Vegetarian nutrition is the set of health-related challenges and advantages of vegetarian diets.
Well-planned vegetarian and vegan diets are nutritionally adequate and are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence. A vegetarian diet can provide adequate protein, iron, zinc, vitamin B12, and calcium intake, though these nutrients can be relatively low in poorly planned vegetarian diets, particularly when not enough calories are consumed.
Evidence suggests that vegetarians have lower rates of coronary heart disease, obesity, hypertension, type 2 diabetes, osteoporosis, and dementia. Vegetarian diets tend to be rich in carbohydrates, omega-6 fatty acids, dietary fibre, carotenoids, folic acid, vitamin C, vitamin E, potassium and magnesium. They are generally low in saturated fat, cholesterol, and animal protein.
Benefits of a vegetarian diet 
The Oxford Vegetarian Study showed that the health of vegetarians compares favourably with that of meat-eaters (excluding pescetarians). British vegetarians have lower death rates than non-vegetarians, although this is at least partly due to non-dietary lifestyle factors, such as a low prevalence of smoking and the generally high socioeconomic status of vegetarians, or to aspects of the diet other than the avoidance of meat and fish.
Loma Linda University School of Public Health has conducted three cohort studies that identify the health benefits of a vegetarian diet. The University is a Seventh-day Adventist health science institution. The first study, funded by the US Public Health Service in 1958 and limited to Adventists in California, included many vegetarians. The next cohort of California Adventists, the Adventist Health Study-1 (AHS-1), collected data from 1974 to 1976. From 2002 to 2007 the Adventist Health Study-2 (AHS-2) collected dietary data from 96,000 church members from the United States and Canada. Many scientific articles have been published on the health and nutrition properties of a vegetarian diet from these cohort studies. The most recent AHS-2 study includes findings on metabolic syndrome, Vitamin D absorption and type-2 diabetes
In prospective studies of adults, compared to non-vegetarian eating patterns, vegetarian-style eating patterns have been associated with improved health outcomes—lower levels of obesity, a reduced risk of cardiovascular disease, and lower total mortality. Several clinical trials have documented that vegetarian eating patterns lower blood pressure.
On average, vegetarians consume a lower proportion of calories from fat (particularly saturated fatty acids); fewer overall calories; and more fiber, potassium, and vitamin C than do non-vegetarians. Vegetarians generally have a lower body mass index. These characteristics and other lifestyle factors associated with a vegetarian diet may contribute to the positive health outcomes that have been identified among vegetarians.
Vegetarians may avoid the negative health effects of red meat: A 1999 meta-study of five studies comparing vegetarian and non-vegetarian mortality rates in Western countries found that in comparison with regular meat eaters, mortality from ischemic heart disease was 34% lower in people who ate fish but not meat (pescetarians), 34% lower in ovo-lacto vegetarians, 26% lower in vegans and 20% lower in occasional meat eaters.
Doctors Dean Ornish, T. Colin Campbell, John A. McDougall, Caldwell Esselstyn and Neal D. Barnard claim that high animal fat and protein diets, such as the standard American diet, are detrimental to health. They also state that a lifestyle change incorporating a low fat vegetarian or vegan diet could not only prevent various degenerative diseases, such as coronary artery disease, but reverse them.
Studies of cancer have not shown clear differences in cancer rates between vegetarians and non-vegetarians. There is evidence that vegetarians tend to have a lower body mass index, lower risk of obesity, lower blood cholesterol levels, lower homocysteine levels, lower risk of high blood pressure, and lower risk of type 2 diabetes. One large prospective study found that non-meat-eaters had only half the risk of meat eaters of requiring an emergency appendectomy.
Vegetarians are less likely to die by choking on food since the most common food to obstruct the airway is fish, which caused about 4,500 accidents a year in the UK as of 1998. Meat, poultry and bones were cited as the next three most common causes of choking, followed by sweets and non-food objects.
