, and other properties. Partial hydrogenation turns some of the cis double bonds into trans bonds by an isomerization reaction.[147][148] The trans configuration is favored [citation needed] because it is the lower energy form.
This side reaction accounts for most of the trans fatty acids consumed today, by far.[149][150] An analysis of some industrialized foods in 2006 found up to 30% "trans fats" in artificial shortening, 10% in breads and cake products, 8% in cookies and crackers, 4% in salty snacks, 7% in cake frostings and sweets, and 26% in margarine and other processed spreads.[143] Another 2010 analysis however found only 0.2% of trans fats in margarine and other processed spreads.[151] Up to 45% of the total fat in those foods containing man-made trans fats formed by partially hydrogenating plant fats may be trans fat.[141] Baking shortenings, unless reformulated, contain around 30% trans fats compared to their total fats. High-fat dairy products such as butter contain about 4%. Margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight,[152] but some reformulated ones are less than 1% trans fat.
High levels of TFAs have been recorded in popular "fast food" meals.[150] An analysis of samples of McDonald's French fries collected in 2004 and 2005 found that fries served in New York City contained twice as much trans fat as in Hungary, and 28 times as much as in Denmark, where trans fats are restricted. For Kentucky Fried Chicken products, the pattern was reversed: the Hungarian product containing twice the trans fat of the New York product. Even within the United States, there was variation, with fries in New York containing 30% more trans fat than those from Atlanta.[153]
Cardiovascular disease
Numerous studies have found that consumption of TFAs increases risk of cardiovascular disease.[14][5] The Harvard School of Public Health advises that replacing TFAs and saturated fats with cis monounsaturated and polyunsaturated fats is beneficial for health.[154]
Consuming trans fats has been shown to increase the risk of coronary artery disease in part by raising levels of low-density lipoprotein (LDL, often termed "bad cholesterol"), lowering levels of high-density lipoprotein (HDL, often termed "good cholesterol"), increasing triglycerides in the bloodstream and promoting systemic inflammation.[155][156]
The primary health risk identified for trans fat consumption is an elevated risk of coronary artery disease (CAD).[157] A 1994 study estimated that over 30,000 cardiac deaths per year in the United States are attributable to the consumption of trans fats.[158] By 2006 upper estimates of 100,000 deaths were suggested.[159] A comprehensive review of studies of trans fats published in 2006 in the New England Journal of Medicine reports a strong and reliable connection between trans fat consumption and CAD, concluding that "On a per-calorie basis, trans fats appear to increase the risk of CAD more than any other macronutrient, conferring a substantially increased risk at low levels of consumption (1 to 3% of total energy intake)".[160]
The major evidence for the effect of trans fat on CAD comes from the Nurses' Health Study – a cohort study that has been following 120,000 female nurses since its inception in 1976. In this study, Hu and colleagues analyzed data from 900 coronary events from the study's population during 14 years of followup. He determined that a nurse's CAD risk roughly doubled (relative risk of 1.93, CI: 1.43 to 2.61) for each 2% increase in trans fat calories consumed (instead of carbohydrate calories). By contrast, for each 5% increase in saturated fat calories (instead of carbohydrate calories) there was a 17% increase in risk (relative risk of 1.17, CI: 0.97 to 1.41). "The replacement of saturated fat or trans unsaturated fat by cis (unhydrogenated) unsaturated fats was associated with larger reductions in risk than an isocaloric replacement by carbohydrates."[161] Hu also reports on the benefits of reducing trans fat consumption. Replacing 2% of food energy from trans fat with non-trans unsaturated fats more than halves the risk of CAD (53%). By comparison, replacing a larger 5% of food energy from saturated fat with non-trans unsaturated fats reduces the risk of CAD by 43%.[161]
Another study considered deaths due to CAD, with consumption of trans fats being linked to an increase in mortality, and consumption of polyunsaturated fats being linked to a decrease in mortality.[157][162]
Trans fat has been found to act like saturated in raising the blood level of LDL ("bad cholesterol"); but, unlike saturated fat, it also decreases levels of HDL ("good cholesterol"). The net increase in LDL/HDL ratio with trans fat, a widely accepted indicator of risk for coronary artery disease, is approximately double that due to saturated fat.[163][164][165] One randomized crossover study published in 2003 comparing the effect of eating a meal on blood lipids of (relatively) cis and trans-fat-rich meals showed that cholesteryl ester transfer (CET) was 28% higher after the trans meal than after the cis meal and that lipoprotein concentrations were enriched in apolipoprotein(a) after the trans meals.[166]
The citokyne test is a potentially more reliable indicator of CAD risk, although is still being studied.[157] A study of over 700 nurses showed that those in the highest quartile of trans fat consumption had blood levels of C-reactive protein (CRP) that were 73% higher than those in the lowest quartile.[167]
Breast feeding
It has been established that trans fats in human breast milk fluctuate with maternal consumption of trans fat, and that the amount of trans fats in the bloodstream of breastfed infants fluctuates with the amounts found in their milk. In 1999, reported percentages of trans fats (compared to total fats) in human milk ranged from 1% in Spain, 2% in France, 4% in Germany, and 7% in Canada and the United States.[168]
Other health risks
There are suggestions that the negative consequences of trans fat consumption go beyond the cardiovascular risk. In general, there is much less scientific consensus asserting that eating trans fat specifically increases the risk of other chronic health problems:
Alzheimer's disease: A study published in Archives of Neurology in February 2003 suggested that the intake of both trans fats and saturated fats promotes the development of Alzheimer disease,[169] although not confirmed in an animal model.[170] It has been found that trans fats impaired memory and learning in middle-age rats. The brains of rats that ate trans-fats had fewer proteins critical to healthy neurological function. Inflammation in and around the hippocampus, the part of the brain responsible for learning and memory. These are the exact types of changes normally seen at the onset of Alzheimer's, but seen after six weeks, even though the rats were still young.[171]
Cancer: There is no scientific consensus that consuming trans fats significantly increases cancer risks across the board.[157] The American Cancer Society states that a relationship between trans fats and cancer "has not been determined."[172] One study has found a positive connection between trans fat and prostate cancer.[173] However, a larger study found a correlation between trans fats and a significant decrease in high-grade prostate cancer.[174] An increased intake of trans fatty acids may raise the risk of breast cancer by 75%, suggest the results from the French part of the European Prospective Investigation into Cancer and Nutrition.[175][176]
Diabetes: There is a growing concern that the risk of type 2 diabetes increases with trans fat consumption.[157][177] However, consensus has not been reached.[160] For example, one study found that risk is higher for those in the highest quartile of trans fat consumption.[178] Another study has found no diabetes risk once other factors such as total fat intake and BMI were accounted for.[179]
Obesity: Research indicates that trans fat may increase weight gain and abdominal fat, despite a similar caloric intake.[180] A 6-year experiment revealed that monkeys fed a trans fat diet gained 7.2% of their body weight, as compared to 1.8% for monkeys on a mono-unsaturated fat diet.[181][182] Although obesity is frequently linked to trans fat in the popular media,[183] this is generally in the context of eating too many calories; there is not a strong scientific consensus connecting trans fat and obesity, although the 6-year experiment did find such a link, concluding that "under controlled feeding conditions, long-term TFA consumption was an independent factor in weight gain. TFAs enhanced intra-abdominal deposition of fat, even in the absence of caloric excess, and were associated with insulin resistance, with evidence that there is impaired post-insulin receptor binding signal transduction."[182]
Infertility in women: One 2007 study found, "Each 2% increase in the intake of execution of a specific body function form an organ system, also called a biological system or body system.
An organ's tissues can be broadly categorized as parenchyma, the functional tissue, and stroma, the structural tissue with supportive, connective, or ancillary functions. For example, the gland's tissue that makes the hormones is the parenchyma, whereas the stroma includes the nerves that innervate the parenchyma, the blood vessels that oxygenate and nourish it and carry away its metabolic wastes, and the connective tissues that provide a suitable place for it to be situated and anchored. The main tissues that make up an organ tend to have common embryologic origins, such as arising from the same germ layer. Organs exist in most multicellular organisms. In single-celled organisms such as members of the eukaryotes, the functional analogue of an organ is known as an organelle. In plants, there are three main organs.[3]
The number of organs in any organism depends on the definition used. By one widely adopted definition, 79 organs have been identified in the human body.[4]
Animals
See also: List of organs of the human body and Biological system
The liver and gallbladder of a sheep
Except for placozoans, multicellular animals including humans have a variety of organ systems. These specific systems are widely studied in human anatomy. The functions of these organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamus. For this reason, the two systems are combined and studied as the neuroendocrine system. The same is true for the musculoskeletal system because of the relationship between the muscular and skeletal systems.
Cardiovascular system: pumping and channeling blood to and from the body and lungs with heart, blood and blood vessels.
Digestive system: digestion and processing food with salivary glands, esophagus, stomach, liver, gallbladder, pancreas, intestines, colon, mesentery, rectum and anus.
Endocrine system: communication within the body using hormones made by endocrine glands such as the hypothalamus, pituitary gland, pineal body or pineal gland, thyroid, parathyroids and adrenals, i.e., adrenal glands.
Excretory system: kidneys, ureters, bladder and urethra involved in fluid balance, electrolyte balance and excretion of urine.
Lymphatic system: structures involved in the transfer of lymph between tissues and the blood stream, the lymph and the nodes and vessels that transport it including the immune system: defending against disease-causing agents with leukocytes, tonsils, adenoids, thymus and spleen.
Integumentary system: skin, hair and nails of mammals. Also scales of fish, reptiles, and birds, and feathers of birds.
Muscular system: movement with muscles.
Nervous system: collecting, transferring and processing information with brain, spinal cord and nerves.
Reproductive system: the sex organs, such as ovaries, oviducts, uterus, vulva, vagina, testicles, vas deferens, seminal vesicles, prostate and penis.
Respiratory system: the organs used for breathing, the pharynx, larynx, trachea, bronchi, lungs and diaphragm.
Skeletal system: structural support and protection with bones, cartilage, ligaments and tendons.
Viscera
In the study of anatomy, viscera (sg.: viscus) refers to the internal organs of the abdominal, thoracic, and pelvic cavities.[5] The abdominal organs may be classified as solid organs or hollow organs. The solid organs are the liver, pancreas, spleen, kidneys, and adrenal glands. The hollow organs of the abdomen are the stomach, intestines, gallbladder, bladder, and rectum.[6] In the thoracic cavity, the heart is a hollow, muscular organ.[7] Splanchnology is the study of the viscera.[8] The term "visceral" is contrasted with the term "parietal", meaning "of or relating to the wall of a body part, organ or cavity".[9] The two terms are often used in describing a membrane or piece of connective tissue, referring to the opposing sides.[10]
Origin and evolution
Relationship of major animal lineages with indication of how long ago these animals shared a common ancestor. On the left, important organs are shown, which allows us to determine how long ago these may have evolved.
The organ level of organisation in animals can be first detected in flatworms and the more derived phyla, i.e. the bilaterians. The less-advanced taxa (i.e. Placozoa, Porifera, Ctenophora and Cnidaria) do not show consolidation of their tissues into organs.
More complex animals are composed of different organs, which have evolved over time. For example, the liver and heart evolved in the chordates about 550-500 million years ago, while the gut and brain are even more ancient, arising in the ancestor of vertebrates, insects, molluscs, and worms about 700-650 million years ago.
Given the ancient origin of most vertebrate organs, researchers have looked for model systems, where organs have evolved more recently, and ideally have evolved multiple times independently. An outstanding model for this kind of research is the placenta, which has evolved more than 100 times independently in vertebrates, has evolved relatively recently in some lineages, and exists in intermediate forms in extant taxa.[11] Studies on the evolution of the placenta have identified a variety of genetic and physiological processes that contribute to the origin and evolution of organs, these include the re-purposing of existing animal tissues, the acquisition of new functional properties by these tissues, and novel interactions of distinct tissue types.[11]
Plants
See also: Plant morphology, Plant anatomy, and Plant physiology
The flower is the angiosperm's reproductive organ. This Hibiscus flower is hermaphroditic, and it contains stamen and pistils.
Strobilus of Equisetum telmateia
The study of plant organs is covered in plant morphology. Organs of plants can be divided into vegetative and reproductive. Vegetative plant organs include roots, stems, and leaves. The reproductive organs are variable. In flowering plants, they are represented by the flower, seed and fruit.[citation needed] In conifers, the organ that bears the reproductive structures is called a cone. In other divisions (phyla) of plants, the reproductive organs are called strobili, in Lycopodiophyta, or simply gametophores in mosses. Common organ system designations in plants include the differentiation of shoot and root. All parts of the plant above ground (in non-epiphytes), including the functionally distinct leaf and flower organs, may be classified together as the shoot organ system.[12]
The vegetative organs are essential for maintaining the life of a plant. While there can be 11 organ systems in animals, there are far fewer in plants, where some perform the vital functions, such as photosynthesis, while the reproductive organs are essential in reproduction. However, if there is asexual vegetative reproduction, the vegetative organs are those that create the new generation of plants (see clonal colony).
Society and culture
Many societies have a system for organ donation, in which a living or deceased donor's organ are transplanted into a person with a failing organ. The transplantation of larger solid organs often requires immunosuppression to prevent organ rejection or graft-versus-host disease.
There is considerable interest throughout the world in creating laboratory-grown or artificial organs.[citation needed]
Organ transplants
Beginning in the 20th century[13] organ transplants began to take place as scientists knew more about the anatomy of organs. These came later in time as procedures were often dangerous and difficult.[14] Both the source and method of obtaining the organ to transplant are major ethical issues to consider, and because organs as resources for transplant are always more limited than demand for them, various notions of justice, including distributive justice, are developed in the ethical analysis. This situation continues as long as transplantation relies upon organ donors rather than technological innovation, testing, and industrial manufacturing.[citation needed]
History
Human viscera
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This section needs expansion. You can help by adding to it. (February 2018)
The English word "organ" dates back to the twelfth century and refers to any musical instrument. By the late 14th century, the musical term's meaning had narrowed to refer specifically to the keyboard-based instrument. At the same time, a second meaning arose, in reference to a "body part adapted to a certain function".[15]
Plant organs are made from tissue composed of different types of tissue. The three tissue types are ground, vascular, and dermal.[16] When three or more organs are present, it is called an organ system.[17]
The adjective visceral, also splanchnic, is used for anything pertaining to the internal organs. Historically, viscera of animals were examined by Roman pagan priests like the haruspices or the augurs in order to divine the future by their shape, dimensions or other factors.[18] This practice remains an important ritual in some remote, tribal societies.
The term "visceral" is contrasted with the term "parietal", meaning "of or relating to the wall of a body part, organ or cavity"[9] The two terms are often used in describing a membrane or piece of connective tissue, referring to the opposing sides.[19]
Antiquity
Aristotle used the word frequently in his philosophy, both to describe the organs of plants or animals (e.g. the roots of a tree, the heart or liver of an animal), and to describe more abstract "parts" of an interconnected whole (e.g. his logical works, taken as a whole, are referred to as the Organon).[20]
Some alchemists (e.g. Paracelsus) adopted the Hermetic Qabalah assignment between the seven vital organs and the seven classical planets as follows: [21]
Planet Organ
Sun Heart
Moon Brain
Mercury Lungs
Venus Kidneys
Mars Gall bladder
Jupiter Liver
Saturn Spleen
The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before being removed by defecation.[1] The colon is the longest portion of the large intestine, and the terms are often used interchangeably but most sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal.[1][2][3] Some other sources exclude the anal canal.[4][5][6]
In humans, the large intestine begins in the right iliac region of the pelvis, just at or below the waist, where it is joined to the end of the small intestine at the cecum, via the ileocecal valve. It then continues as the colon ascending the abdomen, across the width of the abdominal cavity as the transverse colon, and then descending to the rectum and its endpoint at the anal canal.[7] Overall, in humans, the large intestine is about 1.5 metres (5 ft) long, which is about one-fifth of the whole length of the human gastrointestinal tract.[8]
Structure
Illustration of the large intestine.
The colon of the large intestine is the last part of the digestive system. It has a segmented appearance due to a series of saccules called haustra.[9] It extracts water and salt from solid wastes before they are eliminated from the body and is the site in which the fermentation of unabsorbed material by the gut microbiota occurs. Unlike the small intestine, the colon does not play a major role in absorption of foods and nutrients. About 1.5 litres or 45 ounces of water arrives in the colon each day.[10]
The colon is the longest part of the large intestine and its average length in the adult human is 65 inches or 166 cm (range of 80 to 313 cm) for males, and 61 inches or 155 cm (range of 80 to 214 cm) for females.[11]
Sections
Inner diameters of colon sections
In mammals, the large intestine consists of the cecum (including the appendix), colon (the longest part), rectum, and anal canal.[1]
The four sections of the colon are: the ascending colon, transverse colon, descending colon, and sigmoid colon. These sections turn at the colic flexures.
The parts of the colon are either intraperitoneal or behind it in the retroperitoneum. Retroperitoneal organs, in general, do not have a complete covering of peritoneum, so they are fixed in location. Intraperitoneal organs are completely surrounded by peritoneum and are therefore mobile.[12] Of the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the cecum, appendix, transverse colon and sigmoid colon are intraperitoneal.[13] This is important as it affects which organs can be easily accessed during surgery, such as a laparotomy.
In terms of diameter, the cecum is the widest, averaging slightly less than 9 cm in healthy individuals, and the transverse colon averages less than 6 cm in diameter.[14] The descending and sigmoid colon are slightly smaller, with the sigmoid colon averaging 4–5 cm (1.6–2.0 in) in diameter.[14][15] Diameters larger than certain thresholds for each colonic section can be diagnostic for megacolon.
3D file generated from computed tomography of large intestine
Cecum and appendix
Main articles: Cecum and Appendix (anatomy)
The cecum is the first section of the large intestine and is involved in digestion, while the appendix which develops embryologically from it, is not involved in digestion and is considered to be part of the gut-associated lymphoid tissue. The function of the appendix is uncertain, but some sources believe that it has a role in housing a sample of the gut microbiota, and is able to help to repopulate the colon with microbiota if depleted during the course of an immune reaction. The appendix has also been shown to have a high concentration of lymphatic cells.
Ascending colon
Main article: Ascending colon
The ascending colon is the first of four main sections of the large intestine. It is connected to the small intestine by a section of bowel called the cecum. The ascending colon runs upwards through the abdominal cavity toward the transverse colon for approximately eight inches (20 cm).
One of the main functions of the colon is to remove the water and other key nutrients from waste material and recycle it. As the waste material exits the small intestine through the ileocecal valve, it will move into the cecum and then to the ascending colon where this process of extraction starts. The waste material is pumped upwards toward the transverse colon by peristalsis. The ascending colon is sometimes attached to the appendix via Gerlach's valve. In ruminants, the ascending colon is known as the spiral colon.[16][17][18] Taking into account all ages and sexes, colon cancer occurs here most often (41%).[19]
Transverse colon
Main article: Transverse colon
The transverse colon is the part of the colon from the hepatic flexure, also known as the right colic, (the turn of the colon by the liver) to the splenic flexure also known as the left colic, (the turn of the colon by the spleen). The transverse colon hangs off the stomach, attached to it by a large fold of peritoneum called the greater omentum. On the posterior side, the transverse colon is connected to the posterior abdominal wall by a mesentery known as the transverse mesocolon.
The transverse colon is encased in peritoneum, and is therefore mobile (unlike the parts of the colon immediately before and after it).
The proximal two-thirds of the transverse colon is perfused by the middle colic artery, a branch of the superior mesenteric artery (SMA), while the latter third is supplied by branches of the inferior mesenteric artery (IMA). The "watershed" area between these two blood supplies, which represents the embryologic division between the midgut and hindgut, is an area sensitive to ischemia.
Descending colon
Main article: Descending colon
The descending colon is the part of the colon from the splenic flexure to the beginning of the sigmoid colon. One function of the descending colon in the digestive system is to store feces that will be emptied into the rectum. It is retroperitoneal in two-thirds of humans. In the other third, it has a (usually short) mesentery.[20] The arterial supply comes via the left colic artery. The descending colon is also called the distal gut, as it is further along the gastrointestinal tract than the proximal gut. Gut flora are very dense in this region.
Sigmoid colon
Main article: Sigmoid colon
The sigmoid colon is the part of the large intestine after the descending colon and before the rectum. The name sigmoid means S-shaped (see sigmoid; cf. sigmoid sinus). The walls of the sigmoid colon are muscular and contract to increase the pressure inside the colon, causing the stool to move into the rectum.
The sigmoid colon is supplied with blood from several branches (usually between 2 and 6) of the sigmoid arteries, a branch of the IMA. The IMA terminates as the superior rectal artery.
Sigmoidoscopy is a common diagnostic technique used to examine the sigmoid colon.
Rectum
Main article: Rectum
The rectum is the last section of the large intestine. It holds the formed feces awaiting elimination via defecation. It is about 12 cm long.[21]
Appearance
The cecum – the first part of the large intestine
Taeniae coli – three bands of smooth muscle
Haustra – bulges caused by contraction of taeniae coli
Epiploic appendages – small fat accumulations on the viscera
The taenia coli run the length of the large intestine. Because the taenia coli are shorter than the large bowel itself, the colon becomes sacculated, forming the haustra of the colon which are the shelf-like intraluminal projections.[22]
Blood supply
Arterial supply to the colon comes from branches of the superior mesenteric artery (SMA) and inferior mesenteric artery (IMA). Flow between these two systems communicates via the marginal artery of the colon that runs parallel to the colon for its entire length. Historically, a structure variously identified as the arc of Riolan or meandering mesenteric artery (of Moskowitz) was thought to connect the proximal SMA to the proximal IMA. This variably present structure would be important if either vessel were occluded. However, at least one review of the literature questions the existence of this vessel, with some experts calling for the abolition of these terms from future medical literature.[23]
Venous drainage usually mirrors colonic arterial supply, with the inferior mesenteric vein draining into the splenic vein, and the superior mesenteric vein joining the splenic vein to form the hepatic portal vein that then enters the liver. Middle rectal veins are an exception, delivering blood to inferior vena cava and bypassing the liver.[24]
Lymphatic drainage
Lymphatic drainage from the ascending colon and proximal two-thirds of the transverse colon is to the ileocolic lymph nodes and the superior mesenteric lymph nodes, which drain into the cisterna chyli.[25] The lymph from the distal one-third of the transverse colon, the descending colon, the sigmoid colon, and the upper rectum drain into the inferior mesenteric and colic lymph nodes.[25] The lower rectum to the anal canal above the pectinate line drain to the internal ileocolic nodes.[26] The anal canal below the pectinate line drains into the superficial inguinal nodes.[26] The pectinate line only roughly marks this transition.
