Health benefits and concerns
The American Dietetic Association and Dietitians of Canada have stated that at all stages of life, a properly planned vegetarian diet is "healthful, nutritionally adequate, and provides health benefits in the prevention and treatment of certain diseases". Large-scale studies have shown that mortality from ischaemic heart disease was 30% lower among vegetarian men and 20% lower among vegetarian women than in nonvegetarians.[18][19][20] Necessary nutrients, proteins, and amino acids for the body's sustenance can be found in vegetables, grains, nuts, soymilk, eggs and dairy.[21] Vegetarian diets offer lower levels of saturated fat, cholesterol, and animal protein, and higher levels of carbohydrates, fibre, magnesium, potassium, folate, and antioxidants such as vitamins C and E and phytochemicals.[22]
Vegetarians tend to have lower body mass index, lower levels of cholesterol, lower blood pressure, and less incidence of heart disease, hypertension, type 2 diabetes, renal disease, osteoporosis, dementias such as Alzheimer’s Disease and other disorders.[23] Non-lean red meat, in particular, has been found to be directly associated with increased risk of cancers of the esophagus, liver, colon, and the lungs.[24] Other studies have shown no significant differences between vegetarians and nonvegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, breast cancer, or prostate cancer, although the sample of vegetarians was small and included ex-smokers who had switched their diet within the last five years.[19] A 2010 study compared a group of vegetarian and meat-eating Seventh Day Adventists in which vegetarians scored lower on depression tests and had better mood profiles.[25]
Protein intake in vegetarian diets is only slightly lower than in meat diets and can meet daily requirements for any person, including athletes and bodybuilders.[28] Studies at Harvard University as well as other studies conducted in the United States, United Kingdom, Canada, Australia, New Zealand and various European countries, have confirmed that vegetarian diets provide sufficient protein intake as long as a variety of plant sources are available and consumed.[29] Proteins are composed of amino acids, and a common concern with protein acquired from vegetable sources is an adequate intake of the essential amino acids, which cannot be synthesised by the human body. While dairy and egg products provide complete sources for lacto-ovo vegetarians, the only vegetable sources with significant amounts of all eight types of essential amino acids are lupin, soy, hempseed, chia seed, amaranth, buckwheat, and quinoa. However, the essential amino acids can also be obtained by eating a variety of complementary plant sources that, in combination, provide all eight essential amino acids (e.g. brown rice and beans, or hummus and whole wheat pita, though protein combining in the same meal is not necessary). A 1994 study found a varied intake of such sources can be adequate.[30]
Vitamin B12
Plants are not generally significant sources of vitamin B12.[35] However, lacto-ovo vegetarians can obtain B12 from dairy products and eggs, and vegans can obtain it from fortified foods and dietary supplements.[36][37] Since the human body preserves B12 and reuses it without destroying the substance, clinical evidence of B12 deficiency is uncommon.[38][39] The body can preserve stores of the vitamin for up to 30 years without needing its supplies to be replenished.[35]
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