Potential nutrient deficiencies 
Poorly planned vegetarian diets may be low in vitamin B12, calcium, omega-3 fatty acids, vitamin D, iron, zinc, riboflavin (vitamin B2), and iodine, and poorly planned vegan diets may have particularly low intakes of vitamin B12 and calcium. Nonetheless, well-balanced vegetarian and vegan diets can meet all these nutrient requirements and are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence. Many tools are available to help vegetarians maintain an adequate nutrient balance including several Vegetarian Diet Pyramids.
The typical vegetarian gets adequate protein as long as caloric intake is adequate and a variety of foods is eaten. Vegetarian diets tend to be lower in protein than non-vegetarian diets but typically meet or exceed daily protein intake recommendations, which is believed to be beneficial. Plant sources of protein include soy beans (and soy products such as tofu, veggie burgers, soy milk, etc.), other legumes, nuts and seeds, and grains.
Combining proteins 
Despite a widespread belief that vegetarians must eat grains and beans within a few hours of each other to make a 'complete' protein which contains all 9 "essential amino acids", this has never been substantiated by research. The protein-combining theory was brought to popular attention in Frances Moore Lappé's 1971 bestseller Diet for a Small Planet. In later editions of the book, as early as 1981, Lappé withdrew her contention that protein 'combining' is necessary.
In several studies, vegans and other vegetarians were not found to suffer from iron-deficiency more than non-vegetarians. However, while one study agreed that iron-deficiency anemia is not more common among vegetarians, they found "vegetarian children had ... reduced levels of haemoglobin and iron compared to omnivores" due "to the absence of animal iron sources with high utilizability". Another study, in India, found that "strict vegetarian mothers as well as their newborns have a greater incidence and risk of anemia and iron deficiency."
The recommended iron intake for vegetarians is 1.8 times that of nonvegetarians, because plants, dairy, and eggs contain only non-heme iron, and this is absorbed less efficiently than heme iron. Although a lower percentage of non-heme iron is absorbed, greater amounts of non-heme iron are concentrated in many non-meat sources of iron (than the amount of iron per serving in meats), and therefore, cereals, eggs, nuts, seeds, and legumes (including soy foods, peas, beans, chickpeas, and lentils) are significant sources of iron, and a well-planned vegetarian diet should not lead to iron deficiency, but fruitarianism and raw foods diets should not be pursued for infants or children. Meat, fish, and poultry (not dairy or eggs) are the only sources of heme iron; intake of heme iron may be associated with colon cancer. Non-heme iron is more sensitive to both inhibitors and enhancers of iron absorption. Vitamin C is an iron absorption enhancer. The main inhibitors for most people are phytates (e.g. legumes and grains), but other inhibitors include tannins (tea, wine), calcium and polyphenols.
Iron is an integral part of many proteins and enzymes which maintain good health. In humans, iron is an essential component of proteins involved in red blood cells' oxygen transport. Iron also helps regulate cell growth and differentiation.
Western vegetarians and vegans have not been found to suffer from overt zinc deficiencies any more than meat-eaters. However, phytates in many whole-grains and fiber in many foods may interfere with zinc absorption and marginal zinc intake has poorly understood effects. Vegetarians may need more than the US RDA (15 mg) of zinc daily if their diet is high in phytates.
Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soyfoods, nuts, peas, and seeds.
Vitamin B12 
Lacto-ovo vegetarians may get vitamin B12 from eggs and dairy products (milk, cheese, etc.); for some this is adequate but some may still remain B12-deficient. The world's largest group of professional dietitians says the form of vitamin B12 sourced from animal-products is protein-bound and not as easily digested, especially as people age, and therefore recommends B12 supplementation for everyone over the age of 50. Pregnant and lactating vegetarians (and breastfed infants if the mother's diet is not supplemented) should also use supplements, whether pills, injections, or B12-fortified foods, if they don't get adequate B12 from animal-products like eggs or dairy.
