The Vegan Diet
Veganism (also known as strict vegetarianism or pure vegetarianism) is a philosophy and lifestyle that avoids using animals and animal products for food, clothing and other purposes. In practice, a vegan (an adherent of veganism) commits to the abstention from consumption or use of all animal products, including meat, fish, poultry, honey, eggs and dairy products, as well as articles made of fur, wool, bone, leather, feathers, pearls, nacre, coral, sponges and other materials of animal origin. Many vegans also avoid products that have been tested on animals.
People become vegans for a variety of reasons, including ethical concerns such as animal rights and the environment, as well as more personal reasons such as health benefits and spiritual or religious concerns. A Time/CNN poll published in Time on July 7, 2002, found that 4% of American adults consider themselves vegetarians, and 5% of self-described vegetarians consider themselves vegans. This suggests that 0.2% of American adults are vegans. In 2002, the UK Food Standards Agency reported that 5% of respondants self-identified as vegetarian or vegan. Of that 5%, approximately 10% ate white meat, nearly half ate fish and 95% ate dairy. Based on these figures, approximately 0.25% or less of the UK population follow a vegan diet. The Times estimates there are 250,000 vegans in Britain.
More About Veganism:
The British Vegan Society defines veganism as:
A philosophy and way of living which seeks to exclude — as far as is possible and practical — all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose; and by extension, promotes the development and use of animal-free alternatives for the benefit of humans, animals and the environment. [In dietary terms the society defines Veganism as] The practice of dispensing with all products derived wholly or partly from animals.
—Vegan Society
The American Vegan Society uses a similar definition:
Vegans exclude flesh, fish, fowl, dairy products (animal milk, butter, cheese, yogurt, etc.), eggs, honey, animal gelatin, and all other foods of animal origin. Veganism also excludes animal products such as leather, wool, fur, and silk in clothing, upholstery, etc. Vegans usually make efforts to avoid the less-than-obvious animal oils, secretions, etc., in many products such as soaps, cosmetics, toiletries, household goods and other common commodities.
—American Vegan Society
The term "animal product" in a vegan context refers to material derived from non-human animals for human use or consumption. Human breast milk, for example, is acceptable when voluntarily used for human babies, but, by comparison, when a human being drinks a cow's milk, it is regarded as the consumption of an "animal product". Products of human origin that are obtained involuntarily are not considered acceptable.
Animal products include meat, poultry, seafood, eggs, dairy products, fur, leather, wool, pearls, and nacre (mother of pearl). By-products include gelatin, lanolin, rennet, and whey. Items derived from insects include items such as silk, honey, beeswax, shellac and cochineal.
Some vegans avoid cane sugar that has been filtered with bone char and will not drink beer or wine clarified with albumen, animal blood, or isinglass, even though these are not present in the final product. Some also avoid food cooked in utensils that have been used to cook non-vegan foods. Vegans also avoid toothpaste with calcium extracted from animal bones if they are aware of it. Similarly for soap with ingredients which may have been extracted from animal fat (e.g. stearic acid).
Most vegans refrain from supporting industries that use animals directly or indirectly, such as circuses and zoos, and will not use products that are tested on animals.
Origin of the name
The word vegan, usually pronounced /ˈviːgən/, was originally derived from "vegetarian" in 1944 when Elsie Shrigley and Donald Watson, frustrated that the term "vegetarianism" had come to include the eating of dairy products, founded the UK Vegan Society. They combined the first three and last two letters of vegetarian to form "vegan", which they saw as "the beginning and end of vegetarian".
Since the founding of the UK Vegan Society, the term vegan has come to encompass people who seek to eliminate animal products in all areas of their lives, as opposed to those who simply avoid eating animal products. Although veganism as a secular movement is a 20th-century idea, abstaining from all animal products can be traced back to various religious ascetics (see Vegetarianism and religion).
