A healthy diet is one that is arrived at with the intent of improving or maintaining optimal health.

This usually involves consuming nutrients by eating the appropriate amounts from all of the food groups, including an adequate amount of water. Since human nutrition is complex, a healthy diet may vary widely, and is subject to an individual's genetic makeup, environment, and health. For around 20% of the human population, lack of food and malnutrition are the main impediments to healthy eating. Conversely, people in developed countries have the opposite problem; they are more concerned about obesity.

Nutritional overview

Fresh vegetables are common in a healthy diet.

1. Sufficient calories to maintain a person's metabolic and activity needs, but not so excessive as to result in fat storage greater than roughly 30% of body mass. For most people the recommended daily allowance of energy is 2,000 calories, but it depends on age, sex, height, weight, and physical activity. (see Body fat percentage)
2. Sufficient quantities of fat, including monounsaturated fat, polyunsaturated fat and saturated fat, with a balance of omega-6 and long-chain omega-3 lipids. The recommended daily allowance of fat is 65-80 grams.
3. Maintenance of a good ratio between carbohydrates and lipids (4:1): four grams of the first for one gram of the second.
4. Avoidance of excessive saturated fat (20grams recommended limit, although the "evidence" for this claim is forever in debate after the testimony of results provided by the Framingham Heart Study of 1948-1998)
5. Avoidance of trans fat.
6. Sufficient essential amino acids ("complete protein") to provide cellular replenishment and transport proteins. All essential amino acids are present in animals. A select few plants (such as soy and hemp) give all the essential acids. A combination of other plants may also provide all essential amino acids (except rice and beans which have limitations).
7. Essential micronutrients such as vitamins and certain minerals.
8. Avoiding directly poisonous (e.g. heavy metals) and carcinogenic (e.g. benzene) substances;
9. Avoiding foods contaminated by human pathogens (e.g. E. coli, tapeworm eggs);
10. Avoiding chronic high doses of certain foods that are benign or beneficial in small or occasional doses, such as
    • foods that may burden or exhaust normal functions (e.g. refined carbohydrates without adequate dietary fiber);
    • foods that may interfere at high doses with other body processes (e.g. refined table salt);
    • foods or substances with directly toxic properties at high chronic doses (e.g. ethyl alcohol).

Detrimental eating habits

In specific individuals, ingesting foods containing natural allergens (e.g. peanuts, shellfood) or drug-induced triggers (e.g. tyramine for a person taking an MAO inhibitor) may be life-threatening.

Some foods have low nutritional value, and if consumed on a regular basis will contribute to the decline of human health. This has been demonstrated by various epidemiological studies that have determined that foods such as processed and fast foods are linked to diabetes and various heart problems.

When improperly cut or prepared, a small number of foods (such as fugu) can result in death.

The ingredient usually cited as being most crucial to good health, water, has even been known to result in death when consumed in extraordinary quantities.

Cultural and psychological factors

From a psychological perspective, a new healthy diet may be difficult to achieve for a person with poor eating habits. This may be due to tastes acquired in early adolescence and preferences for fatty foods. It may be easier for such a person to transition to a healthy diet if treats such as chocolate are allowed; sweets may act as mood stabilizers, which could help reinforce correct nutrient intake.

It is known that the experiences we have in childhood relating to consumption of food affect our perspective on food consumption in later life. From this, we are able to determine ourselves our limits of how much we will eat, as well as foods we will not eat - which can develop into eating disorders, such as anorexia, bulimia, or orthorexia This is also true with how we perceive the sizes of the meals or amounts of food we consume daily; people have different interpretations of small and large meals based on upbringing.

While plants, vegetables, and fruits are known to help reduce the incidence of chronic disease, the benefits on health posed by plant-based foods, as well as the percentage of which a diet needs to be plant based in order to have health benefits is unknown. Nevertheless, plant-based food diets in society and between nutritionist circles are linked to health and longevity, as well as contributing to lowering cholesterol, weight loss, and in some cases, stress reduction.

Indeed, ideas of what counts as "healthy eating" have varied in different times and places, according to scientific advances in the field of nutrition, cultural fashions, religious proscriptions, or personal considerations.