Generally, humans need 2.4-3 micrograms of B12 each day. Although some argue that developing a disease from B12 deficiency by following a sensible diet is extremely rare—less than one chance in a million, there are cases to suggest that vegetarians and vegans who are not taking vitamin B12 supplements or food fortified with B12, do not consume sufficient servings of B12 and have abnormally low blood concentrations of vitamin B12. This is because, unless fortified, plant foods do not contain reliable amounts of active vitamin B12.
It is essential, therefore, that vegetarians consume adequate amounts of dietary supplements or foods that have been fortified with B12 (such as nutritional yeast or other yeast extracts, vegetable stock, veggie burger mixes, textured vegetable protein, soy milks, vegetable and sunflower margarines, and breakfast cereals). B12 that is to be used in these supplements is typically grown from vegan sources (such as bacteria). Soybean and barley seeds grown in soils amended with cow dung (which is naturally rich in B12), or with pure B12 had a higher B12 content than those grown without this supplementation. There is a patent for cultivating plants in a solution containing vitamin B12 so that the crop contains more B12.
Omega-3 fatty acids 
Vegetarian diets can be low in omega-3 fatty acids (O3FA). Major vegetarian sources of O3FA include algae, hempseeds and hempseed oil, walnuts, flaxseeds and flaxseed oil, olive oil, canola (rapeseed) oil, avocado and chia seeds. However, diets lacking fish, eggs, or generous amounts of sea vegetables (seaweed) generally lack a direct source of long-chain O3FA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Vegetarian diets may also have a high ratio of O6FA to O3FA, which inhibits the conversion of short-chain fatty acids such as alpha-Linolenic acid (ALA), found in most vegetarian O3FA sources, to EPA and DHA. Short-term supplemental ALA has been shown to increase EPA levels but not DHA levels, suggesting poor conversion of the intermediary EPA to DHA. DHA supplements derived from DHA-rich microalgae are available, and the human body can also convert DHA to EPA.
While there is no scientific consensus on the role of omega-3 fatty acids, they may reduce the risk of coronary heart disease, lower triglycerides, stabilize mood and help prevent depression, help reduce symptoms of ADD, reduce joint pain and other rheumatoid problems, and reduce the risk of dementia in older age. While there is little evidence of adverse health or cognitive effects due to DHA deficiency in adult vegetarians or vegans, fetal and breast milk levels remain a concern. EPA and DHA supplementation has been shown to reduce platelet aggregation in vegetarians, but a direct link to cardiovascular morbidity and mortality, which is already lower for vegetarians, has yet to be determined.
Vitamin D 
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., those 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.
One study reported 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." Iodine, however, is usually supplied by iodized salt and other sources in first world countries. Other significant sources of iodine include sea vegetables (seaweed) and bread made with dough conditioners.
See also 
- “Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets”. Journal of the American Dietetic Association, 2003, 06. Retrieved 13 April 2012.
- Incidence of osteoporosis in vegetarians and omnivores
- The Incidence of Dementia and Intake of Animal Products: Preliminary Findings from the Adventist Health Study
- Appleby PN, Thorogood M, Mann JI, Key TJ: “The Oxford Vegetarian Study: an overview”. American Journal of Clinical Nutrition, 1999, 70:525S-531S.
- Appleby, PN, Key, TJ, Thorogood, M, Burr, ML, Mann, J. "Mortality in British vegetarians". Public Health Nutrition 2002 (5): 29–36.
- Adventist Health Studies
- List of scientific publications from the Adventist Health Studies
- Rizzo N, et al. Vegetarian dietary patterns are associated with a lower risk of metabolic syndrome: the Adventist Health Study-2. Diabetes Care. 2011 May;34(5):1225-7.
- Chan J, et al. Serum 25-hydroxyvitamin D status of vegetarians, partial vegetarians, and nonvegetarians: the Adventist Health Study-2. Am J Clin Nutr. 2009 May;89(5):1686S-1692S.
