There are several distinctive subgroups of vegetarians:
Vegetarianism is a lifestyle that has emerged in various civilizations around the world at various points in history out of different sets of motives. Archaeological findings indicate that prehistoric humans were not vegetarians but obtained about a third of their daily calories from meat or other animal products. The structure of the human digestive tract suggests that humans evolved as omnivores (animals that feed on both plant and animal substances), as human intestines are relatively short in comparison with the lengthy intestines found in herbivores (plant-eating animals). Like the stomachs of other carnivores (meat-eating animals) and omnivores, the human stomach secretes pepsin, an enzyme necessary for digesting the meat proteins rather than plant matter. The human mouth contains pointed teeth (canines and incisors) adapted for tearing meat as well as teeth with flat crowns (molars) for chewing plants. In addition to the anatomical evidence, anthropologists have not discovered any primitive societies in the past or present whose members maintained good health and consumed a purely vegetarian diet. All contemporary indigenous groups that are healthy include fish or dairy products in their diet, and most eat meat, even if only in small amounts or on rare occasions.
Religious belief is the oldest historical motive for vegetarianism. Hinduism is the earliest of the world's major religions known to have encouraged a vegetarian lifestyle. As of the early 2000s, Hinduism accounts for more of the world's practicing vegetarians (70%) than any other faith or political conviction. Different Hindus, however, explain their commitment to vegetarianism in different ways. Some associate vegetarianism with the doctrine of ahimsa, or nonviolence, which forbids the shedding of animal as well as human blood. Others believe that animals have souls, and that those who kill them will acquire bad karma and suffer in their next reincarnation. Lastly, some Hindus believe that their gods will not accept nonvegetarian offerings.
In ancient Greece, the followers of the philosopher and mathematician Pythagoras (c. 582–507 BCE) practiced an ascetic lifestyle that included a vegetarian diet and abstained from animal bloodshed, including sacrifices to the Greek gods. Neoplatonist philosophers of the third and fourth centuries CE revived the Pythagorean notion that vegetarianism helps to purify the soul. Because a plant-based diet was associated with Pythagoras, European Christians in the sixteenth and seventeenth centuries who practiced vegetarianism were often called Pythagoreans.
Mainstream Christianity in both its Eastern and Western forms has never made year-round vegetarianism mandatory for laypeople; however, there is a long tradition of monastic vegetarianism going back at least as far as the Desert Fathers in the third and fourth centuries CE. In addition, many Christians abstain from meat during certain seasons of the church year (Lent and Advent). One reason for vegetarian diets in some of the monastic orders is the belief that eating meat increases temptations to anger and violence. Another reason, found more commonly among evangelical Protestants, is the interpretation of Genesis 1:29 and other Bible passages as meaning that God originally intended humans to be vegetarians, and that God wants his present-day followers to be responsible stewards of the earth. The Christian Vegetarian Association (CVA), which welcomes Roman Catholics as well as mainstream and evangelical Protestants, was founded in 1999 and has produced several books, study guides, and a documentary film.
One Christian denomination that was formed in the United States in the nineteenth century, namely the Seventh-Day Adventist Church, has expected its members to be vegetarians since its beginning. Members of the church have been studied by the National Institutes of Health (NIH) and the National Cancer Institute (NCI) since 1960. NIH findings indicate that Adventist men live on average seven years longer than men in the general population, and Adventist women eight years longer than their non-Adventist counterparts.
Many members of New Age groups, as well as some atheists and agnostics, practice vegetarian or vegan lifestyles out of respect for nature or for the earth, even though they would not consider themselves religious in the conventional sense.
The application of scientific methods to agriculture in the eighteenth and nineteenth centuries also allowed people to calculate for the first time the cost to the environment of raising animals for meat. As early as the 1770s, the English clergyman William Paley had already urged a vegetarian lifestyle on the grounds that an acre of land used to raise fruits and vegetables could support twice the number of people as an acre used to graze animals. A common ethical argument for vegetarianism in the early 21st century is that 40% of the world's grain goes to feed animals raised for meat rather than to feed people and that world hunger could be eliminated if even half this grain could be redistributed to undernourished populations. According to the North American Vegetarian Society (NAVS), 15 vegans can be fed on the same amount of land needed to feed one person consuming a meat-based diet.
Commitment to a vegetarian diet as a way to reduce the suffering of animals, sometimes called compassion-based vegetarianism, emerged during the mid-19th century, a period that also witnessed the foundation of the first groups devoted to animal welfare. The Royal Society for the Prevention of Cruelty to Animals (RSPCA) was given its charter by Queen Victoria in 1840, seven years before the organization of the Vegetarian Society. The American Society for the Prevention of Cruelty to Animals (ASPCA) was founded in New York City by Henry Bergh in 1866. In addition to ongoing concern about maltreatment of household pets and working animals, the advent of factory farming has intensified the revulsion many people feel regarding the use of animals for human dietary consumption and clothing.
