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Health See also: Vegetarian nutrition [edit] Dietetic association positions
The American Dietetic Association annually publishes its position on vegan and vegetarian diets:
Appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes.[85]
In 2003, the Dietitians of Canada joined with the ADA to release a position paper to the same effect.[86] Similarly, the British Nutrition Foundation considers "well balanced" vegetarian diets to be nutritionally adequate,[87] and the Irish Nutrition and Dietetic Institute considers "well planned" vegetarian diets to be "nutritionally balanced for both adults and children".[88]
In contrast, both the Swiss Federal Nutrition Commission and the German Society for Nutrition recommend against a vegan diet, particularly for children, the pregnant and the elderly.[89][90] [edit] Nutritional benefits A vegan version of the nutritional food pyramid which normally includes meat and animal products. Click to enlarge.
Doctors Dean Ornish, T. Colin Campbell, John A. McDougall and Caldwell Esselstyn claim that high animal fat and protein diets, such as the standard American diet, are detrimental to health.[91][92] 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.[93][94][95][96]
According to the American Dietetic Association and Dietitians of Canada, diets that avoid meat tend to have lower levels of saturated fat, cholesterol, and animal protein, and higher levels of carbohydrates, fiber, magnesium, potassium, folate, and antioxidants, such as vitamins C and E, and phytochemicals.[6] People who avoid meat are reported to have lower body mass index than those following the average Canadian diet; from this follows lower death rates from ischemic heart disease; lower blood cholesterol levels; lower blood pressure; and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer.[6]
A 1999 meta-study of five studies comparing vegetarian and non-vegetarian mortality rates in western countries found the mortality rate due to ischemic heart disease 26% lower among vegans compared to regular meat eaters, but 34% lower among ovolactovegetarians and among those who ate fish but no other meat. The lower rate of protection for vegans compared to lacto-ovo vegetarians is believed to be linked to higher levels of homocysteine, which is caused by insufficient vitamin B12, and it is believed that vegans who get sufficient B12 should show even lower risk of ischemic heart disease than lacto-ovo vegetarians. No significant difference in mortality was found from other causes. The mortality rates over all were 0.82 for fish eaters,[verification needed] 0.84 for some omnivores and vegetarians, and 1.00 for vegans and omnivores.[97] A 2003 review of three studies comparing mortality rates among British vegetarians and non-vegetarians found only a nonsignificant reduction in mortality from ischemic heart disease, but noted that the findings were compatible with the significant reduction found in the 1999 review.[98]
A 2006 study found that in people with type 2 diabetes a low-fat vegan diet reduced weight, total cholesterol, and LDL cholesterol and did so to a greater extent than the diet prescribed by the American Diabetes Association.[99] [edit] Mental health benefits
A 2010 study compared a group of vegetarian and meat-eating Seventh Day Adventists, the two subgroups having relatively consistent lifestyle characteristics in other areas, in which vegetarians scored lower on depression tests and had better mood profiles.[100] [edit] Nutritional concerns Various fruits, vegetables, nuts, and grains; some basic ingredients of a vegan diet. [edit] Specific nutrients
The American Dietetic Association considers "appropriately planned" vegan diets "nutritionally adequate",[6] but poorly planned vegan diets can be deficient in nutrients such as vitamin B12,[101], iron,[102][103] vitamin D,[104] calcium,[104][105] iodine[106] and omega-3 fatty acids.[107] These deficiencies have potentially serious consequences, including anemia,[108] rickets[109] and cretinism[110] in children, and osteomalacia[109] and hypothyroidism[110] in adults. [edit] Vitamin B12
Deficiencies in Vitamin B12, a bacterial product that cannot be reliably found in plant foods,[108][111][112] can have serious health consequences, including megaloblastic anemia and neurodegenerative disease (including subacute combined degeneration of the cord).[113] Although clinical B12 deficiency is rare in vegans,[108] if a person has not eaten more than the daily needed amount of B12 over a long period before becoming a vegan then they may not have built up any significant store of the vitamin.[114] In a 2002 laboratory study, more of the strict vegan participants' B12 and iron levels were compromised than those of lacto- or lacto-ovo-vegetarian participants.[115]
The Vegan Society and Vegan Outreach, among others, recommend that vegans either consistently eat foods fortified with B12 or take a B12 supplement.[116][117][118] Tempeh, seaweed, spirulina, organic produce, soil on unwashed vegetables, and intestinal bacteria have not been shown to be reliable sources of B12 for the dietary needs of vegans.[108][119][120] [edit] Iron