Nerve supply
Sympathetic supply: superior & inferior mesenteric ganglia; parasympathetic supply: vagus & pelvic nerves
Development
See also: Development of the digestive system
The endoderm, mesoderm and ectoderm are germ layers that develop in a process called gastrulation. Gastrulation occurs early in human development. The gastrointestinal tract is derived from these layers.[27]
Variation
One variation on the normal anatomy of the colon occurs when extra loops form, resulting in a colon that is up to five metres longer than normal. This condition, referred to as redundant colon, typically has no direct major health consequences, though rarely volvulus occurs, resulting in obstruction and requiring immediate medical attention.[28][29] A significant indirect health consequence is that use of a standard adult colonoscope is difficult and in some cases impossible when a redundant colon is present, though specialized variants on the instrument (including the pediatric variant) are useful in overcoming this problem.[30]
Microanatomy
Further information: Gastrointestinal wall
Colonic crypts
Colonic crypts (intestinal glands) within four tissue sections. The cells have been stained to show a brown-orange color if the cells produce the mitochondrial protein cytochrome c oxidase subunit I (CCOI), and the nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin. Panels A, B were cut across the long axes of the crypts and panels C, D were cut parallel to the long axes of the crypts. In panel A the bar shows 100 μm and allows an estimate of the frequency of crypts in the colonic epithelium. Panel B includes three crypts in cross-section, each with one segment deficient for CCOI expression and at least one crypt, on the right side, undergoing fission into two crypts. Panel C shows, on the left side, a crypt fissioning into two crypts. Panel D shows typical small clusters of two and three CCOI deficient crypts (the bar shows 50 μm). The images were made from original photomicrographs, but panels A, B and D were also included in an article[31] and illustrations were published with Creative Commons Attribution-Noncommercial License allowing re-use.
The wall of the large intestine is lined with simple columnar epithelium with invaginations. The invaginations are called the intestinal glands or colonic crypts.
Micrograph of normal large instestinal crypts.
Micrograph of normal large instestinal crypts.
Anatomy of normal large intestinal crypts
Anatomy of normal large intestinal crypts
The colon crypts are shaped like microscopic thick walled test tubes with a central hole down the length of the tube (the crypt lumen). Four tissue sections are shown here, two cut across the long axes of the crypts and two cut parallel to the long axes. In these images the cells have been stained by immunohistochemistry to show a brown-orange color if the cells produce a mitochondrial protein called cytochrome c oxidase subunit I (CCOI). The nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin. As seen in panels C and D, crypts are about 75 to about 110 cells long. Baker et al.[32] found that the average crypt circumference is 23 cells. Thus, by the images shown here, there are an average of about 1,725 to 2,530 cells per colonic crypt. Nooteboom et al.[33] measuring the number of cells in a small number of crypts reported a range of 1,500 to 4,900 cells per colonic crypt. Cells are produced at the crypt base and migrate upward along the crypt axis before being shed into the colonic lumen days later.[32] There are 5 to 6 stem cells at the bases of the crypts.[32]
As estimated from the image in panel A, there are about 100 colonic crypts per square millimeter of the colonic epithelium.[34] Since the average length of the human colon is 160.5 cm[11] and the average inner circumference of the colon is 6.2 cm,[34] the inner surface epithelial area of the human colon has an average area of about 995 cm2, which includes 9,950,000 (close to 10 million) crypts.
In the four tissue sections shown here, many of the intestinal glands have cells with a mitochondrial DNA mutation in the CCOI gene and appear mostly white, with their main color being the blue-gray staining of the nuclei. As seen in panel B, a portion of the stem cells of three crypts appear to have a mutation in CCOI, so that 40% to 50% of the cells arising from those stem cells form a white segment in the cross cut area.
Overall, the percent of crypts deficient for CCOI is less than 1% before age 40, but then increases linearly with age.[31] Colonic crypts deficient for CCOI in women reaches, on average, 18% in women and 23% in men by 80–84 years of age.[31]
Crypts of the colon can reproduce by fission, as seen in panel C, where a crypt is fissioning to form two crypts, and in panel B where at least one crypt appears to be fissioning. Most crypts deficient in CCOI are in clusters of crypts (clones of crypts) with two or more CCOI-deficient crypts adjacent to each other (see panel D).[31]
Mucosa
About 150 of the many thousands of protein coding genes expressed in the large intestine, some are specific to the mucous membrane in different regions and include CEACAM7.[35]
Function
Histological section.
The large intestine absorbs water and any remaining absorbable nutrients from the food before sending the indigestible matter to the rectum. The colon absorbs vitamins that are created by the colonic bacteria, such as thiamine, riboflavin, and vitamin K (especially important as the daily ingestion of vitamin K is not normally enough to maintain adequate blood coagulation).[36][citation needed][37] It also compacts feces, and stores fecal matter in the rectum until it can be discharged via the anus in defecation.
The large intestine also secretes K+ and Cl-. Chloride secretion increases in cystic fibrosis. Recycling of various nutrients takes place in the colon. Examples include fermentation of carbohydrates, short chain fatty acids, and urea cycling.[38][citation needed]
The appendix contains a small amount of mucosa-associated lymphoid tissue which gives the appendix an undetermined role in immunity. However, the appendix is known to be important in fetal life as it contains endocrine cells that release biogenic amines and peptide hormones important for homeostasis during early growth and development.[39]
By the time the chyme has reached this tube, most nutrients and 90% of the water have been absorbed by the body. Indeed, as demonstrated by the commonality of ileostomy procedures, it is possible for many people to live without large portions of their large intestine, or even without it completely. At this point only some electrolytes like sodium, magnesium, and chloride are left as well as indigestible parts of ingested food (e.g., a large part of ingested amylose, starch which has been shielded from digestion heretofore, and dietary fiber, which is largely indigestible carbohydrate in either soluble or insoluble form). As the chyme moves through the large intestine, most of the remaining water is removed, while the chyme is mixed with mucus and bacteria (known as gut flora), and becomes feces. The ascending colon receives fecal material as a liquid. The muscles of the colon then move the watery waste material forward and slowly absorb all the excess water, causing the stools to gradually solidify as they move along into the descending colon.[40]
The bacteria break down some of the fiber for their own nourishment and create acetate, propionate, and butyrate as waste products, which in turn are used by the cell lining of the colon for nourishment.[41] No protein is made available. In humans, perhaps 10% of the undigested carbohydrate thus becomes available, though this may vary with diet;[42] in other animals, including other apes and primates, who have proportionally larger colons, more is made available, thus permitting a higher portion of plant material in the diet. The large intestine[43] produces no digestive enzymes — chemical digestion is completed in the small intestine before the chyme reaches the large intestine. The pH in the colon varies between 5.5 and 7 (slightly acidic to neutral).[44]
Standing gradient osmosis
Water absorption at the colon typically proceeds against a transmucosal osmotic pressure gradient. The standing gradient osmosis is the reabsorption of water against the osmotic gradient in the intestines. Cells occupying the intestinal lining pump sodium ions into the intercellular space, raising the osmolarity of the intercellular fluid. This hypertonic fluid creates an osmotic pressure that drives water into the lateral intercellular spaces by osmosis via tight junctions and adjacent cells, which then in turn moves across the basement membrane and into the capillaries, while more sodium ions are pumped again into the intercellular fluid.[45] Although water travels down an osmotic gradient in each individual step, overall, water usually travels against the osmotic gradient due to the pumping of sodium ions into the intercellular fluid. This allows the large intestine to absorb water despite the blood in capillaries being hypotonic compared to the fluid within the intestinal lumen.
Gut flora
Main article: Gut microbiota
The large intestine houses over 700 species of bacteria that perform a variety of functions, as well as fungi, protozoa, and archaea. Species diversity varies by geography and diet.[46] The microbes in a human distal gut often number in the vicinity of 100 trillion, and can weigh around 200 grams (0.44 pounds). This mass of mostly symbiotic microbes has recently been called the latest human organ to be "discovered" or in other words, the "forgotten organ".[47]
The large intestine absorbs some of the products formed by the bacteria inhabiting this region. Undigested polysaccharides (fiber) are metabolized to short-chain fatty acids by bacteria in the large intestine and absorbed by passive diffusion. The bicarbonate that the large intestine secretes helps to neutralize the increased acidity resulting from the formation of these fatty acids.[48]
These bacteria also produce large amounts of vitamins, especially vitamin K and biotin (a B vitamin), for absorption into the blood. Although this source of vitamins, in general, provides only a small part of the daily requirement, it makes a significant contribution when dietary vitamin intake is low. An individual who depends on absorption of vitamins formed by bacteria in the large intestine may become vitamin-deficient if treated with antibiotics that inhibit the vitamin producing species of bacteria as well as the intended disease-causing bacteria.[49]
Other bacterial products include gas (flatus), which is a mixture of nitrogen and carbon dioxide, with small amounts of the gases hydrogen, methane, and hydrogen sulfide. Bacterial fermentation of undigested polysaccharides produces these. Some of the fecal odor is due to indoles, metabolized from the amino acid tryptophan. The normal flora is also essential in the development of certain tissues, including the cecum and lymphatics.[citation needed]
They are also involved in the production of cross-reactive antibodies. These are antibodies produced by the immune system against the normal flora, that are also effective against related pathogens, thereby preventing infection or invasion.
The two most prevalent phyla of the colon are Bacillota and Bacteroidota. The ratio between the two seems to vary widely as reported by the Human Microbiome Project.[50] Bacteroides are implicated in the initiation of colitis and colon cancer. Bifidobacteria are also abundant, and are often described as 'friendly bacteria'.[51][52]
A mucus layer protects the large intestine from attacks from colonic commensal bacteria.[53]
Clinical significance
Disease
Main article: Gastrointestinal disease
Following are the most common diseases or disorders of the colon:
Angiodysplasia of the colon
Appendicitis
Chronic functional abdominal pain
Colitis
Colorectal cancer
Colorectal polyp
Constipation
Crohn's disease
Diarrhea
Diverticulitis
Diverticulosis
Hirschsprung's disease (aganglionosis)
Ileus
Intussusception
Irritable bowel syndrome
Pseudomembranous colitis
Ulcerative colitis and toxic megacolon
Colonoscopy
Main article: Colonoscopy
Colonoscopy image, splenic flexure,
normal mucosa. The spleen can be seen through it
Colonoscopy is the endoscopic examination of the large intestine and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions. Colonoscopy can remove polyps as small as one millimetre or less. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. It takes 15 years or fewer for a polyp to turn cancerous.
Colonoscopy is similar to sigmoidoscopy—the difference being related to which parts of the colon each can examine. A colonoscopy allows an examination of the entire colon (1200–1500 mm in length). A sigmoidoscopy allows an examination of the distal portion (about 600 mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon.[54][55][56]
A sigmoidoscopy is often used as a screening procedure for a full colonoscopy, often done in conjunction with a stool-based test such as a fecal occult blood test (FOBT), fecal immunochemical test (FIT), or multi-target stool DNA test (Cologuard) or blood-based test, SEPT9 DNA methylation test (Epi proColon).[57] About 5% of these screened patients are referred to colonoscopy.[58]
Virtual colonoscopy, which uses 2D and 3D imagery reconstructed from computed tomography (CT) scans or from nuclear magnetic resonance (MR) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation regarding its diagnostic abilities. Furthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumour removal or biopsy nor visualization of lesions smaller than 5 millimeters. If a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed. Additionally, surgeons have lately been using the term pouchoscopy to refer to a colonoscopy of the ileo-anal pouch.
Other animals
The large intestine is truly distinct only in tetrapods, in which it is almost always separated from the small intestine by an ileocaecal valve. In most vertebrates, however, it is a relatively short structure running directly to the anus, although noticeably wider than the small intestine. Although the caecum is present in most amniotes, only in mammals does the remainder of the large intestine develop into a true colon.[59]
In some small mammals, the colon is straight, as it is in other tetrapods, but, in the majority of mammalian species, it is divided into ascending and descending portions; a distinct transverse colon is typically present only in primates. However, the taeniae coli and accompanying haustra are not found in either carnivorans or ruminants. The rectum of mammals (other than monotremes) is derived from the cloaca of other vertebrates, and is, therefore, not truly homologous with the "rectum" found in these species.[59]
In some fish, there is no true large intestine, but simply a short rectum connecting the end of the digestive part of the gut to the cloaca. In sharks, this includes a rectal gland that secretes salt to help the animal maintain osmotic balance with the seawater. The gland somewhat resembles a caecum in structure but is not a homologous structure\
Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day.[2] It often lasts for a few days and can result in dehydration due to fluid loss.[2] Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour.[2] This can progress to decreased urination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe.[2] Loose but non-watery stools in babies who are exclusively breastfed, however, are normal.[2]
What is diarrhea, how is it caused, treated and prevented (see also script).
Bristol stool scale
The most common cause is an infection of the intestines due to a virus, bacterium, or parasite—a condition also known as gastroenteritis.[2] These infections are often acquired from food or water that has been contaminated by feces, or directly from another person who is infected.[2] The three types of diarrhea are: short duration watery diarrhea, short duration bloody diarrhea, and persistent diarrhea (lasting more than two weeks, which can be either watery or bloody).[2] The short duration watery diarrhea may be due to cholera, although this is rare in the developed world.[2] If blood is present, it is also known as dysentery.[2] A number of non-infectious causes can result in diarrhea.[5] These include lactose intolerance, irritable bowel syndrome, non-celiac gluten sensitivity, celiac disease, inflammatory bowel disease such as ulcerative colitis, hyperthyroidism, bile acid diarrhea, and a number of medications.[5][6][7] In most cases, stool cultures to confirm the exact cause are not required.[8]
Diarrhea can be prevented by improved sanitation, clean drinking water, and hand washing with soap.[2] Breastfeeding for at least six months and vaccination against rotavirus is also recommended.[2] Oral rehydration solution (ORS)—clean water with modest amounts of salts and sugar—is the treatment of choice.[2] Zinc tablets are also recommended.[2] These treatments have been estimated to have saved 50 million children in the past 25 years.[1] When people have diarrhea it is recommended that they continue to eat healthy food, and babies continue to be breastfed.[2] If commercial ORS is not available, homemade solutions may be used.[9] In those with severe dehydration, intravenous fluids may be required.[2] Most cases, however, can be managed well with fluids by mouth.[10] Antibiotics, while rarely used, may be recommended in a few cases such as those who have bloody diarrhea and a high fever, those with severe diarrhea following travelling, and those who grow specific bacteria or parasites in their stool.[8] Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease.[8]
About 1.7 to 5 billion cases of diarrhea occur per year.[2][5][11] It is most common in developing countries, where young children get diarrhea on average three times a year.[2] Total deaths from diarrhea are estimated at 1.53 million in 2019—down from 2.9 million in 1990.[4] In 2012, it was the second most common cause of deaths in children younger than five (0.76 million or 11%).[2][12] Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age.[2] Other long term problems that can result include stunted growth and poor intellectual development.[12]
Terminology
The word diarrhea is from the Ancient Greek διάρροια from διά dia "through" and ῥέω rheo "flow".
Diarrhea is the spelling in American English, whereas diarrhoea is the spelling in British English.
Slang terms for the condition include "the runs", "the squirts" (or "squits" in Britain[13]) and "the trots".[14][15]
The word is often pronounced as /ˌdaɪəˈriːə/ DY-ə-REE-ə.
Definition
Diarrhea is defined by the World Health Organization as having three or more loose or liquid stools per day, or as having more stools than is normal for that person.[2]
Acute diarrhea is defined as an abnormally frequent discharge of semisolid or fluid fecal matter from the bowel, lasting less than 14 days, by World Gastroenterology Organization.[16] Acute diarrhea that is watery may be known as AWD (Acute Watery Diarrhoea.)[17]
Secretory
Secretory diarrhea means that there is an increase in the active secretion, or there is an inhibition of absorption. There is little to no structural damage. The most common cause of this type of diarrhea is a cholera toxin that stimulates the secretion of anions, especially chloride ions (Cl–). Therefore, to maintain a charge balance in the gastrointestinal tract, sodium (Na+) is carried with it, along with water. In this type of diarrhea intestinal fluid secretion is isotonic with plasma even during fasting.[18][19] It continues even when there is no oral food intake.
Osmotic
Osmotic diarrhea occurs when too much water is drawn into the bowels. If a person drinks solutions with excessive sugar or excessive salt, these can draw water from the body into the bowel and cause osmotic diarrhea.[20][19] Osmotic diarrhea can also result from maldigestion, e.g. pancreatic disease or coeliac disease, in which the nutrients are left in the lumen to pull in water. Or it can be caused by osmotic laxatives (which work to alleviate constipation by drawing water into the bowels). In healthy individuals, too much magnesium or vitamin C or undigested lactose can produce osmotic diarrhea and distention of the bowel. A person who has lactose intolerance can have difficulty absorbing lactose after an extraordinarily high intake of dairy products. In persons who have fructose malabsorption, excess fructose intake can also cause diarrhea. High-fructose foods that also have a high glucose content are more absorbable and less likely to cause diarrhea. Sugar alcohols such as sorbitol (often found in sugar-free foods) are difficult for the body to absorb and, in large amounts, may lead to osmotic diarrhea.[18] In most of these cases, osmotic diarrhea stops when the offending agent, e.g. milk or sorbitol, is stopped.
Exudative
Exudative diarrhea occurs with the presence of blood and pus in the stool. This occurs with inflammatory bowel diseases, such as Crohn's disease or ulcerative colitis, and other severe infections such as E. coli or other forms of food poisoning.[19][18]
Inflammatory
Inflammatory diarrhea occurs when there is damage to the mucosal lining or brush border, which leads to a passive loss of protein-rich fluids and a decreased ability to absorb these lost fluids. Features of all three of the other types of diarrhea can be found in this type of diarrhea.[21] It can be caused by bacterial infections, viral infections, parasitic infections, or autoimmune problems such as inflammatory bowel diseases. It can also be caused by tuberculosis, colon cancer, and enteritis.[19]
Dysentery
If there is blood visible in the stools, it is also known as dysentery. The blood is a trace of an invasion of bowel tissue. Dysentery is a symptom of, among others, Shigella, Entamoeba histolytica, and Salmonella.[19]
Health effects
Diarrheal disease may have a negative impact on both physical fitness and mental development. "Early childhood malnutrition resulting from any cause reduces physical fitness and work productivity in adults,"[22] and diarrhea is a primary cause of childhood malnutrition.[23] Further, evidence suggests that diarrheal disease has significant impacts on mental development and health; it has been shown that, even when controlling for helminth infection and early breastfeeding, children who had experienced severe diarrhea had significantly lower scores on a series of tests of intelligence.[22][24]
Diarrhea can cause electrolyte imbalances, kidney impairment, dehydration, and defective immune system responses. When oral drugs are administered, the efficiency of the drug is to produce a therapeutic effect and the lack of this effect may be due to the medication travelling too quickly through the digestive system, limiting the time that it can be absorbed. Clinicians try to treat the diarrheas by reducing the dosage of medication, changing the dosing schedule, discontinuation of the drug, and rehydration. The interventions to control the diarrhea are not often effective. Diarrhea can have a profound effect on the quality of life because fecal incontinence is one of the leading factors for placing older adults in long term care facilities (nursing homes).[19]
Causes
Diagram of the human gastrointestinal tract
In the latter stages of human digestion, ingested materials are inundated with water and digestive fluids such as gastric acid, bile, and digestive enzymes in order to break them down into their nutrient components, which are then absorbed into the bloodstream via the intestinal tract in the small intestine. Prior to defecation, the large intestine reabsorbs the water and other digestive solvents in the waste product in order to maintain proper hydration and overall equilibrium.[25] Diarrhea occurs when the large intestine is prevented, for any number of reasons, from sufficiently absorbing the water or other digestive fluids from fecal matter, resulting in a liquid, or "loose", bowel movement.[26]
Acute diarrhea is most commonly due to viral gastroenteritis with rotavirus, which accounts for 40% of cases in children under five.[1] In travelers, however, bacterial infections predominate.[27] Various toxins such as mushroom poisoning and drugs can also cause acute diarrhea.
Chronic diarrhea can be the part of the presentations of a number of chronic medical conditions affecting the intestine. Common causes include ulcerative colitis, Crohn's disease, microscopic colitis, celiac disease, irritable bowel syndrome, and bile acid malabsorption.[28]
Infections
Main article: Infectious diarrhea
There are many causes of infectious diarrhea, which include viruses, bacteria and parasites.[29] Infectious diarrhea is frequently referred to as gastroenteritis.[30] Norovirus is the most common cause of viral diarrhea in adults,[31] but rotavirus is the most common cause in children under five years old.[32] Adenovirus types 40 and 41,[33] and astroviruses cause a significant number of infections.[34] Shiga-toxin producing Escherichia coli, such as E coli o157:h7, are the most common cause of infectious bloody diarrhea in the United States.[35]
Campylobacter spp. are a common cause of bacterial diarrhea, but infections by Salmonella spp., Shigella spp. and some strains of Escherichia coli are also a frequent cause.[36]
In the elderly, particularly those who have been treated with antibiotics for unrelated infections, a toxin produced by Clostridioides difficile often causes severe diarrhea.[37]
Parasites, particularly protozoa e.g., Cryptosporidium spp., Giardia spp., Entamoeba histolytica, Blastocystis spp., Cyclospora cayetanensis, are frequently the cause of diarrhea that involves chronic infection. The broad-spectrum antiparasitic agent nitazoxanide has shown efficacy against many diarrhea-causing parasites.[38]
Other infectious agents, such as parasites or bacterial toxins, may exacerbate symptoms.[27] In sanitary living conditions where there is ample food and a supply of clean water, an otherwise healthy person usually recovers from viral infections in a few days. However, for ill or malnourished individuals, diarrhea can lead to severe dehydration and can become life-threatening.[39]
Sanitation
Poverty often leads to unhygienic living conditions, as in this community in the Indian Himalayas. Such conditions promote contraction of diarrheal diseases, as a result of poor sanitation and hygiene.