Motivations
Ethics
Vegans generally oppose the violence and cruelty involved in the meat[6], dairy, non-vegan cosmetics, clothing, and other industries. (See draize test, LD50, animal testing, vivisection, and factory farming)
Some utilitarian philosophers, such as Jeremy Bentham and Peter Singer, argue that the suffering of sentient animals is relevant to ethical decisions, though they do not rely on the concept of rights and believe that non-human animals only have an interest in not suffering. Others like Gary L. Francione, believe that all sentient beings have an interest in both not suffering and continuing to live. A common argument is that animals have the ability to feel pleasure so killing them is wrong, because it destroys any hope of future pleasure. He claims that it is therefore unethical to treat them as property or a means to an end (see animal rights). Although these theories draw similar conclusions, they are not wholly compatible with one another.
Health
Vegans suggest that their diet is healthier than an omnivorous diet. They also argue that additional health benefits are gained by not consuming artificial substances such as growth hormones and antibiotics, which are often given to farmed animals.
The American Dietetic Association and Dietitians of Canada state that "well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence."
Vegan diets tend toward several nutritional benefits, including significantly lower levels of saturated fat, no cholesterol, and higher levels of carbohydrates, fiber, magnesium, potassium, folate, antioxidant vitamins C and E and phytochemicals.
Vegetarians have been reported to have lower body mass indices than nonvegetarians, although there was no significant difference in blood pressure rates. There is some evidence that vegetarians have lower rates of death from ischemic heart disease, and that non-meat eating reduces all-cause mortality by 50%. Research suggests that the vegan diet can reduce blood cholestorol in people with, and significantly reduce the complications of non-insulin dependent diabetes (NIDDM).
There are a growing number of vegan athletes. Vegan athletes compete in a variety of sports, such as powerlifting, bodybuilding, martial arts, long distance running, and many others. Multiple Olympic gold medallist Carl Lewis has stated that he was vegan at the peak of his career, when he became the first man to officially break 9.90 seconds in the 100 Metre sprint. (Ben Johnson broke 9.90 seconds in the 1988 Olympics but was disqualified for the use of performance enhancing drugs.)
Some studies have found benefits associated with diets rich in whole plant foods, and risks associated with diets rich in animal-based foods. One of the researchers from the 1990 epidemiological study, "The China Study", said "Even small increases in the consumption of animal-based foods was associated with increased disease risk,"Studies in Japan found that increased consumption of some animal products coincided with a decrease in risk for some forms of cerebrovascular disease and stroke mortality.
There are also claims that industry livestock feeding practices pose health threats to human consumers. According to Dr. Michael Greger in a January 2004 lecture at MIT (which was the basis for Whistleblower, a 2006 documentary film by Jeff Bellamar) each year more than one million tons of animal excrement are fed back to farm animals raised for human consumption to lower the feed costs. He also says that up to 10% of blood from killed animals is mixed into some cattle feed, and up to 30% of some poultry feed is made up of the blood. Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is believed to be caused by cows being fed with contaminated meat and bone meal, a high-protein substance obtained from the remnants of butchered animals, including cows and sheep. In most parts of the world, such remnants are no longer allowed in feed for ruminant animals, but the practice persists in a few countries.
Resources and the environment
Main article: Environmental vegetarianism
People who adopt a vegan diet to reduce resource consumption or ecological footprint extend the idea of environmental vegetarianism to all animal products. The fundamental rationale is that each additional trophic level in a food chain passes on only a fraction of the energy it consumes, so a diet that consists of plant products rather than animal products will generally use significantly less of all resources, and indirectly cause less environmental damage.
A study by Gidon Eshel and Pamela Martin, assistant professors of geophysics at the University of Chicago, compares the CO2 production resulting from various human diets. They find that a person switching from the typical American diet to a vegan diet would, on average, reduce CO2 production significantly more than switching to a hybrid vehicle. They go on to recommend a vegan diet for this reason, as well as the potentially adverse health effects of dietary animal fats and proteins. They go on to support their claims by referencing various studies linking animal fats to cardiovascular diseases and animal proteins to cancer (see pages 15-18 of the study).