- Tonstad S, et al. Type of Vegetarian Diet, Body Weight, and Prevalence of Type 2 Diabetes. Diabetes Care. 2009 May;32(5):791-6.
- Key TJ, Fraser GE, Thorogood M, Appleby PN, Beral V, Reeves G, Burr ML, Chang-Claude J, Frentzel-Beyme R, Kuzma JW, Mann J, McPherson K: “Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies”. American Journal of Clinical Nutrition, 1999, 70:516S-524S. http://www.ajcn.org/cgi/content/full/70/3/516S
- Segelken, Roger (2001-06-28). "China Study II: Switch to Western diet may bring Western-type diseases". Cornell Chronicle. Retrieved 2006-09-15.
- "China-Cornell-Oxford Project On Nutrition, Environment and Health at Cornell University". Division of Nutritional Sciences. Cornell University. Retrieved 2006-09-15.
- Barnard, Neal D. (2007). Dr. Neal Barnard's Program for Reversing Diabetes. New York: Rodale. pp. 40–50. "Set aside animal products"
- Ornish D, Brown SE, Scherwitz LW, et al. (July 1990). "Can lifestyle changes reverse coronary heart disease? The Lifestyle Heart Trial". Lancet 336 (8708): 129–33. doi:10.1016/0140-6736(90)91656-U. PMID 1973470.
- Campbell TC, et al. (Oct 2002). "Medically supervised water-only fasting in the treatment of borderline hypertension". J Altern Complement Med. 8 (5): 643–50. doi:10.1089/107555302320825165. PMID 12470446.
- McDougall J, et al. (Feb 2002). "Effects of a very low-fat, vegan diet in subjects with rheumatoid arthritis". J Altern Complement Med. 8 (1): 71–5. doi:10.1089/107555302753507195. PMID 11890437.
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- Home and leisure accident report Summary of 1998 data p.16 Department of Trade and Industry (UK)
- Dolkas, Laura; Stanley, Christina; Smith, Alan M.; Vilke, Gary M.: "Deaths Associated with Choking in San Diego County" (Abstract). Journal of Forensic Sciences, January 2007, 52:176-179.
- Loma Linda University Vegetarian Food Pyramid
- The Oldways Vegetarian Diet Pyramid
- Akers, Keith: But How Do You Get Enough Protein?. Compassionate Spirit. Retrieved 25 June 2010.
- Food Navigator USA: Low-protein diets could protect against cancer, says new study. 7 December 2006. Retrieved 4 January 2007.
- Diabetic nephropathy
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- Alleyne, Richard (2009-12-03). "Vegetarian low protein diet could be key to long life". The Telegraph. Retrieved 2010-04-24.
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- Lappé, Frances Moore (1981). Diet for a Small Planet, p. 162. ISBN 0-345-32120-0
- see: (1.) [Larsson CL, Johansson GK. Dietary intake and nutritional status of young vegans and omnivores in Sweden. Am J Clin Nutr. 2002;76:100–106. MEDLINE | http://www.adajournal.org/medline/record/ivp_00029165_76_100]. (2.) Messina MJ, Messina VL. The Dietitian's Guide to Vegetarian Diets: Issues and Applications. Gaithersburg, MD: Aspen Publishers; 1996. (3.) Am J Clin Nutr. 1994;59 (suppl):1233S-1237S. (4.) [ Ball MJ, Bartlett MA. Dietary intake and iron status of Australian vegetarian women. Am J Clin Nutr. 1999;70:353–358. | http://www.adajournal.org/medline/record/ivp_00029165_70_353]
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- D. C. Sharma1 Contact Information, Raj Kiran, Vijaywantee Ramnath, Krishna Khushiani and P. P. Singh: “Iron deficiency and anemia in vegetarian mothers and their newborns .” Indian Journal of Clinical Biochemistry, Volume 9, Number 2 / December, 1994, 100-102.
- Nutrition Australia: FAQ on Vegetarian Diets'.' Retrieved 11 April 2007.