Open defecation is a leading cause of infectious diarrhea leading to death.[40]
Poverty is a good indicator of the rate of infectious diarrhea in a population. This association does not stem from poverty itself, but rather from the conditions under which impoverished people live. The absence of certain resources compromises the ability of the poor to defend themselves against infectious diarrhea. "Poverty is associated with poor housing, crowding, dirt floors, lack of access to clean water or to sanitary disposal of fecal waste (sanitation), cohabitation with domestic animals that may carry human pathogens, and a lack of refrigerated storage for food, all of which increase the frequency of diarrhea ... Poverty also restricts the ability to provide age-appropriate, nutritionally balanced diets or to modify diets when diarrhea develops so as to mitigate and repair nutrient losses. The impact is exacerbated by the lack of adequate, available, and affordable medical care."[41]
One of the most common causes of infectious diarrhea is a lack of clean water. Often, improper fecal disposal leads to contamination of groundwater. This can lead to widespread infection among a population, especially in the absence of water filtration or purification. Human feces contains a variety of potentially harmful human pathogens.[42]
Nutrition
may have more aggressive behavior with poorer prognosis, when compared to oral cancer in non-HSCT patients.[51]
A meta-analysis showed that the risk of secondary cancers such as bone cancer, head and neck cancers, and melanoma, with standardized incidence ratios of 10.04 (3.48–16.61), 6.35 (4.76–7.93), and 3.52 (2.65–4.39), respectively, was significantly increased after HSCT. So, diagnostic tests for these cancers should be included in the screening program of these patients for the prevention and early detection of these cancers.[52]
Prognosis
Prognosis in HSCT varies widely dependent upon disease type, stage, stem-cell source, HLA-matched status (for allogeneic HSCT), and conditioning regimen. A transplant offers a chance for cure or long-term remission if the inherent complications of graft versus host disease, immunosuppressive treatments and the spectrum of opportunistic infections can be survived.[31][32] In recent years, survival rates have been gradually improving across almost all populations and subpopulations receiving transplants.[53]
Mortality for allogeneic stem cell transplantation can be estimated using the prediction model created by Sorror et al.,[54] using the Hematopoietic Cell Transplantation-Specific Comorbidity Index (HCT-CI). The HCT-CI was derived and validated by investigators at the Fred Hutchinson Cancer Research Center in the U.S. The HCT-CI modifies and adds to a well-validated comorbidity index, the Charlson Comorbidity Index (CCI) (Charlson, et al.)[55] The CCI was previously applied to patients undergoing allogeneic HCT, but appears to provide less survival prediction and discrimination than the HCT-CI scoring system.
Patients who were successfully treated with HSCT and total body irradiation in childhood were found to have increased fat mass percentage, leading to significantly decreased exercise capacity in adulthood. This suggests patients who underwent successful treatment with HSCT have an increased predisposition to cardiovascular disease later in life.[56]
Risks to donor
The risks of a complication depend on patient characteristics, health care providers, and the apheresis procedure, and the colony-stimulating factor used (G-CSF). G-CSF drugs include filgrastim (Neupogen, Neulasta), and lenograstim (Graslopin).
Drug risks
Filgrastim is typically dosed in the 10 microgram/kg level for 4–5 days during the harvesting of stem cells. The documented adverse effects of filgrastim include splenic rupture, acute respiratory distress syndrome, alveolar hemorrhage, and allergic reactions (usually experienced in first 30 minutes).[57][58][59] In addition, platelet and hemoglobin levels dip postprocedurally, not returning to normal until after a month.[59]
The question of whether geriatrics (patients over 65) react the same as patients under 65 has not been sufficiently examined. Coagulation issues and inflammation of atherosclerotic plaques are known to occur as a result of G-CSF injection. G-CSF has also been described to induce genetic changes in agranulocytes of normal donors.[58] There is no statistically significant evidence either for or against the hypothesis that myelodysplasia (MDS) or acute myeloid leukaemia (AML) can be induced by G-CSF in susceptible individuals.[60]
Access risks
Blood is drawn from a peripheral vein in a majority of patients, but a central line to the jugular, subclavian, and femoral veins may be used. Adverse reactions during apheresis were experienced in 20% of women and 8% of men, these adverse events primarily consisted of numbness/tingling, multiple line attempts, and nausea.[59]
Clinical observations
A study involving 2,408 donors (aged 18–60 years) indicated that bone pain (primarily back and hips) as a result of filgrastim treatment is observed in 80% of donors.[59] Donation is not recommended for those with a history of back pain.[59] Other symptoms observed in more than 40 percent of donors include muscle pain, headache, fatigue, and difficulty sleeping.[59] These symptoms all returned to baseline 1 month after donation in the majority of patients.[59]
In one meta-study that incorporated data from 377 donors, 44% of patients reported having adverse side effects after peripheral blood HSCT.[60] Side effects included pain prior to the collection procedure as a result of G-CSF injections, and postprocedural generalized skeletal pain, fatigue, and reduced energy.[60]
Severe reactions
A study that surveyed 2,408 donors found that serious adverse events (requiring prolonged hospitalization) occurred in 15 donors (at a rate of 0.6%), although none of these events was fatal.[59] Donors were not observed to have higher than normal rates of cancer with up to 4–8 years of follow-up.[59] One study based on a survey of medical teams covered about 24,000 peripheral blood HSCT cases between 1993 and 2005, and found a serious cardiovascular adverse reaction rate of about one in 1,500.[58] This study reported a cardiovascular-related fatality risk within the first 30 days of HSCT of about two in 10,000.[58]
History
In 1939, a woman with aplastic anaemia received the first human bone marrow transfusion. This patient received regular blood transfusions, and an attempt was made to increase her leukocyte and platelet counts by intravenous bone marrow injection without unexpected reaction.[61]
Stem-cell transplantation was pioneered using bone marrow-derived stem cells by a team at the Fred Hutchinson Cancer Research Center from the 1950s through the 1970s led by E. Donnall Thomas, whose work was later recognized with a Nobel Prize in Physiology or Medicine. Thomas' work showed that bone-marrow cells infused intravenously could repopulate the bone marrow and produce new blood cells. His work also reduced the likelihood of developing a life-threatening graft-versus-host disease.[62] Collaborating with Eloise Giblett, a professor at the University of Washington, he discovered genetic markers that could confirm donor matches.
The first physician to perform a successful human bone-marrow transplant on a disease other than cancer was Robert A. Good at the University of Minnesota in 1968.[63] In 1975, John Kersey, also of the University of Minnesota, performed the first successful bone-marrow transplant to cure lymphoma. His patient, a 16-year-old-boy, is today the longest-living lymphoma transplant survivor.[64]
Donor registration and recruitment
At the end of 2012, 20.2 million people had registered their willingness to be a bone-marrow donor with one of the 67 registries from 49 countries participating in Bone Marrow Donors Worldwide. Around 17.9 million of these registered donors had been ABDR typed, allowing easy matching. A further 561,000 cord blood units had been received by one of 46 cord blood banks from 30 countries participating. The highest total number of bone-marrow donors registered were those from the U.S. (8.0 million), and the highest number per capita were those from Cyprus (15.4% of the population).[65]
Within the U.S., racial minority groups are the least likely to be registered, so are the least likely to find a potentially life-saving match. In 1990, only six African Americans were able to find a bone-marrow match, and all six had common European genetic signatures.[66]
Africans are more genetically diverse than people of European descent, which means that more registrations are needed to find a match. Bone marrow and cord blood banks exist in South Africa, and a new program is beginning in Nigeria.[66] Many people belonging to different races are requested to donate as a shortage of donors exists in African, mixed race, Latino, aboriginal, and many other communities.
Two registries in the U.S. recruit unrelated allogeneic donors: NMDP or Be the Match, and the Gift of Life Marrow Registry.
Research
HIV
In 2007, a team of doctors in Berlin, Germany, including Gero Hütter, performed a stem-cell transplant for leukemia patient Timothy Ray Brown, who was also HIV-positive.[67] From 60 matching donors, they selected a [CCR5]-Δ32 homozygous individual with two genetic copies of a rare variant of a cell surface receptor. This genetic trait confers resistance to HIV infection by blocking attachment of HIV to the cell. Roughly one in 1,000 people of European ancestry have this inherited mutation, but it is rarer in other populations.[68][69] The transplant was repeated a year later after a leukemia relapse. Over three years after the initial transplant, and despite discontinuing antiretroviral therapy, researchers cannot detect HIV in the transplant recipient's blood or in various biopsies of his tissues.[70] Levels of HIV-specific antibodies have also declined, leading to speculation that the patient may have been functionally cured of HIV, but scientists emphasise that this is an unusual case.[71] Potentially fatal transplant complications (the "Berlin patient" developed graft-versus-host disease and leukoencephalopathy) mean that the procedure could not be performed in others with HIV, even if sufficient numbers of suitable donors were found.[72][73]
In 2012, Daniel Kuritzkes reported results of two stem-cell transplants in patients with HIV. They did not, however, use donors with the Δ32 deletion. After their transplant procedures, both were put on antiretroviral therapies, during which neither showed traces of HIV in their blood plasma and purified CD4+ T cells using a sensitive culture method (less than 3 copies/ml). The virus was once again detected in both patients some time after the discontinuation of therapy.[74]
In 2019, a British man became the second to be cleared of HIV after receiving a bone-marrow transplant from a virus-resistant (Δ32) donor. This patient is being called "the London patient" (a reference to the famous Berlin patient).[75]
Multiple sclerosis
Since McAllister's 1997 report on a patient with multiple sclerosis (MS) who received a bone-marrow transplant for chronic myelogenous leukemia (CML),[76] over 600 reports have been published describing HSCTs performed primarily for MS.[77] These have been shown to "reduce or eliminate ongoing clinical relapses, halt further progression, and reduce the burden of disability in some patients" who have aggressive, highly active MS, "in the absence of chronic treatment with disease-modifying agents".[77] A randomized clinical trial including 110 patients showed that HSCT significantly prolonged time to disease progression compared to disease-modifying therapy.[78] Long-term outcome in patients with severe disease has showed that complete disease remission after HSCT is possible.[79]
Other autoimmune neurological diseases
HSCT can also be used for treating selected, severe cases of other autoimmune neurological diseases such as neuromyelitis optica, chronic inflammatory demyelinating polyneuropathy, and myasthenia gravis.[80]
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Allers K, Hütter G, Hofmann J, Loddenkemper C, Rieger K, Thiel E, Schneider T (March 2011). "Evidence for the cure of HIV infection by CCR5Δ32/Δ32 stem cell transplantation". Blood. 117 (10): 2791–2799. doi:10.1182/blood-2010-09-309591. PMID 21148083. S2CID 27285440.
"Transplanting Hope: Stem Cell Experiment Raises Eyebrows at CROI". aidsmeds.com. 11 March 2008. Archived from the original on 26 January 2016. Retrieved 2 May 2018.
Levy JA (February 2009). "Not an HIV cure, but encouraging new directions". The New England Journal of Medicine. 360 (7): 724–725. doi:10.1056/NEJMe0810248. PMID 19213687.
van Lunzen J, Fehse B, Hauber J (June 2011). "Gene therapy strategies: can we eradicate HIV?". Current HIV/AIDS Reports. 8 (2): 78–84. doi:10.1007/s11904-011-0073-9. PMID 21331536. S2CID 43463970.
"HIV returns in two Boston patients after bone marrow transplants". CNN. 9 December 2013. Archived from the original on 8 December 2013.
Mandavilli, Apoorva (4 March 2019). "H.I.V. Is Reported Cured in a Second Patient, a Milestone in the Global AIDS Epidemic". The New York Times.
McAllister LD, Beatty PG, Rose J (February 1997). "Allogeneic bone marrow transplant for chronic myelogenous leukemia in a patient with multiple sclerosis". Bone Marrow Transplantation. 19 (4): 395–397. doi:10.1038/sj.bmt.1700666. PMID 9051253.
Atkins HL, Freedman MS (January 2013). "Hematopoietic stem cell therapy for multiple sclerosis: top 10 lessons learned". Neurotherapeutics. 10 (1): 68–76. doi:10.1007/s13311-012-0162-5. PMC 3557353. PMID 23192675.
Burt RK, Balabanov R, Burman J, Sharrack B, Snowden JA, Oliveira MC, et al. (January 2019). "Effect of Nonmyeloablative Hematopoietic Stem Cell Transplantation vs Continued Disease-Modifying Therapy on Disease Progression in Patients With Relapsing-Remitting Multiple Sclerosis: A Randomized Clinical Trial". JAMA. 321 (2): 165–174. doi:10.1001/jama.2018.18743. PMC 6439765. PMID 30644983.
Tolf A, Fagius J, Carlson K, Åkerfeldt T, Granberg T, Larsson EM, Burman J (November 2019). "Sustained remission in multiple sclerosis after hematopoietic stem cell transplantation". Acta Neurologica Scandinavica. 140 (5): 320–327. doi:10.1111/ane.13147. PMID 31297793. S2CID 195894616.
Burman J, Tolf A, Hägglund H, Askmark H (February 2018). "Autologous haematopoietic stem cell transplantation for neurological diseases". Journal of Neurology, Neurosurgery, and Psychiatry. 89 (2): 147–155. doi:10.1136/jnnp-2017-316271. PMC 5800332. PMID 28866625.
Further reading
Cote GM, Hochberg EP, Muzikansky A, Hochberg FH, Drappatz J, McAfee SL, et al. (January 2012). "Autologous stem cell transplantation with thiotepa, busulfan, and cyclophosphamide (TBC) conditioning in patients with CNS involvement by non-Hodgkin lymphoma". Biology of Blood and Marrow Transplantation. 18 (1): 76–83. doi:10.1016/j.bbmt.2011.07.006. PMID 21749848.
External links
Wikimedia Commons has media related to Hematopoietic stem cell transplantation.
Bone marrow transplant – What happens on NHS Choices
HCT-CI (Sorror et al. 2005) online calculator
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Procedures relating to the haematopoetic and lymphatic systems
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From Wikipedia, the free encyclopedia
For other uses, see Disease (disambiguation). "Maladies" redirects here. For the 2012 film, see Maladies (film). "Ailment" redirects here. Not to be confused with Aliment.
"The Sick Girl", 1882, National Gallery of Denmark
A disease is a particular abnormal condition that adversely affects the structure or function of all or part of an organism and is not immediately due to any external injury.[1][2] Diseases are often known to be medical conditions that are associated with specific signs and symptoms. A disease may be caused by external factors such as pathogens or by internal dysfunctions. For example, internal dysfunctions of the immune system can produce a variety of different diseases, including various forms of immunodeficiency, hypersensitivity, allergies, and autoimmune disorders.
In humans, disease is often used more broadly to refer to any condition that causes pain, dysfunction, distress, social problems, or death to the person affected, or similar problems for those in contact with the person. In this broader sense, it sometimes includes injuries, disabilities, disorders, syndromes, infections, isolated symptoms, deviant behaviors, and atypical variations of structure and function, while in other contexts and for other purposes these may be considered distinguishable categories. Diseases can affect people not only physically but also mentally, as contracting and living with a disease can alter the affected person's perspective on life.
Death due to disease is called death by natural causes. There are four main types of disease: infectious diseases, deficiency diseases, hereditary diseases (including both genetic and non-genetic hereditary diseases), and physiological diseases. Diseases can also be classified in other ways, such as communicable versus non-communicable diseases. The deadliest diseases in humans are coronary artery disease (blood flow obstruction), followed by cerebrovascular disease and lower respiratory infections.[3] In developed countries, the diseases that cause the most sickness overall are neuropsychiatric conditions, such as depression and anxiety.
The study of disease is called pathology, which includes the study of etiology, or cause.
Terminology
Concepts
In many cases, terms such as disease, disorder, morbidity, sickness and illness are used interchangeably; however, there are situations when specific terms are considered preferable.[4]
Disease
The term disease broadly refers to any condition that impairs the normal functioning of the body. For this reason, diseases are associated with the dysfunction of the body's normal homeostatic processes.[5] Commonly, the term is used to refer specifically to infectious diseases, which are clinically evident diseases that result from the presence of pathogenic microbial agents, including viruses, bacteria, fungi, protozoa, multicellular organisms, and aberrant proteins known as prions. An infection or colonization that does not and will not produce clinically evident impairment of normal functioning, such as the presence of the normal bacteria and yeasts in the gut, or of a passenger virus, is not considered a disease. By contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease. Non-infectious diseases are all other diseases, including most forms of cancer, heart disease, and genetic disease.
Acquired disease
An acquired disease is one that began at some point during one's lifetime, as opposed to disease that was already present at birth, which is congenital disease. Acquired sounds like it could mean "caught via contagion", but it simply means acquired sometime after birth. It also sounds like it could imply secondary disease, but acquired disease can be primary disease.
Acute disease
An acute disease is one of a short-term nature (acute); the term sometimes also connotes a fulminant nature
Chronic condition or chronic disease
A chronic disease is one that persists over time, often for at least six months, but may also include illnesses that are expected to last for the entirety of one's natural life.
Congenital disorder or congenital disease
A congenital disorder is one that is present at birth. It is often a genetic disease or disorder and can be inherited. It can also be the result of a vertically transmitted infection from the mother, such as HIV/AIDS.
Genetic disease
A genetic disorder or disease is caused by one or more genetic mutations. It is often inherited, but some mutations are random and de novo.
Hereditary or inherited disease
A hereditary disease is a type of genetic disease caused by genetic mutations that are hereditary (and can run in families)
Iatrogenic disease
An iatrogenic disease or condition is one that is caused by medical intervention, whether as a side effect of a treatment or as an inadvertent outcome.
Idiopathic disease
An idiopathic disease has an unknown cause or source. As medical science has advanced, many diseases with entirely unknown causes have had some aspects of their sources explained and therefore shed their idiopathic status. For example, when germs were discovered, it became known that they were a cause of infection, but particular germs and diseases had not been linked. In another example, it is known that autoimmunity is the cause of some forms of diabetes mellitus type 1, even though the particular molecular pathways by which it works are not yet understood. It is also common to know certain factors are associated with certain diseases; however, association does not necessarily imply causality. For example, a third factor might be causing both the disease, and the associated phenomenon.
Incurable disease
A disease that cannot be cured. Incurable diseases are not necessarily terminal diseases, and sometimes a disease's symptoms can be treated sufficiently for the disease to have little or no impact on quality of life.
Primary disease
A primary disease is a disease that is due to a root cause of illness, as opposed to secondary disease, which is a sequela, or complication that is caused by the primary disease. For example, a common cold is a primary disease, where rhinitis is a possible secondary disease, or sequela. A doctor must determine what primary disease, a cold or bacterial infection, is causing a patient's secondary rhinitis when deciding whether or not to prescribe antibiotics.
Secondary disease
A secondary disease is a disease that is a sequela or complication of a prior, causal disease, which is referred to as the primary disease or simply the underlying cause (root cause). For example, a bacterial infection can be primary, wherein a healthy person is exposed to bacteria and becomes infected, or it can be secondary to a primary cause, that predisposes the body to infection. For example, a primary viral infection that weakens the immune system could lead to a secondary bacterial infection. Similarly, a primary burn that creates an open wound could provide an entry point for bacteria, and lead to a secondary bacterial infection.
Terminal disease
A terminal disease is one that is expected to have the inevitable result of death. Previously, AIDS was a terminal disease; it is now incurable, but can be managed indefinitely using medications.
Illness
The terms illness and sickness are both generally used as synonyms for disease; however, the term illness is occasionally used to refer specifically to the patient's personal experience of their disease.[6][7][8][9] In this model, it is possible for a person to have a disease without being ill (to have an objectively definable, but asymptomatic, medical condition, such as a subclinical infection, or to have a clinically apparent physical impairment but not feel sick or distressed by it), and to be ill without being diseased (such as when a person perceives a normal experience as a medical condition, or medicalizes a non-disease situation in their life – for example, a person who feels unwell as a result of embarrassment, and who interprets those feelings as sickness rather than normal emotions). Symptoms of illness are often not directly the result of infection, but a collection of evolved responses – sickness behavior by the body – that helps clear infection and promote recovery. Such aspects of illness can include lethargy, depression, loss of appetite, sleepiness, hyperalgesia, and inability to concentrate.[10][11][12]
Disorder
A disorder is a functional abnormality or disturbance that may or may not show specific signs and symptoms. Medical disorders can be categorized into mental disorders, physical disorders, genetic disorders, emotional and behavioral disorders, and functional disorders.[13] The term disorder is often considered more value-neutral and less stigmatizing than the terms disease or illness, and therefore is preferred terminology in some circumstances.[14] In mental health, the term mental disorder is used as a way of acknowledging the complex interaction of biological, social, and psychological factors in psychiatric conditions; however, the term disorder is also used in many other areas of medicine, primarily to identify physical disorders that are not caused by infectious organisms, such as metabolic disorders.
Medical condition or health condition
A medical condition or health condition is a broad concept that includes all diseases, lesions, disorders, or nonpathologic condition that normally receives medical treatment, such as pregnancy or childbirth. While the term medical condition generally includes mental illnesses, in some contexts the term is used specifically to denote any illness, injury, or disease except for mental illnesses. The Diagnostic and Statistical Manual of Mental Disorders (DSM), the widely used psychiatric manual that defines all mental disorders, uses the term general medical condition to refer to all diseases, illnesses, and injuries except for mental disorders.[15] This usage is also commonly seen in the psychiatric literature. Some health insurance policies also define a medical condition as any illness, injury, or disease except for psychiatric illnesses.[16]
As it is more value-neutral than terms like disease, the term medical condition is sometimes preferred by people with health issues that they do not consider deleterious. However, by emphasizing the medical nature of the condition, this term is sometimes rejected, such as by proponents of the autism rights movement.
The term medical condition is also a synonym for medical state, in which case it describes an individual patient's current state from a medical standpoint. This usage appears in statements that describe a patient as being in critical condition, for example.
Morbidity
Morbidity (from Latin morbidus 'sick, unhealthy') is a diseased state, disability, or poor health due to any cause.[17] The term may refer to the existence of any form of disease, or to the degree that the health condition affects the patient. Among severely ill patients, the level of morbidity is often measured by ICU scoring systems. Comorbidity, or co-existing disease, is the simultaneous presence of two or more medical conditions, such as schizophrenia and substance abuse.