Feminism
Some third-wave feminists such as Carol Adams reject the consumption of meat and analogize the use and objectification of animals to the use and objectification of women in society. This criticism focuses on societal construction of ties between women and the environment and references the fact that a large majority of livestock animals are female[citation needed].
Vegan cuisine
For recipes and further information see the Wikibooks Cookbook article on Vegan Cuisine.
The cuisines of most nations contain some dishes that are plant-based (and therefore suitable for a vegan diet) as are specific traditional ingredients, e.g. tofu, tempeh and the wheat product seitan in Asian diets. Also, according to Sturtivants Edible Plants of the World, there are 2,897 plants that may be used for food. Therefore, the variety of vegan food available is quite diverse.
Many vegans prefer to cook without reference to meat, instead preparing meals from largely unprocessed ingredients such as pulses, grains, vegetables, nuts and fruit. However, artificial "meat" products (often called "analogs" or "mock meats") made from non-animal derived ingredients such as soya or gluten, including imitation sausages, ground beef, burgers, and chicken nuggets are widely available. Many recipes that traditionally contain animal products can be adapted by substituting vegan ingredients, e.g. nut, grain or soy milk used to replace cow's milk; eggs replaced by substitutes such as products made from potato starch.
On the one hand, vegan cuisine is not new. In nations that culturally do not use a large proportion of dairy products such as China, Japan and Thailand it has a well developed tradition that is centuries old due mainly to the influence of Buddhism. Furthermore, in many South Asian countries (India, Pakistan, Sri Lanka, Nepal, Bhutan) Hinduism, Jainism, and non-religious cultural traditions have kept the consumption of meat considerably lower than in many Western countries. These religions and traditions, in concert with economic barriers that make eggs, milk, and dairy products luxury items, have produced many de facto vegans over the centuries. On the other hand, many vegans have adapted their diets to fit in with modern eating patterns.
Similar diets and lifestyles
There are several diets similar to veganism, though there are significant differences, including fruitarianism, the raw food diet, the macrobiotic diet and Natural Hygiene. There are also numerous religious groups that regularly or occasionally practice a similar diet, including Jainism, some sects of Buddhism, Hinduism, and some Christian churches, particularly the Seventh-day Adventist Church. Fasts in the Eastern Orthodox Church resemble a vegan diet, however believers are not expected to be vegan throughout the whole year.
More recently, many young people who are a part of the anarcho-punk or hardcore punk/straight edge movements have embraced veganism (notable bands being Earth Crisis and Path Of Resistance), and the corresponding beliefs of the animal rights movement. Straight edge is a philosophy that rejects the use of alcohol, unsafe sex, recreational drugs and in some individual cases, safe sex, originating as a reaction to what some perceived as the cultural excesses of the 1980s both within the mainsteam and the punk subculture.
A subset of veganism, raw veganism, advocates the consumption only of raw foods and the elimination of processed foods from the diet. A study of raw vegans found them to be slender and healthy, but noted that they had reduced essential bone mass and lower bone mineral density. The researchers said these results are "strongly associated with increased fracture risk" but noted that the raw vegans they studied had no other biological markers to indicate higher levels of osteoporosis, and that their bone turnover rates were normal.
Vegan nutrition
Main article: Vegan nutrition
Nutrition authorities say that a properly planned vegan diet presents no significant nutritional problems. Supplementation is highly recommended, although this applies to non-vegans, too — Drs. Fletcher and Fairfield concluded, in JAMA (Journal of the American Medical Association) in June 2002, that "[i]t appears prudent for all adults to take vitamin supplements."[22] Vegans are potentially at risk for being deficient in several nutrients, such as vitamin B12, iron and iodine. These deficiencies can have potentially serious consequences, including anemia, pernicious anemia, cretinism and hyperthyroidism.
Calcium
Calcium may also be a concern to vegans who are not eating a variety of foods, especially leafy green vegetables (such as spinach, kale, collard greens, cabbage, etc.), almonds, oats, soy products (soy milk, tofu, etc.), sesame seeds, most beans, and dried fruits, most of which should be included in any diet, vegan or not.
