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Vegetarian nutrition is the set of health-related challenges and advantages of vegetarian diets.
According to the American Dietetic Association (ADA), American Heart Association, National Institutes of Health, British Medical Association and the Mayo Clinic, vegetarian diets may offer a number of health benefits compared to non-vegetarian diets.
According to research dating to as early as the late 19th Century (surveyed and improved by Dr. Kellogg in Autointoxication, 1918 and Natural Diet of Man, 1923) American vegetarians tend to have lower body mass indices, lower levels of cholesterol, lower blood pressure, and less incidence of heart disease, hypertension, some forms of cancer, type 2 diabetes, renal disease, osteoporosis, dementias such as Alzheimer’s Disease and other disorders that may be diet-related. The health of a cohort of 27,000 vegetarians is currently being followed at a UK centre of the European Prospective Investigation into Cancer and Nutrition (EPIC), the largest study of the long-term effects of vegetarian diet.
For vegetarians there are foods that a consensus of medical dietitians advise should be supplemented or concentrated upon. These foods are especially recommended for vegans, fruitarians, raw-foodists, macrobiotics and other "restrictive" forms of vegetarianism.
The typical vegetarian gets adequate protein as long as caloric intake is adequate and a variety of foods are eaten. A typical vegetarian gets less protein than the typical non-vegetarian which may be beneficial. USDA's tables provide information about the protein content of most foods, and the Institute of Medicine's DRI tables show the amount of recommended protein intake.
Due to the lower digestability of plant proteins, however, the ADA states "protein needs might be higher than the RDA in vegetarians whose dietary protein sources are mainly those that are less well digested, such as some cereals and legumes.".
A widely held myth in the United States about protein - and vegetarianism itself - is the idea of protein combining: that vegetarians must eat grains and beans within a few hours of each other in order to make a 'complete' protein which contains all 8 "essential amino acids". While this myth is widely believed, it has never been substantiated by research.
The protein combining myth was brought to popular attention in Frances Moore Lappe's 1971 besteller Diet for a Small Planet. In later editions of the book, as early as 1981, Lappe reversed her opinion that protein 'combining' is necessary. John McDougall MD, in The McDougall Plan concurs with Lappe's 1981 conclusion, providing a table comparing amino acid requirements with the amino acids in common plant foods. McDougall says "many people believe that animal foods contain protein that is superior in quality to the protein found in plants. This is a misconception dating back to 1914, when Osborn and Mendel studied the protein requirements of laboratory rats. (11) ... It has since been shown that the initial premise that animal products supplied the most ideal protein pattern for humans, as it did for rats, was incorrect."McDougall still challenges those who perpetuate the protein-combining myth by demanding that they produce evidence to support their claims.
A study in the Journal of the American Dietetic Association found that while iron deficiency anemia is not more common among vegetarians, "Vegetarian children had ... reduced levels of haemoglobin and iron compared to omnivores" due "to the absence of animal iron sources with high utilizability".
Meat, fish and poultry are the only sources of heme iron; plants contain non-heme iron. The human body absorbs non-heme iron less efficiently.
Western vegetarians and vegans have not been found to suffer from overt zinc deficiencies any more than meat-eaters. However, phylate in many whole-grains and fiber in many foods may interfere with zinc absorption and marginal zinc intake has poorly understood effects.
One of the concerns of a vegetarian diet is that plant foods do not contain vitamin B12 except when they are contaminated by microorganisms or have vitamin B12 added to them. Lack of Vitamin B12 causes anemia and this vitamin is produced only by bacteria which are found only in animals.
The only reliable unfortified sources of vitamin B12 are meat, dairy products and eggs. According to the USDA, strict vegetarians and people above 50 are at the highest risk of not getting enough vitamin B12.
Animals, including humans, must ingest B12 to maintain proper B12 levels. Numerous studies demonstrate that vegetarians who are not taking B12 supplements can improve their health by improving their B12 status.
Omega-3 fatty acids
Vegetarian sources of Omega-3 fatty acids include flaxseeds and flaxseed oil, olive oil,walnuts, canola (rapeseed) oil, avocado, and eggs.
Vegetarian sources of omega-3 fatty acids are primarily the short chain variety and likely to have lower concentrations of the particular essential fatty acids (EFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The body can synthesize small quantities of EPA and DHA from other omega-3 fatty acids, such as alpha-linolenic acids, which are present in vegetarian sources of omega-3 fatty acids.
The human body can also convert DHA into EPA. DHA supplements derived from DHA-rich microalgae are available. Whilst the human body can in theory do this conversion, in practice modern diets and lifestyles reduce the effectiveness of the conversion systems. Roughly ten times more of the short chain omega-3s must be consumed to have the same effect as the long chain form from fish oil.
While there is no scientific consensus on the role of omega-3 fatty acids, it is generally believed that they may reduce the risk of coronary heart disease, lower triglycerides, stabilize mood and help prevent depression, help prevent ADD, reduce joint pain and other rheumatoid problems and reduce the risk of dementia in older age.
The human body can synthesize Vitamin D when skin is exposed to ultraviolet radiation from the sun. Vegans who do not eat foods or pills fortified with synthetic vitamin D and with little exposure to the sun's ultraviolet radiation, e.g. who don't expose their extremities for at least 15-30 minutes per day or those living at latitudes close to the poles, are vulnerable to Vitamin D deficiencies.
Vitamin D acts as a hormone, sending a message to the intestines to increase the absorption of calcium and phosphorus, which produces strong bones. Vitamin D also works in concert with a number of other vitamins, minerals, and hormones to promote bone mineralization. Research also suggests that vitamin D may help maintain a healthy immune system and help regulate cell growth and differentiation.
According the British Journal of Nutrition there is a "potential danger of (Iodine) deficiency disorders due to strict forms of vegetarian nutrition, especially when fruits and vegetables grown in soils with low (Iodine) levels are ingested."
- Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets
- Mayo Clinic's synopsis.
- Vegetarian Resource Group
- Veg News
- American Heart Association
- Simple Vegetarian Recipes
- Protein Basics Chart: tells how much and what kinds of proteins are required for different lifestyles and has great detailed charts showing how much protein is in various foods.
- Focus on vegetarians research from EPIC-Oxford.
- The China Study : The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss and Long-Term Health (2005) by: T. Colin Campbell ISBN 1-932100-66-0
- Becoming a 'Veggie' : The Smart Move
- ^ Low-protein diets could protect against cancer, says new study
- ^ Diabetic nephropathy
- ^ American Dietetic Association on vegetarian nutrition
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- ^ Freeland-Graves J. H., Bodzy P. W., Epright M. A. Zinc status of vegetarians. J. Am. Diet. Assoc. 1980;77:655-661
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- ^ Callender S. T., Spray G. H.; Latent pernicious anemia. Br. J. Haematol. 1962; 8: 230-240
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- Vegetarian cuisine
- Vegan cuisine