In epidemiology and actuarial science, the term morbidity (also morbidity rate or morbidity frequency) can refer to either the incidence rate, the prevalence of a disease or medical condition, or the percentage of people who experience a given condition within a given timeframe (e.g., 20% of people will get influenza in a year).[18] This measure of sickness is contrasted with the mortality rate of a condition, which is the proportion of people dying during a given time interval. Morbidity rates are used in actuarial professions, such as health insurance, life insurance, and long-term care insurance, to determine the premiums charged to customers. Morbidity rates help insurers predict the likelihood that an insured will contract or develop any number of specified diseases.
Pathosis or pathology
Pathosis (plural pathoses) is synonymous with disease. The word pathology also has this sense, in which it is commonly used by physicians in the medical literature, although some editors prefer to reserve pathology to its other senses. Sometimes a slight connotative shade causes preference for pathology or pathosis implying "some [as yet poorly analyzed] pathophysiologic process" rather than disease implying "a specific disease entity as defined by diagnostic criteria being already met". This is hard to quantify denotatively, but it explains why cognitive synonymy is not invariable.
Syndrome
A syndrome is the association of several signs and symptoms, or other characteristics that often occur together, regardless of whether the cause is known. Some syndromes such as Down syndrome are known to have only one cause (an extra chromosome at birth). Others such as Parkinsonian syndrome are known to have multiple possible causes. Acute coronary syndrome, for example, is not a single disease itself but is rather the manifestation of any of several diseases including myocardial infarction secondary to coronary artery disease. In yet other syndromes, however, the cause is unknown. A familiar syndrome name often remains in use even after an underlying cause has been found or when there are a number of different possible primary causes. Examples of the first-mentioned type are that Turner syndrome and DiGeorge syndrome are still often called by the "syndrome" name despite that they can also be viewed as disease entities and not solely as sets of signs and symptoms.
Predisease
Predisease is a subclinical or prodromal vanguard of a disease. Prediabetes and prehypertension are common examples. The nosology or epistemology of predisease is contentious, though, because there is seldom a bright line differentiating a legitimate concern for subclinical or premonitory status and the conflict of interest–driven over-medicalization (e.g., by pharmaceutical manufacturers) or de-medicalization (e.g., by medical and disability insurers). Identifying legitimate predisease can result in useful preventive measures, such as motivating the person to get a healthy amount of physical exercise,[19] but labeling a healthy person with an unfounded notion of predisease can result in overtreatment, such as taking drugs that only help people with severe disease or paying for treatments with a poor benefit–cost ratio.
One review proposed three criteria for predisease:
a high risk for progression to disease making one "far more likely to develop" it than others are- for example, a pre-cancer will almost certainly turn into cancer over time
actionability for risk reduction – for example, removal of the precancerous tissue prevents it from turning into a potentially deadly cancer
benefit that outweighs the harm of any interventions taken – removing the precancerous tissue prevents cancer, and thus prevents a potential death from cancer.[20]
Types by body system
Mental
Mental illness is a broad, generic label for a category of illnesses that may include affective or emotional instability, behavioral dysregulation, cognitive dysfunction or impairment. Specific illnesses known as mental illnesses include major depression, generalized anxiety disorders, schizophrenia, and attention deficit hyperactivity disorder, to name a few. Mental illness can be of biological (e.g., anatomical, chemical, or genetic) or psychological (e.g., trauma or conflict) origin. It can impair the affected person's ability to work or study and can harm interpersonal relationships. The term insanity is used technically as a legal term.[citation needed]
Organic
An organic disease is one caused by a physical or physiological change to some tissue or organ of the body. The term sometimes excludes infections. It is commonly used in contrast with mental disorders. It includes emotional and behavioral disorders if they are due to changes to the physical structures or functioning of the body, such as after a stroke or a traumatic brain injury, but not if they are due to psychosocial issues.
Stages
In an infectious disease, the incubation period is the time between infection and the appearance of symptoms. The latency period is the time between infection and the ability of the disease to spread to another person, which may precede, follow, or be simultaneous with the appearance of symptoms. Some viruses also exhibit a dormant phase, called viral latency, in which the virus hides in the body in an inactive state. For example, varicella zoster virus causes chickenpox in the acute phase; after recovery from chickenpox, the virus may remain dormant in nerve cells for many years, and later cause herpes zoster (shingles).
Acute disease
An acute disease is a short-lived disease, like the common cold.
Chronic disease
A chronic disease is one that lasts for a long time, usually at least six months. During that time, it may be constantly present, or it may go into remission and periodically relapse. A chronic disease may be stable (does not get any worse) or it may be progressive (gets worse over time). Some chronic diseases can be permanently cured. Most chronic diseases can be beneficially treated, even if they cannot be permanently cured.
Clinical disease
One that has clinical consequences; in other words, the stage of the disease that produces the characteristic signs and symptoms of that disease.[21] AIDS is the clinical disease stage of HIV infection.
Cure
A cure is the end of a medical condition or a treatment that is very likely to end it, while remission refers to the disappearance, possibly temporarily, of symptoms. Complete remission is the best possible outcome for incurable diseases.
Flare-up
"Flareup" redirects here. For the Transformers character, see Flareup (Transformers).
See also: Exacerbation
A flare-up can refer to either the recurrence of symptoms or an onset of more severe symptoms.[22]
Progressive disease
Progressive disease is a disease whose typical natural course is the worsening of the disease until death, serious debility, or organ failure occurs. Slowly progressive diseases are also chronic diseases; many are also degenerative diseases. The opposite of progressive disease is stable disease or static disease: a medical condition that exists, but does not get better or worse.
Refractory disease
A refractory disease is a disease that resists treatment, especially an individual case that resists treatment more than is normal for the specific disease in question.
Subclinical disease
Also called silent disease, silent stage, or asymptomatic disease. This is a stage in some diseases before the symptoms are first noted.[23]
Terminal phase
If a person will die soon from a disease, regardless of whether that disease typically causes death, then the stage between the earlier disease process and active dying is the terminal phase.
Recovery
See also: Convalescence and Recuperation
Recovery can refer to the repairing of physical processes (tissues, organs etc.) and the resumption of healthy functioning after damage causing processes have been cured.
Extent
skin rash on the leg
This rash only affects one part of the body, so it is a localized disease.
Localized disease
A localized disease is one that affects only one part of the body, such as athlete's foot or an eye infection.
Disseminated disease
A disseminated disease has spread to other parts; with cancer, this is usually called metastatic disease.
Systemic disease
A systemic disease is a disease that affects the entire body, such as influenza or high blood pressure.
Classification
Main articles: Nosology and Medical classification
Diseases may be classified by cause, pathogenesis (mechanism by which the disease is caused), or by symptoms. Alternatively, diseases may be classified according to the organ system involved, though this is often complicated since many diseases affect more than one organ.
A chief difficulty in nosology is that diseases often cannot be defined and classified clearly, especially when cause or pathogenesis are unknown. Thus diagnostic terms often only reflect a symptom or set of symptoms (syndrome).
Classical classification of human disease derives from the observational correlation between pathological analysis and clinical syndromes. Today it is preferred to classify them by their cause if it is known.[24]
The most known and used classification of diseases is the World Health Organization's ICD. This is periodically updated. Currently, the last publication is the ICD-11.
Causes
See also: Cause (medicine) and Transmission (medicine)
Diseases can be caused by any number of factors and may be acquired or congenital. Microorganisms, genetics, the environment or a combination of these can contribute to a diseased state.[25]
Only some diseases such as influenza are contagious and commonly believed infectious. The microorganisms that cause these diseases are known as pathogens and include varieties of bacteria, viruses, protozoa, and fungi. Infectious diseases can be transmitted, e.g. by hand-to-mouth contact with infectious material on surfaces, by bites of insects or other carriers of the disease, and from contaminated water or food (often via fecal contamination), etc.[26] Also, there are sexually transmitted diseases. In some cases, microorganisms that are not readily spread from person to person play a role, while other diseases can be prevented or ameliorated with appropriate nutrition or other lifestyle changes.
Some diseases, such as most (but not all) forms of cancer, heart disease, and mental disorders, are non-infectious diseases. Many non-infectious diseases have a partly or completely genetic basis (see genetic disorder) and may thus be transmitted from one generation to another.
Social determinants of health are the social conditions in which people live that determine their health. Illnesses are generally related to social, economic, political, and environmental circumstances.[27] Social determinants of health have been recognized by several health organizations such as the Public Health Agency of Canada and the World Health Organization to greatly influence collective and personal well-being. The World Health Organization's Social Determinants Council also recognizes Social determinants of health in poverty.
When the cause of a disease is poorly understood, societies tend to mythologize the disease or use it as a metaphor or symbol of whatever that culture considers evil. For example, until the bacterial cause of tuberculosis was discovered in 1882, experts variously ascribed the disease to heredity, a sedentary lifestyle, depressed mood, and overindulgence in sex, rich food, or alcohol, all of which were social ills at the time.[28]
When a disease is caused by a pathogenic organism (e.g., when malaria is caused by Plasmodium), one should not confuse the pathogen (the cause of the disease) with disease itself. For example, West Nile virus (the pathogen) causes West Nile fever (the disease). The misuse of basic definitions in epidemiology is frequent in scientific publications.[29]
Types of causes
A child rides a bicycle. An adult and a child walk a dog along a path in a green park..
Regular physical activity, such as riding a bicycle or walking, reduces the risk of lifestyle diseases.
Airborne
An airborne disease is any disease that is caused by pathogens and transmitted through the air.[30]
Foodborne
Foodborne illness or food poisoning is any illness resulting from the consumption of food contaminated with pathogenic bacteria, toxins, viruses, prions or parasites.[31]
Infectious
Infectious diseases, also known as transmissible diseases or communicable diseases, comprise clinically evident illness (i.e., characteristic medical signs or symptoms of disease) resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism.[32] Included in this category are contagious diseases – an infection, such as influenza or the common cold, that commonly spreads from one person to another – and communicable diseases – a disease that can spread from one person to another, but does not necessarily spread through everyday contact.
Lifestyle
A lifestyle disease is any disease that appears to increase in frequency as countries become more industrialized and people live longer, especially if the risk factors include behavioral choices like a sedentary lifestyle or a diet high in unhealthful foods such as refined carbohydrates, trans fats, or alcoholic beverages.[33]
Non-communicable
A non-communicable disease is a medical condition or disease that is non-transmissible.[34] Non-communicable diseases cannot be spread directly from one person to another. Heart disease and cancer are examples of non-communicable diseases in humans.[35]
Prevention
Main article: Preventive medicine
Many diseases and disorders can be prevented through a variety of means. These include sanitation, proper nutrition, adequate exercise, vaccinations and other self-care and public health measures, such as obligatory face mask mandates[citation needed].
Treatments
Main article: Therapy
Medical therapies or treatments are efforts to cure or improve a disease or other health problems. In the medical field, therapy is synonymous with the word treatment. Among psychologists, the term may refer specifically to psychotherapy or "talk therapy". Common treatments include medications, surgery, medical devices, and self-care. Treatments may be provided by an organized health care system, or informally, by the patient or family members.
Preventive healthcare is a way to avoid an injury, sickness, or disease in the first place. A treatment or cure is applied after a medical problem has already started. A treatment attempts to improve or remove a problem, but treatments may not produce permanent cures, especially in chronic diseases. Cures are a subset of treatments that reverse diseases completely or end medical problems permanently. Many diseases that cannot be completely cured are still treatable. Pain management (also called pain medicine) is that branch of medicine employing an interdisciplinary approach to the relief of pain and improvement in the quality of life of those living with pain.[36]
Treatment for medical emergencies must be provided promptly, often through an emergency department or, in less critical situations, through an urgent care facility.
Epidemiology
Main article: Epidemiology
Epidemiology is the study of the factors that cause or encourage diseases. Some diseases are more common in certain geographic areas, among people with certain genetic or socioeconomic characteristics, or at different times of the year.
Epidemiology is considered a cornerstone methodology of public health research and is highly regarded in evidence-based medicine for identifying risk factors for diseases. In the study of communicable and non-communicable diseases, the work of epidemiologists ranges from outbreak investigation to study design, data collection, and analysis including the development of statistical models to test hypotheses and the documentation of results for submission to peer-reviewed journals. Epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic. Epidemiologists rely on a number of other scientific disciplines such as biology (to better understand disease processes), biostatistics (the current raw information available), Geographic Information Science (to store data and map disease patterns) and social science disciplines (to better understand proximate and distal risk factors). Epidemiology can help identify causes as well as guide prevention efforts.
In studying diseases, epidemiology faces the challenge of defining them. Especially for poorly understood diseases, different groups might use significantly different definitions. Without an agreed-on definition, different researchers may report different numbers of cases and characteristics of the disease.[37]
Some morbidity databases are compiled with data supplied by states and territories health authorities, at national levels[38][39] or larger scale (such as European Hospital Morbidity Database (HMDB))[40] which may contain hospital discharge data by detailed diagnosis, age and sex. The European HMDB data was submitted by European countries to the World Health Organization Regional Office for Europe.
Burdens of disease
Disease burden is the impact of a health problem in an area measured by financial cost, mortality, morbidity, or other indicators.
There are several measures used to quantify the burden imposed by diseases on people. The years of potential life lost (YPLL) is a simple estimate of the number of years that a person's life was shortened due to a disease. For example, if a person dies at the age of 65 from a disease, and would probably have lived until age 80 without that disease, then that disease has caused a loss of 15 years of potential life. YPLL measurements do not account for how disabled a person is before dying, so the measurement treats a person who dies suddenly and a person who died at the same age after decades of illness as equivalent. In 2004, the World Health Organization calculated that 932 million years of potential life were lost to premature death.[41]
The quality-adjusted life year (QALY) and disability-adjusted life year (DALY) metrics are similar but take into account whether the person was healthy after diagnosis. In addition to the number of years lost due to premature death, these measurements add part of the years lost to being sick. Unlike YPLL, these measurements show the burden imposed on people who are very sick, but who live a normal lifespan. A disease that has high morbidity, but low mortality, has a high DALY and a low YPLL. In 2004, the World Health Organization calculated that 1.5 billion disability-adjusted life years were lost to disease and injury.[41] In the developed world, heart disease and stroke cause the most loss of life, but neuropsychiatric conditions like major depressive disorder cause the most years lost to being sick.
Disease category Percent of all YPLLs lost, worldwide[41] Percent of all DALYs lost, worldwide[41] Percent of all YPLLs lost, Europe[41] Percent of all DALYs lost, Europe[41] Percent of all YPLLs lost, US and Canada[41] Percent of all DALYs lost, US and Canada[41]
Infectious and parasitic diseases, especially lower respiratory tract infections, diarrhea, AIDS, tuberculosis, and malaria 37% 26% 9% 6% 5% 3%
Neuropsychiatric conditions, e.g. depression 2% 13% 3% 19% 5% 28%
Injuries, especially motor vehicle accidents 14% 12% 18% 13% 18% 10%
Cardiovascular diseases, principally heart attacks and stroke 14% 10% 35% 23% 26% 14%
Premature birth and other perinatal deaths 11% 8% 4% 2% 3% 2%
Cancer 8% 5% 19% 11% 25% 13%
Society and culture
Obesity was a status symbol in Renaissance culture: "The Tuscan General Alessandro del Borro", attributed to Andrea Sacchi, 1645.[42] It is now generally regarded as a disease.
How a society responds to diseases is the subject of medical sociology.
A condition may be considered a disease in some cultures or eras but not in others. For example, obesity can represent wealth and abundance, and is a status symbol in famine-prone areas and some places hard-hit by HIV/AIDS.[43] Epilepsy is considered a sign of spiritual gifts among the Hmong people.[44]
Sickness confers the social legitimization of certain benefits, such as illness benefits, work avoidance, and being looked after by others. The person who is sick takes on a social role called the sick role. A person who responds to a dreaded disease, such as cancer, in a culturally acceptable fashion may be publicly and privately honored with higher social status.[45] In return for these benefits, the sick person is obligated to seek treatment and work to become well once more. As a comparison, consider pregnancy, which is not interpreted as a disease or sickness, even if the mother and baby may both benefit from medical care.
Most religions grant exceptions from religious duties to people who are sick. For example, one whose life would be endangered by fasting on Yom Kippur or during the month of Ramadan is exempted from the requirement, or even forbidden from participating.[46][47] People who are sick are also exempted from social duties. For example, ill health is the only socially acceptable reason for an American to refuse an invitation to the White House.[48]
The identification of a condition as a disease, rather than as simply a variation of human structure or function, can have significant social or economic implications. The controversial recognition of diseases such as repetitive stress injury (RSI) and post-traumatic stress disorder (PTSD) has had a number of positive and negative effects on the financial and other responsibilities of governments, corporations, and institutions towards individuals, as well as on the individuals themselves. The social implication of viewing aging as a disease could be profound, though this classification is not yet widespread.
Lepers were people who were historically shunned because they had an infectious disease, and the term "leper" still evokes social stigma. Fear of disease can still be a widespread social phenomenon, though not all diseases evoke extreme social stigma.
Social standing and economic status affect health. Diseases of poverty are diseases that are associated with poverty and low social status; diseases of affluence are diseases that are associated with high social and economic status. Which diseases are associated with which states vary according to time, place, and technology. Some diseases, such as diabetes mellitus, may be associated with both poverty (poor food choices) and affluence (long lifespans and sedentary lifestyles), through different mechanisms. The term lifestyle diseases describes diseases associated with longevity and that are more common among older people. For example, cancer is far more common in societies in which most members live until they reach the age of 80 than in societies in which most members die before they reach the age of 50.
Language of disease
An illness narrative is a way of organizing a medical experience into a coherent story that illustrates the sick individual's personal experience.
People use metaphors to make sense of their experiences with disease. The metaphors move disease from an objective thing that exists to an affective experience. The most popular metaphors draw on military concepts: Disease is an enemy that must be feared, fought, battled, and routed. The patient or the healthcare provider is a warrior, rather than a passive victim or bystander. The agents of communicable diseases are invaders; non-communicable diseases constitute internal insurrection or civil war. Because the threat is urgent, perhaps a matter of life and death, unthinkably radical, even oppressive, measures are society's and the patient's moral duty as they courageously mobilize to struggle against destruction. The War on Cancer is an example of this metaphorical use of language.[49] This language is empowering to some patients, but leaves others feeling like they are failures.[50]
Another class of metaphors describes the experience of illness as a journey: The person travels to or from a place of disease, and changes himself, discovers new information, or increases his experience along the way. He may travel "on the road to recovery" or make changes to "get on the right track" or choose "pathways".[49][50] Some are explicitly immigration-themed: the patient has been exiled from the home territory of health to the land of the ill, changing identity and relationships in the process.[51] This language is more common among British healthcare professionals than the language of physical aggression.[50]
Some metaphors are disease-specific. Slavery is a common metaphor for addictions: The alcoholic is enslaved by drink, and the smoker is captive to nicotine. Some cancer patients treat the loss of their hair from chemotherapy as a metonymy or metaphor for all the losses caused by the disease.[49]
Some diseases are used as metaphors for social ills: "Cancer" is a common description for anything that is endemic and destructive in society, such as poverty, injustice, or racism. AIDS was seen as a divine judgment for moral decadence, and only by purging itself from the "pollution" of the "invader" could society become healthy again.[49] More recently, when AIDS seemed less threatening, this type of emotive language was applied to avian flu and type 2 diabetes mellitus.[52] Authors in the 19th century commonly used tuberculosis as a symbol and a metaphor for transcendence. People with the disease were portrayed in literature as having risen above daily life to become ephemeral objects of spiritual or artistic achievement. In the 20th century, after its cause was better understood, the same disease became the emblem of poverty, squalor, and other social problems.[51]
See also
icon Medicine portal
icon Biology portal
Cryptogenic disease, a disease whose cause is currently unknown
Developmental disability, severe, lifelong disabilities attributable to mental or physical impairments
Environmental disease
Host–pathogen interaction
Lists of diseases
Mitochondrial disease
Philosophy of medicine
Plant pathology
Rare disease, a disease that affects very few people
Sociology of health and illness
Syndrome
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"Man and Disease", BBC Radio 4 discussion with Anne Hardy, David Bradley & Chris Dye (In Our Time, 15 December 2002)
CTD The Comparative Toxicogenomics Database is a scientific resource connecting chemicals, genes, and human diseases.
Free online health-risk assessment by Your Disease Risk at Washington University in St. Louis
Health Topics A–Z, fact sheets about many common diseases at the Centers for Disease Control
Health Topics, MedlinePlus descriptions of most diseases, with access to current research articles.
NLM Comprehensive database from the US National Library of Medicine
OMIM Comprehensive information on genes that cause disease at Online Mendelian Inheritance in Man
Report: The global burden of disease from the World Health Organization (WHO), 2004
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From Wikipedia, the free encyclopedia
For other uses, see Pathogen (disambiguation).
In biology, a pathogen (Greek: πάθος, pathos "suffering", "passion" and -γενής, -genēs "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.[1]
The term pathogen came into use in the 1880s.[2][3] Typically, the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus.[4][5][6] Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens.[7] The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called microbiology, while parasitology refers to the scientific study of parasites and the organisms that host them.
There are several pathways through which pathogens can invade a host. The principal pathways have different episodic time frames, but soil has the longest or most persistent potential for harboring a pathogen.
Diseases in humans that are caused by infectious agents are known as pathogenic diseases. Not all diseases are caused by pathogens, such as black lung from exposure to the pollutant coal dust, genetic disorders like sickle cell disease, and autoimmune diseases like lupus.