Iron deficiency may lead to iron deficiency anaemia. Iron is less well absorbed from vegetarian diets (approximately ten percent absorption from vegetarian diets, versus approximately 18 percent absorption from an omnivorous diet); vegetarians who exclude all animal products may need almost twice as much dietary iron each day than non-vegetarians. On the other hand, the iron status of omnivores and vegans appears to be similar, and body absorption processes may adjust to low intakes over time by enhancing absorption efficiency.[121] Molasses is a high-iron food source and many vegans take it in spoonfuls as an iron supplement.[102][122] [edit] Calcium, vitamin D
It is recommended that vegans eat three servings per day of a high calcium food, such as fortified soy milk, almonds, hazelnuts, and take a calcium supplement as necessary.[6][104] The EPIC-Oxford study showed that vegans have an increased risk of bone fractures over both meat eaters and vegetarians, likely due to lower dietary calcium intake, but that vegans consuming more than the UK's estimated average requirements for calcium of 525 mg/day had risk of bone fractures similar to other groups.[105][123] A study of bone density found that vegans have bones 6% less dense than omnivores but that this difference was "clinically insignificant".[124] Another study by the same researchers examined over 100 vegan post-menopausal women and found that “…although vegans have much lower intakes of dietary calcium and protein than omnivores, veganism does not have (an) adverse effect on bone mineral density (BMD) and does not alter body composition.”[125]
The authors of The China Study argue that osteoporosis is linked to the consumption of animal protein because animal protein, unlike plant protein, increases the acidity of blood and tissues which is then neutralized by calcium pulled from the bones.[126] The authors add that "in our rural China Study, where the animal to plant ratio [for protein] was about 10%, the fracture rate is only one-fifth that of the U.S.," where consumption of animal products including dairy, is higher.[127]
For light-skinned people, adequate amounts of vitamin D may also be obtained by spending 15 to 30 minutes in the sunlight every few days. Dark-skinned people need significantly more sunlight to obtain the same amount of vitamin D, and sunlight exposure may be difficult for vegans in areas with low levels of sunlight during winter; in these cases supplementation is recommended.[109][111][128] [edit] Iodine
Iodine supplementation may be necessary for vegans in countries where salt is not typically iodized, where it is iodized at low levels, or where, as in Britain or Ireland, animal products are used for iodine delivery.[106][116] Iodine can be obtained from most vegan multivitamins or from regular consumption of seaweeds, such as kelp.[106][116] [edit] Choline
Vegans may be at risk of choline deficiency and may benefit from choline supplements.[129] Choline has many functions in the body, and choline deficiency may cause a number of health concerns.[130] The Institute of Medicine has set the Adequate Intake of choline at 425 mg (milligrams) per day for women and 550 mg/day for men[131][132], though dietary intake requirements for choline are not yet fully understood.[132][133] [edit] Pregnancies and children
The American Dietetic Association considers well-planned vegan diets "appropriate for all stages of the life cycle, including pregnancy and lactation,"[6] but recommends that vegan mothers supplement for iron, vitamin D, and vitamin B12.[134][135] Vitamin B12 deficiency in lactating vegetarian mothers has been linked to deficiencies and neurological disorders in their children.[136][137] Some research suggests that the essential omega-3 fatty acid α-linolenic acid and its derivatives should also be supplemented in pregnant and lactating vegan mothers, since they are very low in most vegan diets, and the metabolically related docosahexaenoic acid (DHA) is essential to the developing visual system.[138] Pregnant vegans may need to supplement choline (see section on choline, above). A maternal vegan diet has also been associated with low birth weight,[139] and a five times lower likelihood of having twins than those who eat animal products.[140]
Several cases of severe infant or child malnutrition and some infant fatalities have been associated with poorly planned, restrictive vegan diets, often insufficient in calories[141][142][143][144][145]. These incidents have provoked some to criticize vegan diets for children.[146][147] Parents involved in these cases were convicted on charges ranging from assault to murder. Dr. Amy Lanou, an expert witness for the prosecution in one of the cases, asserted that the child in that particular case "was not killed by a vegan diet" but that "the real problem was that he was not given enough food of any sort."[148] [edit] Eating disorders
The American Dietetic Association indicates that vegetarian diets may be more common among adolescents with eating disorders, but that the evidence suggests that the adoption of a vegetarian diet does not lead to eating disorders, rather that "vegetarian diets may be selected to camouflage an existing eating disorder."[6] Other studies and statements by dietitians and counselors support this conclusion.[149][150][151]