The USDA's study on calcium and osteoporosis in women began with the premise that animal proteins create sulphur in the body, which leaches out calcium from the bones. The results, though, were more complex: the vegan subjects lost bone density at the same rate as their vegetarian and non-vegetarian peers; when put on a weight-bearing exercise regimen, the vegan subjects built bone density at a significantly higher rate than the other subjects. The researchers remark, "If you have less bone formation, the result is the same as if you had an increase in bone resorption. So, even though bone resorption was the same in both groups of volunteers, the lower amount of bone formation in the omnivore women could lead to a decrease in their bone density."
[edit] DHA
One nutrient that is sometimes overlooked when analyzing the vegan diet is docosahexaenoic acid (DHA). For non-vegans, good sources for this omega-3 fatty acid include edible marine fish and shellfish and eggs. This healthy fat can also be found in Algae and vegan DHA dietry supplement capsules are now available. This fatty acid is very important for brain function, eye function, and for the cellular transport of valuable nutrients. "ALA" can be converted by the body into DHA. ALA is found in soybeans, walnuts, flaxseed, pumpkin seeds, and canola oil: many vegans include these specific foods in their diets. To obtain the same benefit, it has been estimated that 10x the amount of ALA as DHA must be consumed.
[edit] Iodine
Some information in this article or section has not been verified and may not be reliable.
Please check for any inaccuracies, and modify and cite sources as needed.
Residents of the UK may find themselves iodine-deficient if they rely on local produce, since in the UK iodine is usually obtained via dairy products rather than iodized salt that is more common elsewhere. The Vegan Society says, "Iodine is typically undesirably low (about 50 micrograms/day compared to a recommended level of about 150 micrograms per day) in UK vegan diets unless supplements, iodine rich seaweeds or foods containing such seaweeds are consumed. The low iodine levels in many plant foods reflects the low iodine levels in the UK soil, due in part to the recent ice-age." This demonstrates that location may also be a factor in what deficiencies may be present in any given diet.
[edit] Iron
Some information in this article or section has not been verified and may not be reliable.
Please check for any inaccuracies, and modify and cite sources as needed.
Iron is present in many typically vegan foodstuffs. These include grains, nuts and green leaves, although the iron in these sources is in a less easily absorbed, non-heme form. Nevertheless, the Vegan Society quotes research to show that iron deficiency is no more prevalent in vegans than in the general population. This research did not account for the fact that many vegans take nutritional supplements that are not found in food alone, whereas other research that excludes this subset of people does indeed show a marked iron deficiency among a majority of those studied.
Vitamin C facilitates the absorption of iron, and, indeed, can double or triple the amount of iron absorbed when taken with food. Vegans typically have high levels of vitamin C in their diets, which may account for the rarity of anaemia amongst them. However, diets lacking in heme-form iron can contribute to anemia and impair performance in endurance athletes (especially females, see menstrual cycle) due to their increased need for hemoglobin in the blood.
[edit] Protein
Frances Moore Lapp�'s 1971 bestseller Diet for a Small Planet popularized the claim that the protein in plant foods was incomplete and that vegetarians had to "combine" different plant foods (e.g., beans and grains) in order to get a "complete" protein. A decade later in The McDougall Plan (1983) Dr. John McDougall responded that this idea is incorrect and that common plant foods actually contain complete proteins. In The McDougall Program (1990) he wrote, "Nature designed and synthesized our foods complete with all the essential nutrients for human life long before they reach the dinner table. All the essential and nonessential amino acids are represented in single unrefined starches such as rice, corn, wheat, and potatoes in amounts in excess of every individual's needs, even if they are endurance athletes or weight lifters." The World Health Organization standard for protein intake is cited in support of this interpretation. Lapp� herself renounced the idea that protein combining was necessary in the 10th edition of Diet for a Small Planet, stating:
With three important exceptions, there is little danger of protein deficiency in a plant food diet. The exceptions are diets very heavily dependent on fruit or on some tubers, such as sweet potatoes or cassava, or on junk food (refined flours, sugars, and fat). Fortunately, relatively few people in the world try to survive on diets in which these foods are virtually the sole source of calories. In all other diets, if people are getting enough calories, they are virtually certain of getting enough protein."