Pathogenicity
Pathogenicity is the potential disease-causing capacity of pathogens, involving a combination of infectivity (pathogen's ability to infect hosts) and virulence (severity of host disease). Koch's postulates are used to establish causal relationships between microbial pathogens and diseases. Whereas meningitis can be caused by a variety of bacterial, viral, fungal, and parasitic pathogens, cholera is only caused by some strains of Vibrio cholerae. Additionally, some pathogens may only cause disease in hosts with an immunodeficiency. These opportunistic infections often involve hospital-acquired infections among patients already combating another condition.[8]
Infectivity involves pathogen transmission through direct contact with the bodily fluids or airborne droplets of infected hosts, indirect contact involving contaminated areas/items, or transfer by living vectors like mosquitos and ticks. The basic reproduction number of an infection is the expected number of subsequent cases it is likely to cause through transmission.[9]
Virulence involves pathogens extracting host nutrients for their survival, evading host immune systems by producing microbial toxins and causing immunosuppression. Optimal virulence describes a theorized equilibrium between a pathogen spreading to additional hosts to parasitize resources, while lowering their virulence to keep hosts living for vertical transmission to their offspring.[10]
Types
Algae
Main article: Algae
Algae are single-celled eukaryotes that are generally non-pathogenic. Green algae from the genus Prototheca lack chlorophyll and are known to cause the disease protothecosis in humans, dogs, cats, and cattle, typically involving the soil-associated species Prototheca wickerhami.[11][12][13]
Bacteria
Main article: Pathogenic bacteria
Bacteria are single-celled prokaryotes that range in size from 0.15 and 700 μM.[14] While the vast majority are either harmless or beneficial to their hosts, such as members of the human gut microbiome that support digestion, a small percentage are pathogenic and cause infectious diseases. Bacterial virulence factors include adherence factors to attach to host cells, invasion factors supporting entry into host cells, capsules to prevent opsonization and phagocytosis, toxins, and siderophores to acquire iron.[15]
A photomicrograph of a stool that has shigella dysentery. These bacteria typically cause foodborne illness.
The bacterial disease tuberculosis, primarily caused by Mycobacterium tuberculosis, has one of the highest disease burdens, killing 1.6 million people in 2021, mostly in Africa and Southeast Asia.[16] Bacterial pneumonia is primarily caused by Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae, and Haemophilus influenzae.[17] Foodborne illnesses typically involve Campylobacter, Clostridium perfringens, Escherichia coli, Listeria monocytogenes, and Salmonella.[18] Other infectious diseases caused by pathogenic bacteria include tetanus, typhoid fever, diphtheria, and leprosy.[15]
Fungi
Main article: Pathogenic fungi
Fungi are eukaryotic organisms that can function as pathogens. There are approximately 300 known fungi that are pathogenic to humans, including Candida albicans, which is the most common cause of thrush, and Cryptococcus neoformans, which can cause a severe form of meningitis.[19] Typical fungal spores are 4.7 μm long or smaller.[20]
Prions
Main article: Prion
Magnified 100× and stained. This photomicrograph of the brain tissue shows the presence of the prominent spongiotic changes in the cortex, with the loss of neurons in a case of a variant of Creutzfeldt-Jakob disease (vCJD)
Prions are misfolded proteins that transmit their abnormal folding pattern to other copies of the protein without using nucleic acids. Besides obtaining prions from others, these misfolded proteins arise from genetic differences, either due to family history or sporadic mutations.[21] Plants uptake prions from contaminated soil and transport them into their stem and leaves, potentially transmitting the prions to herbivorous animals.[22] Additionally, wood, rocks, plastic, glass, cement, stainless steel, and aluminum have been shown binding, retaining, and releasing prions, showcasing that the proteins resist environmental degradation.[23]
Prions are best known for causing transmissible spongiform encephalopathy (TSE) diseases like Creutzfeldt–Jakob disease (CJD), variant Creutzfeldt–Jakob disease (vCJD), Gerstmann–Sträussler–Scheinker syndrome (GSS), fatal familial insomnia (FFI), and kuru in humans.[24]
While prions are typically viewed as pathogens that cause protein amyloid fibers to accumulate into neurodegenerative plaques, Susan Lindquist led research showing that yeast use prions to pass on evolutionarily beneficial traits.[25]
Viroids
Main article: Viroids
Not to be confused with virusoids or viruses, viroids are the smallest known infectious pathogens. Viroids are small single-stranded, circular RNA that are only known to cause plant diseases, such as the potato spindle tuber viroid that affects various agricultural crops. Viroid RNA is not protected by a protein coat, and it does not encode any proteins, only acting as a ribozyme to catalyze other biochemical reactions.[26]
Viruses
Main article: Virus
Viruses are generally between 20-200 nm in diameter.[27] For survival and replication, viruses inject their genome into host cells, insert those genes into the host genome, and hijack the host's machinery to produce hundreds of new viruses until the cell bursts open to release them for additional infections. The lytic cycle describes this active state of rapidly killing hosts, while the lysogenic cycle describes potentially hundreds of years of dormancy while integrated in the host genome.[28] Alongside the taxonomy organized by the International Committee on Taxonomy of Viruses (ICTV), the Baltimore classification separates viruses by seven classes of mRNA production:[29]
I: dsDNA viruses (e.g., Adenoviruses, Herpesviruses, and Poxviruses) cause herpes, chickenpox, and smallpox
II: ssDNA viruses (+ strand or "sense") DNA (e.g., Parvoviruses) include parvovirus B19
III: dsRNA viruses (e.g., Reoviruses) include rotaviruses
IV: (+)ssRNA viruses (+ strand or sense) RNA (e.g., Coronaviruses, Picornaviruses, and Togaviruses) cause COVID-19, dengue fever, Hepatitis A, Hepatitis C, rubella, and yellow fever
V: (−)ssRNA viruses (− strand or antisense) RNA (e.g., Orthomyxoviruses and Rhabdoviruses) cause ebola, influenza, measles, mumps, and rabies
VI: ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g., Retroviruses) cause HIV/AIDS
VII: dsDNA-RT viruses DNA with RNA intermediate in life-cycle (e.g., Hepadnaviruses) cause Hepatitis B
Other parasites
Main article: Human parasites
Two pinworms next to a ruler, measuring 6 millimeters in length
Protozoans are single-celled eukaryotes that feed on microorganisms and organic tissues. Many protozoans act as pathogenic parasites to cause diseases like malaria, amoebiasis, giardiasis, toxoplasmosis, cryptosporidiosis, trichomoniasis, Chagas disease, leishmaniasis, African trypanosomiasis (sleeping sickness), Acanthamoeba keratitis, and primary amoebic meningoencephalitis (naegleriasis).[30]
Parasitic worms (helminths) are macroparasites that can be seen by the naked eye. Worms live and feed in their living host, acquiring nutrients and shelter in the digestive tract or bloodstream of their host. They also manipulate the host's immune system by secreting immunomodulatory products which allows them to live in their host for years.[31] Helminthiasis is the generalized term for parasitic worm infections, which typically involve roundworms, tapeworms, and flatworms.[32]
Pathogen hosts
Bacteria
While bacteria are typically viewed as pathogens, they serve as hosts to bacteriophage viruses (commonly known as phages). The bacteriophage life cycle involves the viruses injecting their genome into bacterial cells, inserting those genes into the bacterial genome, and hijacking the bacteria's machinery to produce hundreds of new phages until the cell bursts open to release them for additional infections. Typically, bacteriophages are only capable of infecting a specific species or strain.[33]
Streptococcus pyogenes uses a Cas9 nuclease to cleave foreign DNA matching the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) associated with bacteriophages, removing the viral genes to avoid infection. This mechanism has been modified for artificial CRISPR gene editing.[34]
Plants
Plants can play host to a wide range of pathogen types, including viruses, bacteria, fungi, nematodes, and even other plants.[35] Notable plant viruses include the papaya ringspot virus, which has caused millions of dollars of damage to farmers in Hawaii and Southeast Asia,[36] and the tobacco mosaic virus which caused scientist Martinus Beijerinck to coin the term "virus" in 1898.[37] Bacterial plant pathogens cause leaf spots, blight, and rot in many plant species.[38] The most common bacterial pathogens for plants are Pseudomonas syringae and Ralstonia solanacearum, which cause leaf browning and other issues in potatoes, tomatoes, and bananas.[38]
Brown rot fungal disease on an apple. Brown rot typically target a variety of top-fruits.
Fungi are another major pathogen type for plants. They can cause a wide variety of issues such as shorter plant height, growths or pits on tree trunks, root or seed rot, and leaf spots.[39] Common and serious plant fungi include the rice blast fungus, Dutch elm disease, chestnut blight and the black knot and brown rot diseases of cherries, plums, and peaches. It is estimated that pathogenic fungi alone cause up to a 65% reduction in crop yield.[38]
Overall, plants have a wide array of pathogens and it has been estimated that only 3% of the disease caused by plant pathogens can be managed.[38]
Animals
Animals often get infected with many of the same or similar pathogens as humans including prions, viruses, bacteria, and fungi. While wild animals often get illnesses, the larger danger is for livestock animals. It is estimated that in rural settings, 90% or more of livestock deaths can be attributed to pathogens.[40][41] Animal transmissible spongiform encephalopathy (TSEs) involving prions include bovine spongiform encephalopathy (mad cow disease), chronic wasting disease, scrapie, transmissible mink encephalopathy, feline spongiform encephalopathy, and ungulate spongiform encephalopathy.[24][42] Other animal diseases include a variety of immunodeficiency disorders caused by viruses related to human immunodeficiency virus (HIV), such as BIV and FIV.[43]
Humans
Main article: Human pathogen
Humans can be infected with many types of pathogens, including prions, viruses, bacteria, and fungi, causing symptoms like sneezing, coughing, fever, vomiting, and potentially lethal organ failure. While some symptoms are caused by the pathogenic infection, others are caused by the immune system's efforts to kill the pathogen, such as feverishly high body temperatures meant to denature pathogenic cells.[4]
Treatment
Prions
Despite many attempts, no therapy has been shown to halt the progression of prion diseases.[44]
Viruses
A variety of prevention and treatment options exist for some viral pathogens. Vaccines are one common and effective preventive measure against a variety of viral pathogens.[45] Vaccines prime the immune system of the host, so that when the potential host encounters the virus in the wild, the immune system can defend against infection quickly. Vaccines designed against viruses include annual influenza vaccines and the two-dose MMR vaccine against measles, mumps, and rubella.[46] Vaccines are not available against the viruses responsible for HIV/AIDS, dengue, and chikungunya.[47]
Treatment of viral infections often involves treating the symptoms of the infection, rather than providing medication to combat the viral pathogen itself.[48][49] Treating the symptoms of a viral infection gives the host immune system time to develop antibodies against the viral pathogen. However, for HIV, highly active antiretroviral therapy (HAART) is conducted to prevent the viral disease from progressing into AIDS as immune cells are lost.[50]
Bacteria
A structure of Doxycycline a tetracycline-class antibiotic
Much like viral pathogens, infection by certain bacterial pathogens can be prevented via vaccines.[46] Vaccines against bacterial pathogens include the anthrax vaccine and pneumococcal vaccine. Many other bacterial pathogens lack vaccines as a preventive measure, but infection by these bacteria can often be treated or prevented with antibiotics. Common antibiotics include amoxicillin, ciprofloxacin, and doxycycline. Each antibiotic has different bacteria that it is effective against and has different mechanisms to kill that bacteria. For example, doxycycline inhibits the synthesis of new proteins in both gram-negative and gram-positive bacteria, which makes it a broad-spectrum antibiotic capable of killing most bacterial species.[51]
Due to misuse of antibiotics, such as prematurely ended prescriptions exposing bacteria to evolutionary pressure under sublethal doses, some bacterial pathogens have developed antibiotic resistance.[52] For example, a genetically distinct strain of Staphylococcus aureus called MRSA is resistant to the commonly prescribed beta-lactam antibiotics. A 2013 report from the Centers for Disease Control and Prevention (CDC) estimated that in the United States, at least 2 million people get an antibiotic-resistant bacterial infection annually, with at least 23,000 of those patients dying from the infection.[53]
Due to their indispensability in combating bacteria, new antibiotics are required for medical care. One target for new antimicrobial medications involves inhibiting DNA methyltransferases, as these proteins control the levels of expression for other genes, such as those encoding virulence factors.[54][55]
Fungi
Infection by fungal pathogens is treated with anti-fungal medication. Athlete's foot, jock itch, and ringworm are fungal skin infections that are treated with topical anti-fungal medications like clotrimazole.[56] Infections involving the yeast species Candida albicans cause oral thrush and vaginal yeast infections. These internal infections can either be treated with anti-fungal creams or with oral medication. Common anti-fungal drugs for internal infections include the echinocandin family of drugs and fluconazole.[57]
Algae
While algae are commonly not thought of as pathogens, the genus Prototheca causes disease in humans.[58][13] Treatment for protothecosis is currently under investigation, and there is no consistency in clinical treatment.[13]
Sexual interactions
Many pathogens are capable of sexual interaction. Among pathogenic bacteria, sexual interaction occurs between cells of the same species by the process of genetic transformation. Transformation involves the transfer of DNA from a donor cell to a recipient cell and the integration of the donor DNA into the recipient genome through genetic recombination. The bacterial pathogens Helicobacter pylori, Haemophilus influenzae, Legionella pneumophila, Neisseria gonorrhoeae, and Streptococcus pneumoniae frequently undergo transformation to modify their genome for additional traits and evasion of host immune cells.[59]
Eukaryotic pathogens are often capable of sexual interaction by a process involving meiosis and fertilization. Meiosis involves the intimate pairing of homologous chromosomes and recombination between them. Examples of eukaryotic pathogens capable of sex include the protozoan parasites Plasmodium falciparum, Toxoplasma gondii, Trypanosoma brucei, Giardia intestinalis, and the fungi Aspergillus fumigatus, Candida albicans and Cryptococcus neoformans.[59]
Viruses may also undergo sexual interaction when two or more viral genomes enter the same host cell. This process involves pairing of homologous genomes and recombination between them by a process referred to as multiplicity reactivation. The herpes simplex virus, human immunodeficiency virus, and vaccinia virus undergo this form of sexual interaction.[59]
These processes of sexual recombination between homologous genomes supports repairs to genetic damage caused by environmental stressors and host immune systems.[60]
See also
icon Biology portal
icon Medicine portal
Antigenic escape
Ecological competence
Emerging Pathogens Institute
Human pathogen
Pathogen-Host Interaction Database (PHI-base)
References
Thomas L (September 1972). "Germs". The New England Journal of Medicine. 287 (11): 553–5. doi:10.1056/NEJM197209142871109. PMID 5050429.
"Pathogen". Dictionary.com Unabridged (Online). n.d. Retrieved August 17, 2013.
Casadevall A, Pirofski LA (December 2014). "Microbiology: Ditch the term pathogen". Comment. Nature (paper). 516 (7530): 165–6. Bibcode:2014Natur.516..165C. doi:10.1038/516165a. PMID 25503219.
Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). "Introduction to Pathogens". Molecular Biology of the Cell (4th ed.). Garland Science.
"MetaPathogen – about various types of pathogenic organisms". Archived from the original on 5 October 2017. Retrieved 15 January 2015.
"Bacteria". Basic Biology. 18 March 2016.
Gazzinelli-Guimaraes PH, Nutman TB (2018). "Helminth parasites and immune regulation". F1000Research. 7: 1685. doi:10.12688/f1000research.15596.1. PMC 6206608. PMID 30416709.
Thomas, Stephen R.; Elkinton, Joseph S. (2004-03-01). "Pathogenicity and virulence". Journal of Invertebrate Pathology. 85 (3): 146–151. doi:10.1016/j.jip.2004.01.006. ISSN 0022-2011. PMID 15109897.
van den Driessche, Pauline (2017-08-01). "Reproduction numbers of infectious disease models". Infectious Disease Modelling. 2 (3): 288–303. doi:10.1016/j.idm.2017.06.002. ISSN 2468-0427. PMC 6002118. PMID 29928743.
Alizon S, Hurford A, Mideo N, Van Baalen M (February 2009). "Virulence evolution and the trade-off hypothesis: history, current state of affairs and the future". Journal of Evolutionary Biology. 22 (2): 245–59. doi:10.1111/j.1420-9101.2008.01658.x. PMID 19196383. S2CID 1586057.
S "International Studies". CONVERGE | Natural Hazards Center. Retrieved January 18, 2024.
Secretariat, Treasury Board of Canada (October 27, 2015). "Law Management". Canada. Retrieved January 18, 2024.
Kowarski, Ilana (June 21, 2021). "Library Science and How to Become a Librarian".
"Primary Functions of Management | Principles of Management". courses.lumenlearning.com. Retrieved January 18, 2024.
Albrecht, Maria Gomez; Green, Mark; Hoffman, Linda (January 25, 2023). Principles of Marketing. ISBN 978-1-951693-88-6.
"8.1: What is Political Economy?". Social Sci LibreTexts. February 22, 2022. Retrieved January 18, 2024.
Zaki Badawi, A (2002). Dictionary of the Social Sciences – Oxford Reference. doi:10.1093/acref/9780195123715.001.0001. ISBN 978-0-19-512371-5.
Josephson-Storm, Jason (2017). The Myth of Disenchantment: Magic, Modernity, and the Birth of the Human Sciences. Chicago: University of Chicago Press. pp. 101–14. ISBN 978-0-226-40336-6.
A.H. Halsey (2004), A history of sociology in Britain: science, literature, and society, p. 34
Geoffrey Duncan Mitchell (1970), A new dictionary of sociology, p. 201
Willcox, Walter (1938) The Founder of Statistics.
Eykhoff, Pieter System Identification: Parameter and State Estimation, Wiley & Sons, (1974). ISBN 978-0-471-24980-1
Administration for Children and Families (2010) The Program Manager's Guide to Evaluation. Chapter 2: What is program evaluation?.
Shackman, Gene (February 11, 2018), What Is Program Evaluation: A Beginner's Guide (Presentation Slides), The Global Social Change Research Project, SSRN 3060080
Bourdieu, Pierre (1992). "Double Bind et Conversion". Pour Une Anthropologie Réflexive. Paris: Le Seuil.
Giddens, Anthony (1987). Social Theory and Modern Sociology. Polity Press.
Alejandro, Audrey (2021). "Reflexive discourse analysis: A methodology for the practice of reflexivity". European Journal of International Relations. 27 (1): 171. doi:10.1177/1354066120969789. ISSN 1354-0661. S2CID 229461433.
Alejandro, Audrey (2021). "Reflexive discourse analysis: A methodology for the practice of reflexivity". European Journal of International Relations. 27 (1): 154. doi:10.1177/1354066120969789. ISSN 1354-0661. S2CID 229461433.
Peterson's (Firm : 2006– ). (2007). Peterson's graduate programs in the humanities, arts, & social sciences, 2007. Lawrenceville, New Jersey: Peterson's.
Overland, Indra; Sovacool, Benjamin K. (April 1, 2020). "The misallocation of climate research funding". Energy Research & Social Science. 62: 101349. doi:10.1016/j.erss.2019.101349. hdl:11250/2647605. ISSN 2214-6296.
Alejandro, Audrey (October 10, 2018). Western Dominance in International Relations?. Routledge. p. 60. doi:10.4324/9781315170480. ISBN 978-1-315-17048-0. S2CID 158923831.
Trindade, Hélgio (June 2005). "Social sciences in Brazil in perspective: foundation, consolidation and diversification". Social Science Information. 44 (2–3): 283–357. doi:10.1177/0539018405053291. ISSN 0539-0184. S2CID 145514260.
Jatobá, Daniel (2013). "Los Desarrollos Académicos de Las Relaciones Internacionales EnBrasil: Elementos Sociológicos, Institucionales Y Epistemológicos". Relaciones Internacionales. 22 (22): 27–47. doi:10.15366/relacionesinternacionales2013.22.002. hdl:10486/677456.
Bibliography
Michie, Jonathan, ed. Reader's Guide to the Social Sciences (2 vol. 2001) 1970 pages annotating the major topics in the late 20th century in all the social sciences.
20th and 21st centuries sources
Neil J. Smelser and Paul B. Baltes (2001). International Encyclopedia of the Social & Behavioral Sciences, Amsterdam: Elsevier.
Byrne, D.S. (1998). Complexity theory and the social sciences: an introduction. Routledge. ISBN 978-0-415-16296-8
Kuper, A., and Kuper, J. (1985). The Social Science Encyclopedia. London: Routledge & Kegan Paul. (ed., a limited preview of the 1996 version is available)
Lave, C.A., and March, J.G. (1993). An introduction to models in the social sciences. Lanham, Md: University Press of America.
Perry, John and Erna Perry. Contemporary Society: An Introduction to Social Science (12th Edition, 2008), college textbook
Potter, D. (1988). Society and the social sciences: An introduction. London: Routledge [u.a.].
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Sociology is the scientific and systematic study of human society that focuses on society, human social behavior, patterns of social relationships, social interaction, and aspects of culture associated with everyday life.[1][2][3] Regarded as a part of both the social sciences and humanities, sociology uses various methods of empirical investigation and critical analysis[4]: 3–5 to develop a body of knowledge about social order and social change.[4]: 32–40 Sociological subject matter ranges from micro-level analyses of individual interaction and agency to macro-level analyses of social systems and social structure. Applied sociological research may be applied directly to social policy and welfare, whereas theoretical approaches may focus on the understanding of social processes and phenomenological method.[5]
Traditional focuses of sociology include social stratification, social class, social mobility, religion, secularization, law, sexuality, gender, and deviance. Recent studies have added socio-technical aspects of the digital divide as a new focus.[6] As all spheres of human activity are affected by the interplay between social structure and individual agency, sociology has gradually expanded its focus to other subjects and institutions, such as health and the institution of medicine; economy; military; punishment and systems of control; the Internet; sociology of education; social capital; and the role of social activity in the development of scientific knowledge.
The range of social scientific methods has also expanded, as social researchers draw upon a variety of qualitative and quantitative techniques. The linguistic and cultural turns of the mid-20th century, especially, have led to increasingly interpretative, hermeneutic, and philosophical approaches towards the analysis of society. Conversely, the turn of the 21st century has seen the rise of new analytically, mathematically, and computationally rigorous techniques, such as agent-based modelling and social network analysis.[7][8]
Social research has influence throughout various industries and sectors of life, such as among politicians, policy makers, and legislators; educators; planners; administrators; developers; business magnates and managers; social workers; non-governmental organizations; and non-profit organizations, as well as individuals interested in resolving social issues in general.