- see: (1) http://cebp.aacrjournals.org/cgi/content/abstract/15/11/2274 | Cancer Epidemiology Biomarkers & Prevention Vol. 15, 2274-2279, November 2006
- Freeland-Graves, J. H., Bodzy, P. W., Epright, M. A. "Zinc status of vegetarians". Journal of the American Dietetic Association 1980 (77): 655–661.
- The Vegetarian Society. Information Sheet: Vitamin B12. Retrieved 26 April 2007.
- "Dietary Supplement Fact Sheet: Vitamin B12". USA.gov. Office of dietary supplements. Retrieved 14 March 2012.
- "Vitamin B12 Deficiency—the Meat-eaters’ Last Stand". McDougall Newsletter Archive Vol. 6, No. 11. Dr. McDougall. Retrieved 14 March 2012.
- "Vegans and the Vitamin B12 Deficiency Myth". Vegetarianism. pamrotella. Retrieved 14 March 2012.
- "Worried About Vitamin B12 Deficiency?". Raw Food Health. RAW FOOD HEALTH. Retrieved 14 March 2012.
- See, for example, Hokin BD and Butler T: “Cyanocobalamin (vitamin B-12) status in Seventh-day Adventist ministers in Australia” in American Journal of Clinical Nutrition, September 1999, 70:576S-578S; and Krajcovicova-Kudlackova M, Blazicek P, Kopcova J, Bederova A and Babinska K: “Homocysteine Levels in Vegetarians versus Omnivores” in Annals of Nutrition & Metabolism, 2000, 44:135-138; and VeganHealth.org: B12 and Chronic Disease: Homocysteine. Retrieved 26 April 2007.
- Mozafar, A. 1994. Enrichment of some B-vitamins in plants with application of organic fertilizers (and/or manufacture by bacteria in healthy, cobalt-replete soil), Plant and Soil 167:305-311. http://www.springerlink.com/content/m34328h82716261u/fulltext.pdf
- Seed and plant containing vitamin B12 and method of producing the same
- Sanders, Thomas A.B. (August–September 2009). "DHA status of vegetarians". Prostaglandins, Leukotrienes, and Essential Fatty Acids (International Society for the Study of Fatty Acids and Lipids) 81 (2–3): 137–141. doi:10.1016/j.plefa.2009.05.013. ISSN 0952-3278. PMID 19500961.
- http://content.health.msn.com/content/article/91/101125.htm?GT1=5100[dead link]
- Mezzano, Diego; Karin Kosiel, Carlos Martínez, Ada Cuevas, Olga Panes, Eduardo Aranda, Pablo Strobel, Druso D. Pérez, Jaime Pereira, Jaime Rozowski and Federico Leighton (1 November 2000). "Cardiovascular Risk Factors in Vegetarians: Normalization of Hyperhomocysteinemia with Vitamin B12 and Reduction of Platelet Aggregation with n-3 Fatty Acids". Thrombosis Research 100 (3): 153–160. doi:10.1016/S0049-3848(00)00313-3. PMID 11108902.
- Thomas Remer, Annette Neubert and Friedrich Manz: “Increased risk of iodine deficiency with vegetarian nutrition”. British Journal of Nutrition, 1999, 81:45-49. Retrieved 4 January 2007.
Further reading 
- William Harris (1993) Scientific Basis of Vegetarianism
- George Eisman (1999) A Basic Course in Vegetarian and Vegan Nutrition
- Joan Sabaté (2001) Vegetarian Nutrition
- United States Department of Agriculture. Vegetarian Diets.
- Food and Nutrition Information Center, USDA. Vegetarian Nutrition Resource List.
- Mayo Clinic. Vegetarian diet: How to get the best nutrition.
- Medline Plus. Vegetarian Diet.
- International Congress on Vegetarian Nutrition.
- Vegetarian Nutrition Dietetic Practice Group.
- The Vegetarian Society of the United Kingdom.