Vitamin B12
Vitamin B12, a bacterial product, cannot be reliably found in plant foods, and so vegans are recommended to eat foods with B12 added (such as fortified soy milk, fortified margarines, or many commercial breakfast cereals), certain brands of nutritional yeast, or take dietary supplements (a good multivitamin will likely include B12 in sufficient quantities). Tempeh and some other fermented foods contain B12, although they cannot be considered reliable sources. Some plants (notably seaweeds) and fungi (mushrooms) absorb trace amounts of B12 from growing in bacteria-rich environments. B12 is also naturally synthesized in the colon of the human body and the intestines of other animals. Inadequate absorption of the body's stores of vitamin B12 poses a health risk, so the vitamin must often be ingested through fortified products and nutritional yeast. Older people - vegan and non-vegan alike - may experience difficulties in absorbing B12 from their food, and anemia (caused by B12 deficiency) is not unknown amongst omnivores. B12 deficiency has symptoms such as loss of appetite, fatigue, weakness, dizziness and confusion and can lead to irreversible neurological damage. It is particularly problematic for pregnant women and fetal development, as well as for infants who are breast-fed by a deficient mother.
Vitamin D
Vitamin D (vitamin D2) only occurs naturally in some mushrooms (eg. shiitake) and fungi. It is also available in fortified foods and can be produced in the body from sunlight shining on the skin.
Vitamin D3 only occurs naturally in animal-derived foods, however, like other D-vitamins, it is naturally produced in the skin in response to sunlight, so it is not necessary to ingest it.
Cultural aspects
Veganism has been slowly gaining greater popularity amongst some African Americans since the 1960s because of the involvement of politically-oriented African-American activists, actors and musicians[23]; a whole foods, mostly unprocessed diet is positioned as a return to ancestral African diets, an inexpensive and healthy alternative to current dietary habits, and a tool for African-American empowerment in the face of socio-economic disadvantage, especially health. Coretta Scott King, activist and wife of assassinated civil rights leader Martin Luther King, Jr. became vegan in 1995 as an extension of her belief in nonviolence. Her son, Dexter Scott King, had been vegan since 1988, saying that an appreciation for animal rights is the "logical extension" of his father's philosophy of nonviolence.
Product certification
The not-for-profit U.S. organization Vegan Action administers a certification programme in which manufacturers of vegan food products can have their products certified as vegan, and carry a related logo.
Criticism and controversy
Difficulty
The perceived difficulty of following a vegan diet prevents some people from believing it to be worthwhile. In particular, some find the label-checking, substituting for non-vegan ingredients, or taste differences necessary for a vegan diet burdensome or impractical, especially in many western cultures. When avoiding animal products is particularly impractical, some vegans invoke the "as far as is possible and practical" clause of the diet's definition.
In shopping, veganism requires checking the labels on all packaged foods, since many products have an animal product as a minor ingredient. Partially easing the burden, some labels explicitly state whether the food contains animal products. Several ingredients that occur in packaged goods, such as casein, are not recognized as non-vegan by most people, adding another difficulty for new vegans.
In cooking, ingredient substitution or avoidance becomes necessary for many dishes, especially in western diets that often use dairy products. Certain vegan substitutions for non-vegan ingredients (such as some egg replacers) do not perfectly mimic their animal-based originals and may not work well in recipes designed for the animal-based ingredients. Such substitutions can affect the recipe results—altering such aspects as flavour, texture and appearance. Some vegans find it more effective to use recipes designed to be vegan counterparts of non-vegan dishes than to simply subsitute individual ingredients into non-vegan recipes.