History
Main article: History of sociology
Further information: List of sociologists and Timeline of sociology
Ibn Khaldun statue in Tunis, Tunisia (1332–1406)
Sociological reasoning predates the foundation of the discipline itself. Social analysis has origins in the common stock of universal, global knowledge and philosophy, having been carried out from as far back as the time of old comic poetry which features social and political criticism,[9] and ancient Greek philosophers Socrates, Plato, and Aristotle. For instance, the origin of the survey can be traced back to at least the Domesday Book in 1086,[10][11] while ancient philosophers such as Confucius wrote about the importance of social roles.[citation needed]
Medieval Arabic writings encompass a rich tradition that unveils early insights into the field of sociology. Some sources consider Ibn Khaldun, a 14th-century Muslim scholar from Tunisia,[note 1] to have been the father of sociology, although there is no reference to his work in the writings of European contributors to modern sociology.[12][13][14][15] Khaldun's Muqaddimah was considered to be amongst the first work to advance social-scientific reasoning on social cohesion and social conflict.[16][17][18][19][20][21]
Etymology
The word sociology derives part of its name from the Latin word socius ('companion' or 'fellowship'[22]). The suffix -logy ('the study of') comes from that of the Greek -λογία, derived from λόγος (lógos, 'word' or 'knowledge').[citation needed]
The term sociology was first coined in 1780 by the French essayist Emmanuel-Joseph Sieyès in an unpublished manuscript.[23][note 2] Sociology was later defined independently by French philosopher of science Auguste Comte (1798–1857) in 1838[24] as a new way of looking at society.[25]: 10 Comte had earlier used the term social physics, but it had been subsequently appropriated by others, most notably the Belgian statistician Adolphe Quetelet. Comte endeavored to unify history, psychology, and economics through the scientific understanding of social life. Writing shortly after the malaise of the French Revolution, he proposed that social ills could be remedied through sociological positivism, an epistemological approach outlined in the Course in Positive Philosophy (1830–1842), later included in A General View of Positivism (1848). Comte believed a positivist stage would mark the final era in the progression of human understanding, after conjectural theological and metaphysical phases.[26] In observing the circular dependence of theory and observation in science, and having classified the sciences, Comte may be regarded as the first philosopher of science in the modern sense of the term.[27][28]
Auguste Comte (1798–1857)
Comte gave a powerful impetus to the development of sociology, an impetus that bore fruit in the later decades of the nineteenth century. To say this is certainly not to claim that French sociologists such as Durkheim were devoted disciples of the high priest of positivism. But by insisting on the irreducibility of each of his basic sciences to the particular science of sciences which it presupposed in the hierarchy and by emphasizing the nature of sociology as the scientific study of social phenomena Comte put sociology on the map. To be sure, [its] beginnings can be traced back well beyond Montesquieu, for example, and to Condorcet, not to speak of Saint-Simon, Comte's immediate predecessor. But Comte's clear recognition of sociology as a particular science, with a character of its own, justified Durkheim in regarding him as the father or founder of this science, even though Durkheim did not accept the idea of the three states and criticized Comte's approach to sociology.
— Frederick Copleston, A History of Philosophy: IX Modern Philosophy (1974), p. 118
Karl Marx (1818–1883)
Marx
Both Comte and Karl Marx set out to develop scientifically justified systems in the wake of European industrialization and secularization, informed by various key movements in the philosophies of history and science. Marx rejected Comtean positivism[29] but in attempting to develop a "science of society" nevertheless came to be recognized as a founder of sociology as the word gained wider meaning. For Isaiah Berlin, even though Marx did not consider himself to be a sociologist, he may be regarded as the "true father" of modern sociology, "in so far as anyone can claim the title."[30]: 130
To have given clear and unified answers in familiar empirical terms to those theoretical questions which most occupied men's minds at the time, and to have deduced from them clear practical directives without creating obviously artificial links between the two, was the principal achievement of Marx's theory. The sociological treatment of historical and moral problems, which Comte and after him, Spencer and Taine, had discussed and mapped, became a precise and concrete study only when the attack of militant Marxism made its conclusions a burning issue, and so made the search for evidence more zealous and the attention to method more intense.[30]: 13–14
Spencer
Herbert Spencer (1820–1903)
Herbert Spencer was one of the most popular and influential 19th-century sociologists. It is estimated that he sold one million books in his lifetime, far more than any other sociologist at the time.[31] So strong was his influence that many other 19th-century thinkers, including Émile Durkheim, defined their ideas in relation to his. Durkheim's Division of Labour in Society is to a large extent an extended debate with Spencer from whose sociology Durkheim borrowed extensively.[32]
Also a notable biologist, Spencer coined the term survival of the fittest. While Marxian ideas defined one strand of sociology, Spencer was a critic of socialism, as well as a strong advocate for a laissez-faire style of government. His ideas were closely observed by conservative political circles, especially in the United States and England.[33]
Foundations of the academic discipline
Main articles: Émile Durkheim and Social facts
Émile Durkheim
The first formal Department of Sociology in the world was established in 1892 by Albion Small—from the invitation of William Rainey Harper—at the University of Chicago. The American Journal of Sociology was founded shortly thereafter in 1895 by Small as well.[34]
The institutionalization of sociology as an academic discipline, however, was chiefly led by Émile Durkheim, who developed positivism as a foundation for practical social research. While Durkheim rejected much of the detail of Comte's philosophy, he retained and refined its method, maintaining that the social sciences are a logical continuation of the natural ones into the realm of human activity, and insisting that they may retain the same objectivity, rationalism, and approach to causality.[35] Durkheim set up the first European department of sociology at the University of Bordeaux in 1895, publishing his Rules of the Sociological Method (1895).[36] For Durkheim, sociology could be described as the "science of institutions, their genesis and their functioning."[37]
Durkheim's monograph Suicide (1897) is considered a seminal work in statistical analysis by contemporary sociologists. Suicide is a case study of variations in suicide rates among Catholic and Protestant populations, and served to distinguish sociological analysis from psychology or philosophy. It also marked a major contribution to the theoretical concept of structural functionalism. By carefully examining suicide statistics in different police districts, he attempted to demonstrate that Catholic communities have a lower suicide rate than that of Protestants, something he attributed to social (as opposed to individual or psychological) causes. He developed the notion of objective social facts to delineate a unique empirical object for the science of sociology to study.[35] Through such studies he posited that sociology would be able to determine whether any given society is healthy or pathological, and seek social reform to negate organic breakdown, or "social anomie".
Sociology quickly evolved as an academic response to the perceived challenges of modernity, such as industrialization, urbanization, secularization, and the process of rationalization.[38] The field predominated in continental Europe, with British anthropology and statistics generally following on a separate trajectory. By the turn of the 20th century, however, many theorists were active in the English-speaking world. Few early sociologists were confined strictly to the subject, interacting also with economics, jurisprudence, psychology and philosophy, with theories being appropriated in a variety of different fields. Since its inception, sociological epistemology, methods, and frames of inquiry, have significantly expanded and diverged.[5]
Durkheim, Marx, and the German theorist Max Weber are typically cited as the three principal architects of sociology.[39] Herbert Spencer, William Graham Sumner, Lester F. Ward, W.E.B. Du Bois, Vilfredo Pareto, Alexis de Tocqueville, Werner Sombart, Thorstein Veblen, Ferdinand Tönnies, Georg Simmel, Jane Addams and Karl Mannheim are often included on academic curricula as founding theorists. Curricula also may include Charlotte Perkins Gilman, Marianne Weber, Harriet Martineau, and Friedrich Engels as founders of the feminist tradition in sociology. Each key figure is associated with a particular theoretical perspective and orientation.[40]
Marx and Engels associated the emergence of modern society above all with the development of capitalism; for Durkheim it was connected in particular with industrialization and the new social division of labor which this brought about; for Weber it had to do with the emergence of a distinctive way of thinking, the rational calculation which he associated with the Protestant Ethic (more or less what Marx and Engels speak of in terms of those 'icy waves of egotistical calculation'). Together the works of these great classical sociologists suggest what Giddens has recently described as 'a multidimensional view of institutions of modernity' and which emphasises not only capitalism and industrialism as key institutions of modernity, but also 'surveillance' (meaning 'control of information and social supervision') and 'military power' (control of the means of violence in the context of the industrialisation of war).[40]
— John Harriss, The Second Great Transformation? Capitalism at the End of the Twentieth Century (1992)
Further developments
Bust of Ferdinand Tönnies in Husum, Germany
The first college course entitled "Sociology" was taught in the United States at Yale in 1875 by William Graham Sumner.[41] In 1883, Lester F. Ward, who later became the first president of the American Sociological Association (ASA), published Dynamic Sociology—Or Applied social science as based upon statical sociology and the less complex sciences, attacking the laissez-faire sociology of Herbert Spencer and Sumner.[33] Ward's 1,200-page book was used as core material in many early American sociology courses. In 1890, the oldest continuing American course in the modern tradition began at the University of Kansas, lectured by Frank W. Blackmar.[42] The Department of Sociology at the University of Chicago was established in 1892 by Albion Small, who also published the first sociology textbook: An introduction to the study of society.[43] George Herbert Mead and Charles Cooley, who had met at the University of Michigan in 1891 (along with John Dewey), moved to Chicago in 1894.[44] Their influence gave rise to social psychology and the symbolic interactionism of the modern Chicago School.[45] The American Journal of Sociology was founded in 1895, followed by the ASA in 1905.[43]
The sociological canon of classics with Durkheim and Max Weber at the top owes its existence in part to Talcott Parsons, who is largely credited with introducing both to American audiences.[46] Parsons consolidated the sociological tradition and set the agenda for American sociology at the point of its fastest disciplinary growth. Sociology in the United States was less historically influenced by Marxism than its European counterpart, and to this day broadly remains more statistical in its approach.[47]
The first sociology department established in the United Kingdom was at the London School of Economics and Political Science (home of the British Journal of Sociology) in 1904.[48] Leonard Trelawny Hobhouse and Edvard Westermarck became the lecturers in the discipline at the University of London in 1907.[49][50] Harriet Martineau, an English translator of Comte, has been cited as the first female sociologist.[51] In 1909, the German Sociological Association was founded by Ferdinand Tönnies and Max Weber, among others. Weber established the first department in Germany at the Ludwig Maximilian University of Munich in 1919, having presented an influential new antipositivist sociology.[52] In 1920, Florian Znaniecki set up the first department in Poland. The Institute for Social Research at the University of Frankfurt (later to become the Frankfurt School of critical theory) was founded in 1923.[53] International co-operation in sociology began in 1893, when René Worms founded the Institut International de Sociologie, an institution later eclipsed by the much larger International Sociological Association (ISA), founded in 1949.[54]
Theoretical traditions
Main article: Sociological theory
Three stages of Sociology
Positivism and anti-positivism
Positivism
Main article: Positivism
The overarching methodological principle of positivism is to conduct sociology in broadly the same manner as natural science. An emphasis on empiricism and the scientific method is sought to provide a tested foundation for sociological research based on the assumption that the only authentic knowledge is scientific knowledge, and that such knowledge can only arrive by positive affirmation through scientific methodology.[citation needed]
Our main goal is to extend scientific rationalism to human conduct.... What has been called our positivism is but a consequence of this rationalism.[55]
— Émile Durkheim, The Rules of Sociological Method (1895)
The term has long since ceased to carry this meaning; there are no fewer than twelve distinct epistemologies that are referred to as positivism.[35][56] Many of these approaches do not self-identify as "positivist", some because they themselves arose in opposition to older forms of positivism, and some because the label has over time become a pejorative term[35] by being mistakenly linked with a theoretical empiricism. The extent of antipositivist criticism has also diverged, with many rejecting the scientific method and others only seeking to amend it to reflect 20th-century developments in the philosophy of science. However, positivism (broadly understood as a scientific approach to the study of society) remains dominant in contemporary sociology, especially in the United States.[35]
Loïc Wacquant distinguishes three major strains of positivism: Durkheimian, Logical, and Instrumental.[35] None of these are the same as that set forth by Comte, who was unique in advocating such a rigid (and perhaps optimistic) version.[57][4]: 94–8, 100–4 While Émile Durkheim rejected much of the detail of Comte's philosophy, he retained and refined its method. Durkheim maintained that the social sciences are a logical continuation of the natural ones into the realm of human activity, and insisted that they should retain the same objectivity, rationalism, and approach to causality.[35] He developed the notion of objective sui generis "social facts" to serve as unique empirical objects for the science of sociology to study.[35]
The variety of positivism that remains dominant today is termed instrumental positivism. This approach eschews epistemological and metaphysical concerns (such as the nature of social facts) in favour of methodological clarity, replicability, reliability and validity.[58] This positivism is more or less synonymous with quantitative research, and so only resembles older positivism in practice. Since it carries no explicit philosophical commitment, its practitioners may not belong to any particular school of thought. Modern sociology of this type is often credited to Paul Lazarsfeld,[35] who pioneered large-scale survey studies and developed statistical techniques for analysing them. This approach lends itself to what Robert K. Merton called middle-range theory: abstract statements that generalize from segregated hypotheses and empirical regularities rather than starting with an abstract idea of a social whole.[59]
Anti-positivism
Main article: Anti-positivism
The German philosopher Hegel criticised traditional empiricist epistemology, which he rejected as uncritical, and determinism, which he viewed as overly mechanistic.[4]: 169 Karl Marx's methodology borrowed from Hegelian dialecticism but also a rejection of positivism in favour of critical analysis, seeking to supplement the empirical acquisition of "facts" with the elimination of illusions.[4]: 202–3 He maintained that appearances need to be critiqued rather than simply documented. Early hermeneuticians such as Wilhelm Dilthey pioneered the distinction between natural and social science ('Geisteswissenschaft'). Various neo-Kantian philosophers, phenomenologists and human scientists further theorized how the analysis of the social world differs to that of the natural world due to the irreducibly complex aspects of human society, culture, and being.[60][61]
In the Italian context of development of social sciences and of sociology in particular, there are oppositions to the first foundation of the discipline, sustained by speculative philosophy in accordance with the antiscientific tendencies matured by critique of positivism and evolutionism, so a tradition Progressist struggles to establish itself.[62]
At the turn of the 20th century, the first generation of German sociologists formally introduced methodological anti-positivism, proposing that research should concentrate on human cultural norms, values, symbols, and social processes viewed from a resolutely subjective perspective. Max Weber argued that sociology may be loosely described as a science as it is able to identify causal relationships of human "social action"—especially among "ideal types", or hypothetical simplifications of complex social phenomena.[4]: 239–40 As a non-positivist, however, Weber sought relationships that are not as "historical, invariant, or generalisable"[4]: 241 as those pursued by natural scientists. Fellow German sociologist, Ferdinand Tönnies, theorised on two crucial abstract concepts with his work on "gemeinschaft and gesellschaft" (lit. 'community' and 'society'). Tönnies marked a sharp line between the realm of concepts and the reality of social action: the first must be treated axiomatically and in a deductive way ("pure sociology"), whereas the second empirically and inductively ("applied sociology").[63]
Max Weber
[Sociology is] ... the science whose object is to interpret the meaning of social action and thereby give a causal explanation of the way in which the action proceeds and the effects which it produces. By 'action' in this definition is meant the human behaviour when and to the extent that the agent or agents see it as subjectively meaningful ... the meaning to which we refer may be either (a) the meaning actually intended either by an individual agent on a particular historical occasion or by a number of agents on an approximate average in a given set of cases, or (b) the meaning attributed to the agent or agents, as types, in a pure type constructed in the abstract. In neither case is the 'meaning' to be thought of as somehow objectively 'correct' or 'true' by some metaphysical criterion. This is the difference between the empirical sciences of action, such as sociology and history, and any kind of prior discipline, such as jurisprudence, logic, ethics, or aesthetics whose aim is to extract from their subject-matter 'correct' or 'valid' meaning.[64]
— Max Weber, The Nature of Social Action (1922), p. 7
Both Weber and Georg Simmel pioneered the "Verstehen" (or 'interpretative') method in social science; a systematic process by which an outside observer attempts to relate to a particular cultural group, or indigenous people, on their own terms and from their own point of view.[65] Through the work of Simmel, in particular, sociology acquired a possible character beyond positivist data-collection or grand, deterministic systems of structural law. Relatively isolated from the sociological academy throughout his lifetime, Simmel presented idiosyncratic analyses of modernity more reminiscent of the phenomenological and existential writers than of Comte or Durkheim, paying particular concern to the forms of, and possibilities for, social individuality.[66] His sociology engaged in a neo-Kantian inquiry into the limits of perception, asking 'What is society?' in a direct allusion to Kant's question 'What is nature?'[67]
Georg Simmel
The deepest problems of modern life flow from the attempt of the individual to maintain the independence and individuality of his existence against the sovereign powers of society, against the weight of the historical heritage and the external culture and technique of life. The antagonism represents the most modern form of the conflict which primitive man must carry on with nature for his bodily existence. The eighteenth century may have called for liberation from all the ties which grew up historically in politics, in religion, in morality, and in economics to permit the original natural virtue of man, which is equal in everyone, to develop without inhibition; the nineteenth century may have sought to promote, in addition to man's freedom, his individuality (which is connected with the division of labor) and his achievements which make him unique and indispensable but which at the same time make him so much the more dependent on the complementary activity of others; Nietzsche may have seen the relentless struggle of the individual as the prerequisite for his full development, while socialism found the same thing in the suppression of all competition – but in each of these the same fundamental motive was at work, namely the resistance of the individual to being leveled, swallowed up in the social-technological mechanism.[68]
— Georg Simmel, The Metropolis and Mental Life (1903)
Classical theory
The contemporary discipline of sociology is theoretically multi-paradigmatic[69] in line with the contentions of classical social theory. Randall Collins' well-cited survey of sociological theory[70] retroactively labels various theorists as belonging to four theoretical traditions: Functionalism, Conflict, Symbolic Interactionism, and Utilitarianism.[71]
Accordingly, modern sociological theory predominantly descends from functionalist (Durkheim) and conflict (Marx and Weber) approaches to social structure, as well as from symbolic-interactionist approaches to social interaction, such as micro-level structural (Simmel) and pragmatist (Mead, Cooley) perspectives. Utilitarianism (also known as rational choice or social exchange), although often associated with economics, is an established tradition within sociological theory.[72][73]
Lastly, as argued by Raewyn Connell, a tradition that is often forgotten is that of Social Darwinism, which applies the logic of Darwinian biological evolution to people and societies.[74] This tradition often aligns with classical functionalism, and was once the dominant theoretical stance in American sociology, from c. 1881 – c. 1915,[75] associated with several founders of sociology, primarily Herbert Spencer, Lester F. Ward, and William Graham Sumner.
Contemporary sociological theory retains traces of each of these traditions and they are by no means mutually exclusive.[citation needed]
Functionalism
Main article: Structural functionalism
A broad historical paradigm in both sociology and anthropology, functionalism addresses the social structure—referred to as "social organization" by the classical theorists—with respect to the whole as well as the necessary function of the whole's constituent elements. A common analogy (popularized by Herbert Spencer) is to regard norms and institutions as 'organs' that work towards the proper functioning of the entire 'body' of society.[76] The perspective was implicit in the original sociological positivism of Comte but was theorized in full by Durkheim, again with respect to observable, structural laws.
Functionalism also has an anthropological basis in the work of theorists such as Marcel Mauss, Bronisław Malinowski, and Radcliffe-Brown. It is in the latter's specific usage that the prefix "structural" emerged.[77] Classical functionalist theory is generally united by its tendency towards biological analogy and notions of social evolutionism, in that the basic form of society would increase in complexity and those forms of social organization that promoted solidarity would eventually overcome social disorganization. As Giddens states:[78]
Functionalist thought, from Comte onwards, has looked particularly towards biology as the science providing the closest and most compatible model for social science. Biology has been taken to provide a guide to conceptualizing the structure and the function of social systems and to analyzing processes of evolution via mechanisms of adaptation. Functionalism strongly emphasizes the pre-eminence of the social world over its individual parts (i.e. its constituent actors, human subjects).
Conflict theory
Main article: Conflict theory
Functionalist theories emphasize "cohesive systems" and are often contrasted with "conflict theories", which critique the overarching socio-political system or emphasize the inequality between particular groups. The following quotes from Durkheim[79] and Marx[80] epitomize the political, as well as theoretical, disparities, between functionalist and conflict thought respectively:
To aim for a civilization beyond that made possible by the nexus of the surrounding environment will result in unloosing sickness into the very society we live in. Collective activity cannot be encouraged beyond the point set by the condition of the social organism without undermining health.
— Émile Durkheim, The Division of Labour in Society (1893)
The history of all hitherto existing society is the history of class struggles. Freeman and slave, patrician and plebeian, lord and serf, guild-master and journeyman, in a word, oppressor and oppressed, stood in constant opposition to one another, carried on an uninterrupted, now hidden, now open fight, a fight that each time ended, either in a revolutionary re-constitution of society at large, or in the common ruin of the contending classes.
— Karl Marx & Friedrich Engels, The Communist Manifesto (1848)
Symbolic interactionism
Main articles: Symbolic interactionism, Dramaturgy (sociology), Interpretive sociology, and Phenomenological sociology
Symbolic interaction—often associated with interactionism, phenomenology, dramaturgy, interpretivism—is a sociological approach that places emphasis on subjective meanings and the empirical unfolding of social processes, generally accessed through micro-analysis.[81] This tradition emerged in the Chicago School of the 1920s and 1930s, which, prior to World War II, "had been the center of sociological research and graduate study."[82][page needed] The approach focuses on creating a framework for building a theory that sees society as the product of the everyday interactions of individuals. Society is nothing more than the shared reality that people construct as they interact with one another. This approach sees people interacting in countless settings using symbolic communications to accomplish the tasks at hand. Therefore, society is a complex, ever-changing mosaic of subjective meanings.[25]: 19 Some critics of this approach argue that it only looks at what is happening in a particular social situation, and disregards the effects that culture, race or gender (i.e. social-historical structures) may have in that situation.[25] Some important sociologists associated with this approach include Max Weber, George Herbert Mead, Erving Goffman, George Homans, and Peter Blau. It is also in this tradition that the radical-empirical approach of ethnomethodology emerges from the work of Harold Garfinkel.