Public policy issues

Fears of high cholesterol were frequently voiced up until the mid-1990s. However, more recent research has shown that the distinction between high- and low-density lipoprotein ('good' and 'bad' cholesterol, respectively) must be addressed when speaking of the potential ill effects of cholesterol. Low-density lipoprotein is often prevalent in animal products, such as bacon and egg yolks, whereas high-density lipoprotein is more common in plant and fish tissues, such as olive oil and salmon.

Media coverage of mass-produced, processed, "snack" or "sweet" products directly marketed at children has worked to undermine policy efforts to improve eating habits. The main problem with such advertisements for foods is that alcohol and fast food are portrayed as offering excitement, escape and instant gratification.

Particularly within the last five years government agencies have attempted to combat the amount and method of media coverage lavished upon "junk" foods. Governments also put pressure on businesses to promote healthy food options, consider limiting the availability of junk food in state-run schools, and tax foods that are high in fat. Most recently, the United Kingdom removed the rights for McDonald's to advertise its products as the majority of the foods that were seen to have low nutrient values were aimed at children under the guise of the "Happy Meal". The British Heart Foundation released its own government-funded advertisements, labeled "Food4Thought", which were targeted at children and adults displaying the gory nature of how fast food is generally constituted.

Food additive controversy

Some claim that food additives, such as artificial sweeteners, colorants, preserving agents, and flavorings may cause health problems such as increasing the risk of cancer or ADHD. Examples of fast food critics include Morgan Spurlock and Eric Schlosser.

See also

• Diet and cancer
• Diet and heart disease
• Diet (multiple sclerosis)
• Health food
• Nutrigenomics
• Nutritional genomics
• Standard American Diet
• Red meat

References

1. MAFF (Ministry of Agriculture, Fisheries and Food) 1990: Eight Guidelines for a healthy diet London: Food Sense
2. Barasi, Mary E. (2003) Human Nutrition: A Health Perspective London:Arnold
3. Mcdonalds Corporation Quality & Nutrition information - McDonalds USA Big-Mac Nutrition factsheet Mcdonalds Corporation (http://app.mcdonalds.com/bagamcmeal?process=item&itemID=5)
4. Spurlock, M. Supersize Me - A film of epic Proportions Columbia Tristar
5. Nestle, M. (1998) Animal v plant foods in human diets and health - Proceedings of the Nutrition Society
6. National Health Service (2005) Five a day - a guide to healthy eating NHS Press (http://www.5aday.nhs.uk/)
7. Johnson, R. K. (2000). The 2000 Dietary Guidelines for Americans: foundation of US nutrition policy. - British Nutrition Foundation Nutrition Bulletin 25. p241-248
8. Achterberg, C., McDonnell, E., Fagby, R. (1994) How to put the Food Guide Pyramid into practice - Jornal of the American Dietetic Association Volume 94 p 1030-1035
9. United Kingdom Department of Health (2005): Choosing Health: making healthier choices easier -- Public Health White Paper CM 6374 retrieved from: United Kingdom Department of Health Website
10. United States Department of Agriculture (2005) . MyPyramid - Guidelines for healthy eating - Dietary guidelines for Americans USDA Press/Printing retrieved from United States Department of agriculture - MyPyramid replaces food pyramid guide
11. Oliver, J., Channel Four (2005) Jamie's School Dinners - Documentary produced for channel four Television Programme.
12. Food standards Authority (2005) 8 easy steps to keeping a healthy and balanced diet - Eat well, be well retrieved from Eat well, be well website.
13. National Cancer Institute (2005) Eat five to Nine servings of fruits and vegetables per day retrieved from 5-a-day National Cancer institute
14. British Heart Foundation (2005). Food4Thought - Campaign against junk food within children's diets. retrieved from British Heart Foundation Food4Thought

External links

• United Kingdom's Food Standards Agency recommendations on a healthy diet
• Diet, Nutrition and the prevention of chronic diseases, by a Joint WHO/FAO Expert consultation (2003)
• ''Healthy Children, Healthy Choices'', from the Center for Disease Control's website
• Making Healthy Food Choices; guidelines for heart healthy eating from the American Heart Association
• US Department for Health & Human services recommendations on a healthy diet for women
• Mayo Clinic Healthy Weight Pyramid
• British Nutrition Foundation

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