Many health supplements such as vitamins, minerals, and herbal alternatives are placed inside capsules made of animal-based gelatin. Though online retailers have emerged selling vegan alternatives to such products, and vegan-friendly multivitamins and supplements can now be found in most health food stores, it is legally available only in the developed world.
A majority of medications and dietary supplements contain a number of ingredients that are derived from animal sources such as magnesium stearate, stearic acid (used in soaps), gelatin, lactose, and many more. When the medicine itself is derived from an animal source there may not be an acceptable substitute, especially in life saving drugs like antivenom. All Food and Drug Administration approved drugs sold in the United States are animal tested, as animal testing is a requirement for drug approval for U.S. markets. Additionally, in some hospitals, Catgut in sutures and non-vegan latex gloves are used. Bandages contain Chitosan, a chemical derived from crustaceans. This chemical is also used in the water filtration process among other uses. Many vegans allow small amounts of animal products in medicine, believing that its use does not conflict with the definition or spirit of veganism due to the lack of substitutes.
In addition to foods and medicines, many household products like cosmetics, toiletries, household cleaners, pesticides, and cement contain either animal ingredients or ingredients that have been tested on animals, as well as animal-sourced coloring agents like Cochineal. Products such as leather, felt, cashmere, angora, certain waxes, and silk derive from animal products or by-products. Some fruits (for example apples are treated with shellac or carnauba) are treated with artificial or natural wax derived from oil or animal by-produce (shellac comes from an insect).
[edit] Ethical criticism
Many vegans question whether it is ethical to make use of products which result in the death of animals. Organizations such as the Foundation for Animal Use Education dispute that a non-vegan diet entails exploitation of or cruelty to animals, and support the concept of animal welfare while promoting the use of animals in food and fiber agriculture. These groups also dispute whether animals are sentient and have inherent rights, stating that rights are a function of being "moral agents" making moral judgments and comprehending moral duty, and that animals do not exercise responsibility as moral agents.
Some scientists dispute the assumption that a vegan lifestyle prevents unnecessary death of animals. Steven Davis, professor of animal science at Oregon State University, claims that the number of wild animals killed in crop production is greater than those killed in ruminant-pasture production. Gaverick Matheny wrote a rebuttal in which he claims that Davis' reasoning contains several major flaws, including the notion that vegans generally eat at a lower trophic level.
According to one scientist of the US Agricultural Research Service, it is "unethical" to put children on a vegan diet in some cases since it could harm their development. Later, the same scientist added that "vegan diets were unethical unless those who practiced them were well-informed about how to add back the missing nutrients through supplements or fortified foods."
Health criticism
The American Dietetic Association says that a well-planned vegan diet is appropriate in all stages of life but "individual assessment of dietary intakes of vegetarians is required."Other nutritionists have expressed concerns about the potential dangers in the vegan diet. This, in some cases involving severe nutritional inadequacy in conjunction with a strict vegetarian diet, may be particularly relevant to young children where the failure to achieve adequate nutrition can lead to permanent developmental deficits. In reported comments, Professor Lindsay Allen of the United States Agricultural Research Service declared: "There's absolutely no question that it's unethical for parents to bring up their children as strict vegans, unless those who practiced them were well-informed about how to add back the missing nutrients through supplements or fortified foods."[27][28] Vegans should be particularly concerned with adequate intake of vitamins like Vitamin A and Vitamin B12. Vegans are at a higher risk of vitamin A deficiency because in its true form (also called retinol) it is found only in animal foods such as fish oils and liver. This form is readily absorbed by the body. Plants do not contain vitamin A, but rather provitamin A and despite consumption of such provitamin A rich foods there might be vitamin deficiencies because of the consumption of insufficient amount of fat together with carotene-rich vegetables, and dietary deficiencies in iron and zinc. Vitamin B12, a bacterial product, cannot be reliably found in plant foods.