Utilitarianism
Main articles: Utilitarianism, Rational choice theory, and Exchange theory
Utilitarianism is often referred to as exchange theory or rational choice theory in the context of sociology. This tradition tends to privilege the agency of individual rational actors and assumes that within interactions individuals always seek to maximize their own self-interest. As argued by Josh Whitford, rational actors are assumed to have four basic elements:[83]
"a knowledge of alternatives;"
"a knowledge of, or beliefs about the consequences of the various alternatives;"
"an ordering of preferences over outcomes;" and
"a decision rule, to select among the possible alternatives"
Exchange theory is specifically attributed to the work of George C. Homans, Peter Blau and Richard Emerson.[84] Organizational sociologists James G. March and Herbert A. Simon noted that an individual's rationality is bounded by the context or organizational setting. The utilitarian perspective in sociology was, most notably, revitalized in the late 20th century by the work of former ASA president James Coleman.[citation needed]
20th-century social theory
Following the decline of theories of sociocultural evolution in the United States, the interactionist thought of the Chicago School dominated American sociology. As Anselm Strauss describes, "we didn't think symbolic interaction was a perspective in sociology; we thought it was sociology."[82] Moreover, philosophical and psychological pragmatism grounded this tradition.[85] After World War II, mainstream sociology shifted to the survey-research of Paul Lazarsfeld at Columbia University and the general theorizing of Pitirim Sorokin, followed by Talcott Parsons at Harvard University. Ultimately, "the failure of the Chicago, Columbia, and Wisconsin [sociology] departments to produce a significant number of graduate students interested in and committed to general theory in the years 1936–45 was to the advantage of the Harvard department."[86] As Parsons began to dominate general theory, his work primarily referenced European sociology—almost entirely omitting citations of both the American tradition of sociocultural-evolution as well as pragmatism. In addition to Parsons' revision of the sociological canon (which included Marshall, Pareto, Weber and Durkheim), the lack of theoretical challenges from other departments nurtured the rise of the Parsonian structural-functionalist movement, which reached its crescendo in the 1950s, but by the 1960s was in rapid decline.[87]
By the 1980s, most functionalist perspectives in Europe had broadly been replaced by conflict-oriented approaches,[88] and to many in the discipline, functionalism was considered "as dead as a dodo:"[89] According to Giddens:[90]
The orthodox consensus terminated in the late 1960s and 1970s as the middle ground shared by otherwise competing perspectives gave way and was replaced by a baffling variety of competing perspectives. This third 'generation' of social theory includes phenomenologically inspired approaches, critical theory, ethnomethodology, symbolic interactionism, structuralism, post-structuralism, and theories written in the tradition of hermeneutics and ordinary language philosophy.
Pax Wisconsana
While some conflict approaches also gained popularity in the United States, the mainstream of the discipline instead shifted to a variety of empirically oriented middle-range theories with no single overarching, or "grand", theoretical orientation. John Levi Martin refers to this "golden age of methodological unity and theoretical calm" as the Pax Wisconsana,[91] as it reflected the composition of the sociology department at the University of Wisconsin–Madison: numerous scholars working on separate projects with little contention.[92] Omar Lizardo describes the pax wisconsana as "a Midwestern flavored, Mertonian resolution of the theory/method wars in which [sociologists] all agreed on at least two working hypotheses: (1) grand theory is a waste of time; [and] (2) good theory has to be good to think with or goes in the trash bin."[93] Despite the aversion to grand theory in the latter half of the 20th century, several new traditions have emerged that propose various syntheses: structuralism, post-structuralism, cultural sociology and systems theory.[citation needed] Some sociologists have called for a return to 'grand theory' to combat the rise of scientific and pragmatist influences within the tradition of sociological thought (see Duane Rousselle).[94]
Anthony Giddens
Structuralism
The structuralist movement originated primarily from the work of Durkheim as interpreted by two European scholars: Anthony Giddens, a sociologist, whose theory of structuration draws on the linguistic theory of Ferdinand de Saussure; and Claude Lévi-Strauss, an anthropologist. In this context, 'structure' does not refer to 'social structure', but to the semiotic understanding of human culture as a system of signs. One may delineate four central tenets of structuralism:[95]
Structure is what determines the structure of a whole.
Structuralists believe that every system has a structure.
Structuralists are interested in 'structural' laws that deal with coexistence rather than changes.
Structures are the 'real things' beneath the surface or the appearance of meaning.
The second tradition of structuralist thought, contemporaneous with Giddens, emerges from the American School of social network analysis in the 1970s and 1980s,[96] spearheaded by the Harvard Department of Social Relations led by Harrison White and his students. This tradition of structuralist thought argues that, rather than semiotics, social structure is networks of patterned social relations. And, rather than Levi-Strauss, this school of thought draws on the notions of structure as theorized by Levi-Strauss' contemporary anthropologist, Radcliffe-Brown.[97] Some[98] refer to this as "network structuralism", and equate it to "British structuralism" as opposed to the "French structuralism" of Levi-Strauss.
Post-structuralism
Post-structuralist thought has tended to reject 'humanist' assumptions in the construction of social theory.[99] Michel Foucault provides an important critique in his Archaeology of the Human Sciences, though Habermas (1986) and Rorty (1986) have both argued that Foucault merely replaces one such system of thought with another.[100][101] The dialogue between these intellectuals highlights a trend in recent years for certain schools of sociology and philosophy to intersect. The anti-humanist position has been associated with "postmodernism", a term used in specific contexts to describe an era or phenomena, but occasionally construed as a method.[citation needed]
Central theoretical problems
Overall, there is a strong consensus regarding the central problems of sociological theory, which are largely inherited from the classical theoretical traditions. This consensus is: how to link, transcend or cope with the following "big three" dichotomies:[102]
subjectivity and objectivity, which deal with knowledge;
structure and agency, which deal with action;
and synchrony and diachrony, which deal with time.
Lastly, sociological theory often grapples with the problem of integrating or transcending the divide between micro, meso, and macro-scale social phenomena, which is a subset of all three central problems.[citation needed]
Subjectivity and objectivity
Main articles: Objectivity (science), Objectivity (philosophy), and Subjectivity
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The problem of subjectivity and objectivity can be divided into two parts: a concern over the general possibilities of social actions, and the specific problem of social scientific knowledge. In the former, the subjective is often equated (though not necessarily) with the individual, and the individual's intentions and interpretations of the objective. The objective is often considered any public or external action or outcome, on up to society writ large. A primary question for social theorists, then, is how knowledge reproduces along the chain of subjective-objective-subjective, that is to say: how is intersubjectivity achieved? While, historically, qualitative methods have attempted to tease out subjective interpretations, quantitative survey methods also attempt to capture individual subjectivities. Qualitative methods take an approach to objective description known as in situ, meaning that descriptions must have appropriate contextual information to understand the information.[103]
The latter concern with scientific knowledge results from the fact that a sociologist is part of the very object they seek to explain, as Bourdieu explains:
How can the sociologist effect in practice this radical doubting which is indispensable for bracketing all the presuppositions inherent in the fact that she is a social being, that she is therefore socialised and led to feel "like a fish in water" within that social world whose structures she has internalised? How can she prevent the social world itself from carrying out the construction of the object, in a sense, through her, through these unself-conscious operations or operations unaware of themselves of which she is the apparent subject
— Pierre Bourdieu, "The Problem of Reflexive Sociology", An Invitation to Reflexive Sociology (1992), p. 235
Structure and agency
Main article: Structure and agency
Structure and agency, sometimes referred to as determinism versus voluntarism,[104] form an enduring ontological debate in social theory: "Do social structures determine an individual's behaviour or does human agency?" In this context, agency refers to the capacity of individuals to act independently and make free choices, whereas structure relates to factors that limit or affect the choices and actions of individuals (e.g. social class, religion, gender, ethnicity, etc.). Discussions over the primacy of either structure or agency relate to the core of sociological epistemology (i.e. "what is the social world made of?", "what is a cause in the social world, and what is an effect?").[105] A perennial question within this debate is that of "social reproduction": how are structures (specifically, structures producing inequality) reproduced through the choices of individuals?
Synchrony and diachrony
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Synchrony and diachrony (or statics and dynamics) within social theory are terms that refer to a distinction that emerged through the work of Levi-Strauss who inherited it from the linguistics of Ferdinand de Saussure.[97] Synchrony slices moments of time for analysis, thus it is an analysis of static social reality. Diachrony, on the other hand, attempts to analyse dynamic sequences. Following Saussure, synchrony would refer to social phenomena as a static concept like a language, while diachrony would refer to unfolding processes like actual speech. In Anthony Giddens' introduction to Central Problems in Social Theory, he states that, "in order to show the interdependence of action and structure…we must grasp the time space relations inherent in the constitution of all social interaction." And like structure and agency, time is integral to discussion of social reproduction.
In terms of sociology, historical sociology is often better positioned to analyse social life as diachronic, while survey research takes a snapshot of social life and is thus better equipped to understand social life as synchronized. Some argue that the synchrony of social structure is a methodological perspective rather than an ontological claim.[97] Nonetheless, the problem for theory is how to integrate the two manners of recording and thinking about social data.
Research methodology
Main article: Social research
Sociological research methods may be divided into two broad, though often supplementary, categories:[106]
Qualitative designs emphasize understanding of social phenomena through direct observation, communication with participants, or analysis of texts, and may stress contextual and subjective accuracy over generality.
Quantitative designs approach social phenomena through quantifiable evidence, and often rely on statistical analysis of many cases (or across intentionally designed treatments in an experiment) to establish valid and reliable general claims.
Sociologists are often divided into camps of support for particular research techniques. These disputes relate to the epistemological debates at the historical core of social theory. While very different in many aspects, both qualitative and quantitative approaches involve a systematic interaction between theory and data.[107] Quantitative methodologies hold the dominant position in sociology, especially in the United States.[35] In the discipline's two most cited journals, quantitative articles have historically outnumbered qualitative ones by a factor of two.[108] (Most articles published in the largest British journal, on the other hand, are qualitative.) Most textbooks on the methodology of social research are written from the quantitative perspective,[109] and the very term "methodology" is often used synonymously with "statistics". Practically all sociology PhD programmes in the United States require training in statistical methods. The work produced by quantitative researchers is also deemed more 'trustworthy' and 'unbiased' by the general public,[110] though this judgment continues to be challenged by antipositivists.[110]
The choice of method often depends largely on what the researcher intends to investigate. For example, a researcher concerned with drawing a statistical generalization across an entire population may administer a survey questionnaire to a representative sample population. By contrast, a researcher who seeks full contextual understanding of an individual's social actions may choose ethnographic participant observation or open-ended interviews. Studies will commonly combine, or 'triangulate', quantitative and qualitative methods as part of a 'multi-strategy' design. For instance, a quantitative study may be performed to obtain statistical patterns on a target sample, and then combined with a qualitative interview to determine the play of agency.[107]
Sampling
The bean machine, designed by early social research methodologist Sir Francis Galton to demonstrate the normal distribution, which is important to much quantitative hypothesis testing[a]
Quantitative methods are often used to ask questions about a population that is very large, making a census or a complete enumeration of all the members in that population infeasible. A 'sample' then forms a manageable subset of a population. In quantitative research, statistics are used to draw inferences from this sample regarding the population as a whole. The process of selecting a sample is referred to as 'sampling'. While it is usually best to sample randomly, concern with differences between specific subpopulations sometimes calls for stratified sampling. Conversely, the impossibility of random sampling sometimes necessitates nonprobability sampling, such as convenience sampling or snowball sampling.[107]
Methods
The following list of research methods is neither exclusive nor exhaustive:
Archival research (or the Historical method): Draws upon the secondary data located in historical archives and records, such as biographies, memoirs, journals, and so on.
Content analysis: The content of interviews and other texts is systematically analysed. Often data is 'coded' as a part of the 'grounded theory' approach using qualitative data analysis (QDA) software, such as Atlas.ti, MAXQDA, NVivo,[111] or QDA Miner.
Experimental research: The researcher isolates a single social process and reproduces it in a laboratory (for example, by creating a situation where unconscious sexist judgements are possible), seeking to determine whether or not certain social variables can cause, or depend upon, other variables (for instance, seeing if people's feelings about traditional gender roles can be manipulated by the activation of contrasting gender stereotypes).[112] Participants are randomly assigned to different groups that either serve as controls—acting as reference points because they are tested with regard to the dependent variable, albeit without having been exposed to any independent variables of interest—or receive one or more treatments. Randomization allows the researcher to be sure that any resulting differences between groups are the result of the treatment.
Longitudinal study: An extensive examination of a specific person or group over a long period of time.[citation needed]
Observation: Using data from the senses, the researcher records information about social phenomenon or behaviour. Observation techniques may or may not feature participation. In participant observation, the researcher goes into the field (e.g. a community or a place of work), and participates in the activities of the field for a prolonged period of time in order to acquire a deep understanding of it.[25]: 42 Data acquired through these techniques may be analysed either quantitatively or qualitatively. In the observation research, a sociologist might study global warming in some part of the world that is less populated.
Program Evaluation is a systematic method for collecting, analyzing, and using information to answer questions about projects, policies and programs,[113] particularly about their effectiveness and efficiency. In both the public and private sectors, stakeholders often want to know whether the programs they are funding, implementing, voting for, or objecting to are producing the intended effect. While program evaluation first focuses on this definition, important considerations often include how much the program costs per participant, how the program could be improved, whether the program is worthwhile, whether there are better alternatives, if there are unintended outcomes, and whether the program goals are appropriate and useful.[114]
Survey research: The researcher gathers data using interviews, questionnaires, or similar feedback from a set of people sampled from a particular population of interest. Survey items from an interview or questionnaire may be open-ended or closed-ended.[25]: 40 Data from surveys is usually analysed statistically on a computer.
Computational sociology
A social network diagram: individuals (or 'nodes') connected by relationships
Main article: Computational sociology
Sociologists increasingly draw upon computationally intensive methods to analyse and model social phenomena.[115] Using computer simulations, artificial intelligence, text mining, complex statistical methods, and new analytic approaches like social network analysis and social sequence analysis, computational sociology develops and tests theories of complex social processes through bottom-up modelling of social interactions.[7]
Although the subject matter and methodologies in social science differ from those in natural science or computer science, several of the approaches used in contemporary social simulation originated from fields such as physics and artificial intelligence.[116][117] By the same token, some of the approaches that originated in computational sociology have been imported into the natural sciences, such as measures of network centrality from the fields of social network analysis and network science. In relevant literature, computational sociology is often related to the study of social complexity.[118] Social complexity concepts such as complex systems, non-linear interconnection among macro and micro process, and emergence, have entered the vocabulary of computational sociology.[119] A practical and well-known example is the construction of a computational model in the form of an "artificial society", by which researchers can analyse the structure of a social system.[120][121]
Subfields
For a topical guide, see Outline of sociology.
Culture
Max Horkheimer (left, front), Theodor Adorno (right, front), and Jürgen Habermas (right, back), 1965
Main articles: Sociology of culture, Cultural criminology, and Cultural studies
Sociologists' approach to culture can be divided into "sociology of culture" and "cultural sociology"—terms which are similar, though not entirely interchangeable. Sociology of culture is an older term, and considers some topics and objects as more or less "cultural" than others. Conversely, cultural sociology sees all social phenomena as inherently cultural.[122] Sociology of culture often attempts to explain certain cultural phenomena as a product of social processes, while cultural sociology sees culture as a potential explanation of social phenomena.[123]
For Simmel, culture referred to "the cultivation of individuals through the agency of external forms which have been objectified in the course of history."[66] While early theorists such as Durkheim and Mauss were influential in cultural anthropology, sociologists of culture are generally distinguished by their concern for modern (rather than primitive or ancient) society. Cultural sociology often involves the hermeneutic analysis of words, artefacts and symbols, or ethnographic interviews. However, some sociologists employ historical-comparative or quantitative techniques in the analysis of culture, Weber and Bourdieu for instance. The subfield is sometimes allied with critical theory in the vein of Theodor W. Adorno, Walter Benjamin, and other members of the Frankfurt School. Loosely distinct from the sociology of culture is the field of cultural studies. Birmingham School theorists such as Richard Hoggart and Stuart Hall questioned the division between "producers" and "consumers" evident in earlier theory, emphasizing the reciprocity in the production of texts. Cultural Studies aims to examine its subject matter in terms of cultural practices and their relation to power. For example, a study of a subculture (e.g. white working class youth in London) would consider the social practices of the group as they relate to the dominant class. The "cultural turn" of the 1960s ultimately placed culture much higher on the sociological agenda.[citation needed]
Art, music and literature
Main articles: Sociology of literature, Sociology of art, Sociology of film, and Sociology of music
Sociology of literature, film, and art is a subset of the sociology of culture. This field studies the social production of artistic objects and its social implications. A notable example is Pierre Bourdieu's Les Règles de L'Art: Genèse et Structure du Champ Littéraire (1992).[124] None of the founding fathers of sociology produced a detailed study of art, but they did develop ideas that were subsequently applied to literature by others. Marx's theory of ideology was directed at literature by Pierre Macherey, Terry Eagleton and Fredric Jameson. Weber's theory of modernity as cultural rationalization, which he applied to music, was later applied to all the arts, literature included, by Frankfurt School writers such as Theodor Adorno and Jürgen Habermas. Durkheim's view of sociology as the study of externally defined social facts was redirected towards literature by Robert Escarpit. Bourdieu's own work is clearly indebted to Marx, Weber and Durkheim.[citation needed]
Criminality, deviance, law and punishment
Main articles: Criminology, Sociology of law, Sociology of punishment, Deviance, and Social disorganization theory
Criminologists analyse the nature, causes, and control of criminal activity, drawing upon methods across sociology, psychology, and the behavioural sciences. The sociology of deviance focuses on actions or behaviours that violate norms, including both infringements of formally enacted rules (e.g., crime) and informal violations of cultural norms. It is the remit of sociologists to study why these norms exist; how they change over time; and how they are enforced. The concept of social disorganization is when the broader social systems leads to violations of norms. For instance, Robert K. Merton produced a typology of deviance, which includes both individual and system level causal explanations of deviance.[125]
Sociology of law
The study of law played a significant role in the formation of classical sociology. Durkheim famously described law as the "visible symbol" of social solidarity.[126] The sociology of law refers to both a sub-discipline of sociology and an approach within the field of legal studies. Sociology of law is a diverse field of study that examines the interaction of law with other aspects of society, such as the development of legal institutions and the effect of laws on social change and vice versa. For example, an influential recent work in the field relies on statistical analyses to argue that the increase in incarceration in the US over the last 30 years is due to changes in law and policing and not to an increase in crime; and that this increase has significantly contributed to the persistence of racial stratification.[127]
Communications and information technologies
The sociology of communications and information technologies includes "the social aspects of computing, the Internet, new media, computer networks, and other communication and information technologies."[128]
Internet and digital media
Main article: Sociology of the Internet
The Internet is of interest to sociologists in various ways, most practically as a tool for research and as a discussion platform.[129] The sociology of the Internet in the broad sense concerns the analysis of online communities (e.g. newsgroups, social networking sites) and virtual worlds, meaning that there is often overlap with community sociology. Online communities may be studied statistically through network analysis or interpreted qualitatively through virtual ethnography. Moreover, organizational change is catalysed through new media, thereby influencing social change at-large, perhaps forming the framework for a transformation from an industrial to an informational society. One notable text is Manuel Castells' The Internet Galaxy—the title of which forms an inter-textual reference to Marshall McLuhan's The Gutenberg Galaxy.[130] Closely related to the sociology of the Internet is digital sociology, which expands the scope of study to address not only the internet but also the impact of the other digital media and devices that have emerged since the first decade of the twenty-first century.[citation needed]
Media
Main article: Media studies
As with cultural studies, media study is a distinct discipline that owes to the convergence of sociology and other social sciences and humanities, in particular, literary criticism and critical theory. Though neither the production process nor the critique of aesthetic forms is in the remit of sociologists, analyses of socializing factors, such as ideological effects and audience reception, stem from sociological theory and method. Thus the 'sociology of the media' is not a subdiscipline per se, but the media is a common and often indispensable topic.[citation needed]
Economic sociology
Main article: Economic sociology
The term "economic sociology" was first used by William Stanley Jevons in 1879, later to be coined in the works of Durkheim, Weber, and Simmel between 1890 and 1920.[131] Economic sociology arose as a new approach to the analysis of economic phenomena, emphasizing class relations and modernity as a philosophical concept. The relationship between capitalism and modernity is a salient issue, perhaps best demonstrated in Weber's The Protestant Ethic and the Spirit of Capitalism (1905) and Simmel's The Philosophy of Money (1900). The contemporary period of economic sociology, also known as new economic sociology, was consolidated by the 1985 work of Mark Granovetter titled "Economic Action and Social Structure: The Problem of Embeddedness". This work elaborated the concept of embeddedness, which states that economic relations between individuals or firms take place within existing social relations (and are thus structured by these relations as well as the greater social structures of which those relations are a part). Social network analysis has been the primary methodology for studying this phenomenon. Granovetter's theory of the strength of weak ties and Ronald Burt's concept of structural holes are two of the best known theoretical contributions of this field.[citation needed]
Work, employment, and industry
Main articles: sociology of work and Industrial relations
The sociology of work, or industrial sociology, examines "the direction and implications of trends in technological change, globalization, labour markets, work organization, managerial practices and employment relations to the extent to which these trends are intimately related to changing patterns of inequality in modern societies and to the changing experiences of individuals and families the ways in which workers challenge, resist and make their own contributions to the patterning of work and shaping of work institutions."[132]
Education
Main article: Sociology of education
The sociology of education is the study of how educational institutions determine social structures, experiences, and other outcomes. It is particularly concerned with the schooling systems of modern industrial societies.[133] A classic 1966 study in this field by James Coleman, known as the "Coleman Report", analysed the performance of over 150,000 students and found that student background and socioeconomic status are much more important in determining educational outcomes than are measured differences in school resources (i.e. per pupil spending).[134] The controversy over "school effects" ignited by that study has continued to this day. The study also found that socially disadvantaged black students profited from schooling in racially mixed classrooms, and thus served as a catalyst for desegregation busing in American public schools.[citation needed]
Environment
Main articles: Environmental sociology and Sociology of disaster
Environmental sociology is the study of human interactions with the natural environment, typically emphasizing human dimensions of environmental problems, social impacts of those problems, and efforts to resolve them. As with other sub-fields of sociology, scholarship in environmental sociology may be at one or multiple levels of analysis, from global (e.g. world-systems) to local, societal to individual. Attention is paid also to the processes by which environmental problems become defined and known to humans. As argued by notable environmental sociologist John Bellamy Foster, the predecessor to modern environmental sociology is Marx's analysis of the metabolic rift, which influenced contemporary thought on sustainability. Environmental sociology is often interdisciplinary and overlaps with the sociology of risk, rural sociology and the sociology of disaster.[citation needed]
Human ecology
Main articles: Human ecology, Architectural sociology, Visual sociology, Sociology of space, and Urban sociology
Human ecology deals with interdisciplinary study of the relationship between humans and their natural, social, and built environments. In addition to Environmental sociology, this field overlaps with architectural sociology, urban sociology, and to some extent visual sociology. In turn, visual sociology—which is concerned with all visual dimensions of social life—overlaps with media studies in that it uses photography, film and other technologies of media.[citation needed]
Social pre-wiring
Social pre-wiring deals with the study of fetal social behavior and social interactions in a multi-fetal environment. Specifically, social pre-wiring refers to the ontogeny of social interaction. Also informally referred to as, "wired to be social". The theory questions whether there is a propensity to socially oriented action already present before birth. Research in the theory concludes that newborns are born into the world with a unique genetic wiring to be social.[135]
Circumstantial evidence supporting the social pre-wiring hypothesis can be revealed when examining newborns' behavior. Newborns, not even hours after birth, have been found to display a preparedness for social interaction. This preparedness is expressed in ways such as their imitation of facial gestures. This observed behavior cannot be attributed to any current form of socialization or social construction. Rather, newborns most likely inherit to some extent social behavior and identity through genetics.[135]
Principal evidence of this theory is uncovered by examining Twin pregnancies. The main argument is, if there are social behaviors that are inherited and developed before birth, then one should expect twin foetuses to engage in some form of social interaction before they are born. Thus, ten foetuses were analyzed over a period of time using ultrasound techniques. Using kinematic analysis, the results of the experiment were that the twin foetuses would interact with each other for longer periods and more often as the pregnancies went on. Researchers were able to conclude that the performance of movements between the co-twins were not accidental but specifically aimed.[135]
The social pre-wiring hypothesis was proved correct:[135]
The central advance of this study is the demonstration that 'social actions' are already performed in the second trimester of gestation. Starting from the 14th week of gestation twin foetuses plan and execute movements specifically aimed at the co-twin. These findings force us to predate the emergence of social behavior: when the context enables it, as in the case of twin foetuses, other-directed actions are not only possible but predominant over self-directed actions.