In a recent laboratory study, 60% of the strict vegan participants had a vitamin B12 deficiency, as compared with the lacto- or lacto-ovo-vegetarian participants (who were able to acquire vitamin B12 from these animal sources). In addition, lower counts of lymphocytes (the white blood cells responsible for immune system responses) and platelets (responsible for blood coagulation) and alterations in the iron metabolism and transport, were demonstrated. Another study published by the same group of researchers has shown that 45% of the vegetarian participants had higher homocysteine levels, a factor which has been strongly implicated in cardiovascular disease. This, in turn, may alter DNA methylation patterns, which has been associated with aging, cancer, atherosclerosis and other diseases. According to these authors, "three observations indicate that DNA methylation could be diminished by a vegetarian lifestyle. The vegetarian diet has a low content of methionine, remethylation of homocysteine is reduced by vitamin B12 deficiency and elevated homocysteine levels can induce the generation of S-adenosylhomocysteine (SAH), a potent inhibitor of methyltransferases."
Professor Allen also conducted research in rural Africa, partially backed by the U.S. based National Cattlemen's Beef Association, in which she demonstrated a dramatic improvement in the health of individuals who had, prior to the study, been on diets completely lacking in animal products. The study concluded that the added nutrients, especially vitamin B12 contained in the meat and milk improved the health of the children in the study. However, the British Dietetic Association stated that the findings were not applicable to vegan children in the developed world. They note that B12, reliably found only in animal products, is now included in many fortified foods generally available. Noting that the impoverished children in the study had diets deficient in zinc, B12 and iron, they concluded, "There is no evidence that our vegan and vegetarian children in this country suffer impaired development". They did note, however, that young children, pregnant and nursing women are vulnerable as vegans, urging parents to review their children's diets to be sure that they have a well-balanced diet.
Although the human body stores vitamin B12, a few months after adopting a strict vegan diet are enough to deplete them. Vegan people then become vulnerable to several common food and drug interactions which usually do not affect non-vegetarians, but that lower significantly the already low level of vitamin B12 in their bodies. Medical signs and symptoms caused by this are usually very hard to diagnose and to correlate to the vegan diet. For example, anesthesia with nitrous oxide may cause a dangerous fall in vitamin B12 levels, as well as smoking (nicotine), drinking (ethanol), antibiotics, cimetidine, cholestyramine, and other substances. People with diabetes who are being treated with metformin, and HIV-positive people being treated with zidovudine (AZT) should not follow vegan diets without B12 supplementation, as these substances are known to strongly reduce absortion and/or B12 levels.
Vegan mothers who do not obtain adequate vitamin B12 in their diet while breastfeeding can cause severe and permanent neurological damage to their infants.
Related studies note the importance of early recognition of significant maternal vitamin B12 deficiency during pregnancy and lactation in vegetarians is emphasized so that appropriate supplementation can be given and irreversible neurologic damage in the infant prevented. Critics also point to studies which show that a Vegetarian diet is linked to genital defects. They also cite that a vegan diet carries an increased risk of hemorrhagic stroke.
A study by the University of Minnesota school of health found that adolescent vegetarians are at greater risk than others for involvement in unhealthy and extreme weight control behaviors. Vegetarian males are at particularly high risk. Vegan dietician Brenda Davis claims current research indicates as many as 50% of people with anorexia nervosa or bulimia nervosa self-proclaim a vegetarian diet as a cover for their avoidance of eating "meat" or other "high fat foods". Also, Vesanto Melina, a B.C. registered dietitian and author of Becoming Vegetarian, stresses there is no cause and effect relationship between vegetarianism and eating disorders although people who have eating disorders may label themselves as vegetarians "so that they won't have to eat."A 1987 review of 116 cases found that 63 (54.3%) avoided red meat but that only 4 (6.3%) had avoided red meat prior to the onset of anorexia nervosa. The American Dietetic Association found that vegetarian diets may be more common among adolescents with eating disorders than in the general adolescent population, and that professionals should be aware of adolescents who limit food choices and exhibit symptoms of eating disorders. The ADA indicates that the evidence suggests that the adoption of a vegetarian diet does not lead to eating disorders, but "vegetarian diets may be selected to camouflage an existing eating disorder".