Family, gender, and sexuality
Main articles: Sociology of the family, Sociology of childhood, Sociology of gender, Feminist sociology, Feminist theory, and Queer theory
"Rosie the Riveter" was an iconic symbol of the American homefront and a departure from gender roles due to wartime necessity.
Family, gender and sexuality form a broad area of inquiry studied in many sub-fields of sociology. A family is a group of people who are related by kinship ties :- Relations of blood / marriage / civil partnership or adoption. The family unit is one of the most important social institutions found in some form in nearly all known societies. It is the basic unit of social organization and plays a key role in socializing children into the culture of their society. The sociology of the family examines the family, as an institution and unit of socialization, with special concern for the comparatively modern historical emergence of the nuclear family and its distinct gender roles. The notion of "childhood" is also significant. As one of the more basic institutions to which one may apply sociological perspectives, the sociology of the family is a common component on introductory academic curricula. Feminist sociology, on the other hand, is a normative sub-field that observes and critiques the cultural categories of gender and sexuality, particularly with respect to power and inequality. The primary concern of feminist theory is the patriarchy and the systematic oppression of women apparent in many societies, both at the level of small-scale interaction and in terms of the broader social structure. Feminist sociology also analyses how gender interlocks with race and class to produce and perpetuate social inequalities.[136] "How to account for the differences in definitions of femininity and masculinity and in sex role across different societies and historical periods" is also a concern.[137]
Health, illness, and the body
Main articles: Sociology of health and illness and Medical sociology
The sociology of health and illness focuses on the social effects of, and public attitudes toward, illnesses, diseases, mental health and disabilities. This sub-field also overlaps with gerontology and the study of the ageing process. Medical sociology, by contrast, focuses on the inner-workings of the medical profession, its organizations, its institutions and how these can shape knowledge and interactions. In Britain, sociology was introduced into the medical curriculum following the Goodenough Report (1944).[138][139]
The sociology of the body and embodiment[140] takes a broad perspective on the idea of "the body" and includes "a wide range of embodied dynamics including human and non-human bodies, morphology, human reproduction, anatomy, body fluids, biotechnology, genetics". This often intersects with health and illness, but also theories of bodies as political, social, cultural, economic and ideological productions.[141] The ISA maintains a Research Committee devoted to "the Body in the Social Sciences".[142]
Death, dying, bereavement
A subfield of the sociology of health and illness that overlaps with cultural sociology is the study of death, dying and bereavement,[143] sometimes referred to broadly as the sociology of death. This topic is exemplified by the work of Douglas Davies and Michael C. Kearl.[citation needed]
Knowledge and science
Main articles: Sociology of knowledge, Sociology of scientific knowledge, and Sociology of the history of science
The sociology of knowledge is the study of the relationship between human thought and the social context within which it arises, and of the effects prevailing ideas have on societies. The term first came into widespread use in the 1920s, when a number of German-speaking theorists, most notably Max Scheler, and Karl Mannheim, wrote extensively on it. With the dominance of functionalism through the middle years of the 20th century, the sociology of knowledge tended to remain on the periphery of mainstream sociological thought. It was largely reinvented and applied much more closely to everyday life in the 1960s, particularly by Peter L. Berger and Thomas Luckmann in The Social Construction of Reality (1966) and is still central for methods dealing with qualitative understanding of human society (compare socially constructed reality). The "archaeological" and "genealogical" studies of Michel Foucault are of considerable contemporary influence.
The sociology of science involves the study of science as a social activity, especially dealing "with the social conditions and effects of science, and with the social structures and processes of scientific activity."[144] Important theorists in the sociology of science include Robert K. Merton and Bruno Latour. These branches of sociology have contributed to the formation of science and technology studies. Both the ASA and the BSA have sections devoted to the subfield of Science, Knowledge and Technology.[145][146] The ISA maintains a Research Committee on Science and Technology.[147]
Leisure
Main articles: Sociology of leisure and Sociology of sport
Sociology of leisure is the study of how humans organize their free time. Leisure includes a broad array of activities, such as sport, tourism, and the playing of games. The sociology of leisure is closely tied to the sociology of work, as each explores a different side of the work–leisure relationship. More recent studies in the field move away from the work–leisure relationship and focus on the relation between leisure and culture. This area of sociology began with Thorstein Veblen's Theory of the Leisure Class.[148]
Peace, war, and conflict
Main articles: Peace and conflict studies, Military sociology, and Sociology of terrorism
This subfield of sociology studies, broadly, the dynamics of war, conflict resolution, peace movements, war refugees, conflict resolution and military institutions.[149] As a subset of this subfield, military sociology aims towards the systematic study of the military as a social group rather than as an organization. It is a highly specialized sub-field which examines issues related to service personnel as a distinct group with coerced collective action based on shared interests linked to survival in vocation and combat, with purposes and values that are more defined and narrower than within civil society. Military sociology also concerns civilian-military relations and interactions between other groups or governmental agencies. Topics include the dominant assumptions held by those in the military, changes in military members' willingness to fight, military unionization, military professionalism, the increased utilization of women, the military industrial-academic complex, the military's dependence on research, and the institutional and organizational structure of military.[150]
Political sociology
Main article: Political sociology
Jürgen Habermas
Historically, political sociology concerned the relations between political organization and society. A typical research question in this area might be: "Why do so few American citizens choose to vote?"[151] In this respect questions of political opinion formation brought about some of the pioneering uses of statistical survey research by Paul Lazarsfeld. A major subfield of political sociology developed in relation to such questions, which draws on comparative history to analyse socio-political trends. The field developed from the work of Max Weber and Moisey Ostrogorsky.[152]
Contemporary political sociology includes these areas of research, but it has been opened up to wider questions of power and politics.[153] Today political sociologists are as likely to be concerned with how identities are formed that contribute to structural domination by one group over another; the politics of who knows how and with what authority; and questions of how power is contested in social interactions in such a way as to bring about widespread cultural and social change. Such questions are more likely to be studied qualitatively. The study of social movements and their effects has been especially important in relation to these wider definitions of politics and power.[154]
Political sociology has also moved beyond methodological nationalism and analysed the role of non-governmental organizations, the diffusion of the nation-state throughout the Earth as a social construct, and the role of stateless entities in the modern world society. Contemporary political sociologists also study inter-state interactions and human rights.[citation needed]
Population and demography
Main articles: Demography, Human ecology, and Mobilities
Demographers or sociologists of population study the size, composition and change over time of a given population. Demographers study how these characteristics impact, or are impacted by, various social, economic or political systems. The study of population is also closely related to human ecology and environmental sociology, which studies a population's relationship with the surrounding environment and often overlaps with urban or rural sociology. Researchers in this field may study the movement of populations: transportation, migrations, diaspora, etc., which falls into the subfield known as mobilities studies and is closely related to human geography. Demographers may also study spread of disease within a given population or epidemiology.[citation needed]
Public sociology
Main article: Public sociology
Public sociology refers to an approach to the discipline which seeks to transcend the academy in order to engage with wider audiences. It is perhaps best understood as a style of sociology rather than a particular method, theory, or set of political values. This approach is primarily associated with Michael Burawoy who contrasted it with professional sociology, a form of academic sociology that is concerned primarily with addressing other professional sociologists. Public sociology is also part of the broader field of science communication or science journalism.[citation needed]
Race and ethnic relations
Main articles: Sociology of race and ethnic relations and Sociology of immigration
The sociology of race and of ethnic relations is the area of the discipline that studies the social, political, and economic relations between races and ethnicities at all levels of society. This area encompasses the study of racism, residential segregation, and other complex social processes between different racial and ethnic groups. This research frequently interacts with other areas of sociology such as stratification and social psychology, as well as with postcolonial theory. At the level of political policy, ethnic relations are discussed in terms of either assimilationism or multiculturalism. Anti-racism forms another style of policy, particularly popular in the 1960s and 1970s.[citation needed]
Religion
Main article: Sociology of religion
The sociology of religion concerns the practices, historical backgrounds, developments, universal themes and roles of religion in society.[155] There is particular emphasis on the recurring role of religion in all societies and throughout recorded history. The sociology of religion is distinguished from the philosophy of religion in that sociologists do not set out to assess the validity of religious truth-claims, instead assuming what Peter L. Berger has described as a position of "methodological atheism".[156] It may be said that the modern formal discipline of sociology began with the analysis of religion in Durkheim's 1897 study of suicide rates among Roman Catholic and Protestant populations. Max Weber published four major texts on religion in a context of economic sociology and social stratification: The Protestant Ethic and the Spirit of Capitalism (1905), The Religion of China: Confucianism and Taoism (1915), The Religion of India: The Sociology of Hinduism and Buddhism (1915), and Ancient Judaism (1920). Contemporary debates often centre on topics such as secularization, civil religion, the intersection of religion and economics and the role of religion in a context of globalization and multiculturalism.[157]
Social change and development
Main articles: Social change, Development studies, Community development, and International development
The sociology of change and development attempts to understand how societies develop and how they can be changed. This includes studying many different aspects of society, for example demographic trends,[158] political or technological trends,[159] or changes in culture. Within this field, sociologists often use macrosociological methods or historical-comparative methods. In contemporary studies of social change, there are overlaps with international development or community development. However, most of the founders of sociology had theories of social change based on their study of history. For instance, Marx contended that the material circumstances of society ultimately caused the ideal or cultural aspects of society, while Weber argued that it was in fact the cultural mores of Protestantism that ushered in a transformation of material circumstances. In contrast to both, Durkheim argued that societies moved from simple to complex through a process of sociocultural evolution. Sociologists in this field also study processes of globalization and imperialism. Most notably, Immanuel Wallerstein extends Marx's theoretical frame to include large spans of time and the entire globe in what is known as world systems theory. Development sociology is also heavily influenced by post-colonialism. In recent years, Raewyn Connell issued a critique of the bias in sociological research towards countries in the Global North. She argues that this bias blinds sociologists to the lived experiences of the Global South, specifically, so-called, "Northern Theory" lacks an adequate theory of imperialism and colonialism.[citation needed]
There are many organizations studying social change, including the Fernand Braudel Center for the Study of Economies, Historical Systems, and Civilizations, and the Global Social Change Research Project.[citation needed]
Social networks
Harrison White
Main articles: Social network, Social network analysis, Figurational Sociology, Relational sociology, and Sociomapping
A social network is a social structure composed of individuals (or organizations) called "nodes", which are tied (connected) by one or more specific types of interdependency, such as friendship, kinship, financial exchange, dislike, sexual relationships, or relationships of beliefs, knowledge or prestige. Social networks operate on many levels, from families up to the level of nations, and play a critical role in determining the way problems are solved, organizations are run, and the degree to which individuals succeed in achieving their goals. An underlying theoretical assumption of social network analysis is that groups are not necessarily the building blocks of society: the approach is open to studying less-bounded social systems, from non-local communities to networks of exchange. Drawing theoretically from relational sociology, social network analysis avoids treating individuals (persons, organizations, states) as discrete units of analysis, it focuses instead on how the structure of ties affects and constitutes individuals and their relationships. In contrast to analyses that assume that socialization into norms determines behaviour, network analysis looks to see the extent to which the structure and composition of ties affect norms. On the other hand, recent research by Omar Lizardo also demonstrates that network ties are shaped and created by previously existing cultural tastes.[160] Social network theory is usually defined in formal mathematics and may include integration of geographical data into sociomapping.[citation needed]
Social psychology
Main articles: Social psychology (sociology) and Psychoanalytic sociology
Sociological social psychology focuses on micro-scale social actions. This area may be described as adhering to "sociological miniaturism", examining whole societies through the study of individual thoughts and emotions as well as behaviour of small groups.[161] One special concern to psychological sociologists is how to explain a variety of demographic, social, and cultural facts in terms of human social interaction. Some of the major topics in this field are social inequality, group dynamics, prejudice, aggression, social perception, group behaviour, social change, non-verbal behaviour, socialization, conformity, leadership, and social identity. Social psychology may be taught with psychological emphasis.[162] In sociology, researchers in this field are the most prominent users of the experimental method (however, unlike their psychological counterparts, they also frequently employ other methodologies). Social psychology looks at social influences, as well as social perception and social interaction.[162]
Stratification, poverty and inequality
Main articles: Social stratification, Social inequality, Social mobility, and Social class
Social stratification is the hierarchical arrangement of individuals into social classes, castes, and divisions within a society.[25]: 225 Modern Western societies stratification traditionally relates to cultural and economic classes arranged in three main layers: upper class, middle class, and lower class, but each class may be further subdivided into smaller classes (e.g. occupational).[163] Social stratification is interpreted in radically different ways within sociology. Proponents of structural functionalism suggest that, since the stratification of classes and castes is evident in all societies, hierarchy must be beneficial in stabilizing their existence. Conflict theorists, by contrast, critique the inaccessibility of resources and lack of social mobility in stratified societies.[citation needed]
Karl Marx distinguished social classes by their connection to the means of production in the capitalist system: the bourgeoisie own the means, but this effectively includes the proletariat itself as the workers can only sell their own labour power (forming the material base of the cultural superstructure). Max Weber critiqued Marxist economic determinism, arguing that social stratification is not based purely on economic inequalities, but on other status and power differentials (e.g. patriarchy). According to Weber, stratification may occur among at least three complex variables:
Property (class): A person's economic position in a society, based on birth and individual achievement.[25]: 243 Weber differs from Marx in that he does not see this as the supreme factor in stratification. Weber noted how managers of corporations or industries control firms they do not own; Marx would have placed such a person in the proletariat.
Prestige (status): A person's prestige, or popularity in a society. This could be determined by the kind of job this person does or wealth.
Power (political party): A person's ability to get their way despite the resistance of others. For example, individuals in state jobs, such as an employee of the Federal Bureau of Investigation, or a member of the United States Congress, may hold little property or status but they still hold immense power.[164]
Pierre Bourdieu provides a modern example in the concepts of cultural and symbolic capital. Theorists such as Ralf Dahrendorf have noted the tendency towards an enlarged middle-class in modern Western societies, particularly in relation to the necessity of an educated work force in technological or service-based economies.[165] Perspectives concerning globalization, such as dependency theory, suggest this effect owes to the shift of workers to the developing countries.[166]
Urban and rural sociology
Main articles: Urban sociology and Rural sociology
Urban sociology involves the analysis of social life and human interaction in metropolitan areas. It is a discipline seeking to provide advice for planning and policy making. After the Industrial Revolution, works such as Georg Simmel's The Metropolis and Mental Life (1903) focused on urbanization and the effect it had on alienation and anonymity. In the 1920s and 1930s The Chicago School produced a major body of theory on the nature of the city, important to both urban sociology and criminology, utilizing symbolic interactionism as a method of field research. Contemporary research is commonly placed in a context of globalization, for instance, in Saskia Sassen's study of the "global city".[167] Rural sociology, by contrast, is the analysis of non-metropolitan areas. As agriculture and wilderness tend to be a more prominent social fact in rural regions, rural sociologists often overlap with environmental sociologists.[citation needed]
Community sociology
Often grouped with urban and rural sociology is that of community sociology or the sociology of community.[168] Taking various communities—including online communities—as the unit of analysis, community sociologists study the origin and effects of different associations of people. For instance, German sociologist Ferdinand Tönnies distinguished between two types of human association: gemeinschaft (usually translated as "community") and gesellschaft ("society" or "association"). In his 1887 work, Gemeinschaft und Gesellschaft, Tönnies argued that Gemeinschaft is perceived to be a tighter and more cohesive social entity, due to the presence of a "unity of will".[169] The 'development' or 'health' of a community is also a central concern of community sociologists also engage in development sociology, exemplified by the literature surrounding the concept of social capital.[citation needed]
Other academic disciplines
Sociology overlaps with a variety of disciplines that study society, in particular social anthropology, political science, economics, social work and social philosophy. Many comparatively new fields such as communication studies, cultural studies, demography and literary theory, draw upon methods that originated in sociology. The terms "social science" and "social research" have both gained a degree of autonomy since their origination in classical sociology. The distinct field of social anthropology or anthroposociology is the dominant constituent of anthropology throughout the United Kingdom and Commonwealth and much of Europe (France in particular),[170] where it is distinguished from cultural anthropology.[171] In the United States, social anthropology is commonly subsumed within cultural anthropology (or under the relatively new designation of sociocultural anthropology).[172]
Sociology and applied sociology are connected to the professional and academic discipline of social work.[173] Both disciplines study social interactions, community and the effect of various systems (i.e. family, school, community, laws, political sphere) on the individual.[174] However, social work is generally more focused on practical strategies to alleviate social dysfunctions; sociology in general provides a thorough examination of the root causes of these problems.[175] For example, a sociologist might study why a community is plagued with poverty. The applied sociologist would be more focused on practical strategies on what needs to be done to alleviate this burden. The social worker would be focused on action; implementing theses strategies "directly" or "indirectly" by means of mental health therapy, counselling, advocacy, community organization or community mobilization.[174]
Social anthropology is the branch of anthropology that studies how contemporary living human beings behave in social groups. Practitioners of social anthropology, like sociologists, investigate various facets of social organization. Traditionally, social anthropologists analyzed non-industrial and non-Western societies, whereas sociologists focused on industrialized societies in the Western world. In recent years, however, social anthropology has expanded its focus to modern Western societies, meaning that the two disciplines increasingly converge.[176][173]
Sociocultural anthropology, which includes linguistic anthropology, is concerned with the problem of difference and similarity within and between human populations. The discipline arose concomitantly with the expansion of European colonial empires, and its practices and theories have been questioned and reformulated along with processes of decolonization. Such issues have re-emerged as transnational processes have challenged the centrality of the nation-state to theorizations about culture and power. New challenges have emerged as public debates about multiculturalism, and the increasing use of the culture concept outside of the academy and among peoples studied by anthropology. These times are not "business-as-usual" in the academy, in anthropology, or in the world, if ever there were such times.[citation needed]
Irving Louis Horowitz, in his The Decomposition of Sociology (1994), has argued that the discipline, while arriving from a "distinguished lineage and tradition", is in decline due to deeply ideological theory and a lack of relevance to policy making: "The decomposition of sociology began when this great tradition became subject to ideological thinking, and an inferior tradition surfaced in the wake of totalitarian triumphs."[177] Furthermore: "A problem yet unmentioned is that sociology's malaise has left all the social sciences vulnerable to pure positivism—to an empiricism lacking any theoretical basis. Talented individuals who might, in an earlier time, have gone into sociology are seeking intellectual stimulation in business, law, the natural sciences, and even creative writing; this drains sociology of much needed potential."[177] Horowitz cites the lack of a 'core discipline' as exacerbating the problem. Randall Collins, the Dorothy Swaine Thomas Professor in Sociology at the University of Pennsylvania and a member of the Advisory Editors Council of the Social Evolution & History journal, has voiced similar sentiments: "we have lost all coherence as a discipline, we are breaking up into a conglomerate of specialities, each going on its own way and with none too high regard for each other."[178]
In 2007, The Times Higher Education Guide published a list of 'The most cited authors of books in the Humanities' (including philosophy and psychology). Seven of the top ten are listed as sociologists: Michel Foucault (1), Pierre Bourdieu (2), Anthony Giddens (5), Erving Goffman (6), Jürgen Habermas (7), Max Weber (8), and Bruno Latour (10).[179]
Journals
For a more comprehensive list, see List of sociology journals.
The most highly ranked general journals which publish original research in the field of sociology are the American Journal of Sociology and the American Sociological Review.[180] The Annual Review of Sociology, which publishes original review essays, is also highly ranked.[180] Many other generalist and specialized journals exist.
See also
icon Society portal
Bibliography of sociology
Critical juncture theory
Cultural theory
Engaged theory
History of the social sciences
List of sociologists
Outline of sociology
Political sociology
Post-industrial society
Social theory
Social psychology
Sociological Francoism
Notes
See Branches of the early Islamic philosophy.
See also Fauré, Christine, and Jacques Guilhaumou. 2006. "Sieyès et le non-dit de la sociologie: du mot à la chose." Revue d'histoire des sciences humaines 15. Naissances de la science sociale. See also the article 'sociologie' in the French-language Wikipedia.
The normal distribution is important in many fields of science, not just the social sciences
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