The minimum number of servings per food group in this diet would provide about 1,000 calories per day. Nonsedentary adults can meet higher energy needs by choosing more servings from any of the basic five groups. Sweets and alcohol should be used only sparingly.
Dietary supplements are recommended for vegetarians over 50 and for vegans, based on studies conducted by the National Academy of Medicine (formerly the Institute of Medicine or IOM).
Vegetarian diets can accommodate a wide variety of regional and ethnic cuisines as well as different philosophical or religious approaches. The following are only a few of the possible choices:
MEDITERRANEAN DIET. In its origin, the Mediterranean diet was not a purely vegetarian diet. It is, however, sparing in its use of red meat and eggs, and low in its use of fish and poultry. It can thus be easily adapted to a vegetarian or pesce/pollo vegetarian diet. The Mediterranean diet is high in its use of whole grains, fruits, nuts, and high-fiber vegetables; it appeals to many people because of its wide choice of flavorful foods.
MACROBIOTIC DIET. The macrobiotic diet, which was brought to Europe and North America from Japan in the 1960s, is associated with the Eastern concepts of yin and yang as well as with the elimination of animal products from the diet. This diet also involves such changes in eating habits as chewing each mouthful of food at least 50 times, drinking liquids only when thirsty, avoiding the use of aluminum cookware, and cooking foods on a wood stove rather than using electrical appliances.
ORNISH DIET. Developed by a medical doctor to reverse the signs of heart disease, the Ornish diet has also been popularized as a weight-loss program. It is a strict low-fat, high-fiber diet that excludes red meat, poultry, and fish, although people following this diet may use limited amounts of egg whites, fat-free milk, and other fat-free dairy products.
SEVENTH-DAY ADVENTIST DIET. Seventh-Day Adventists (SDAs) have followed vegetarian dietary regimens since the denomination was first organized in 1863. The diet recommended by the church's General Conference Nutrition Council (GCNC) in the early 2000s is an ovolactovegetarian diet, high in whole-grain breads and pastas and fresh vegetables and fruits, with moderate use of nuts, seeds, and low-fat dairy products and limited use of eggs. Some SDAs prefer a vegan diet. The church has its own professional organization for dietitians, which is affiliated with the AND, and encourages all its members to follow the AND guidelines for vegetarians.
The Vegetarian Resource Group offers the following suggestions for people considering vegetarianism:
Another suggestion for beginners offered by flexitarians is to ease into a vegetarian diet rather than beginning it abruptly: cut back gradually on the amount of meat, poultry, or fish in the diet until one is eating meat as part of the main meal no more than once or twice a week.
The long-term NIH study of Seventh-Day Adventists began to report in the 1970s and 1980s that lowered blood pressure, lower rates of cardiovascular disease and stroke, lower blood cholesterol levels, and lowered risks of colon and prostate cancer were associated with a vegetarian diet. In particular, SDAs were only half as likely to develop type 2 diabetes as were nonvegetarian Caucasians. Although it is possible to gain weight on a vegetarian diet, most people lose weight, especially in the first few months; and most vegetarians have lower body mass indices (BMI), an important diagnostic criterion of obesity, than their meat-eating counterparts.
Vegetarian diets may be effective in lowering the risk of rheumatoid arthritis, osteoporosis, kidney disease, gallstones, diverticulitis, and dementia as well as heart attacks, stroke, and diabetes, although one group of Canadian researchers maintains that these diets do not in fact lower the risk of chronic degenerative diseases. Vegetarian diets have, however, been shown to be useful in treating constipation in adults and children as well as dysmenorrhea (painful menstrual periods) in women of childbearing age.
The AND strongly recommends that people consult a registered dietitian as well as their primary physician before starting a vegetarian diet. The reason for this precaution is the variety of vegetarian regimens as well as the variations in height, weight, age, genetic inheritance, food preferences, level of activity, geographic location, and preexisting health problems among people. A nutritionist can also help design a diet that a new vegetarian will enjoy eating and that will ensure that he or she is getting adequate nourishment and other health benefits.
The Academy also notes in particular that dietary choices for athletes depend on whether the athlete is consuming a lactovegetarian, ovolactovegetarian, or vegan diet: “Athletes need to eat small amounts of protein throughout the day to ensure this important nutrient is available when their bodies need it most… not every source of protein is equal…Meat, eggs and dairy foods are typically the most coveted protein sources because they contain all nine essential amino acids in the ratios that humans require.”
Another area of concern is in veterinary medicine, namely, the trend among some pet owners to put dogs and cats on vegetarian diets, often with homemade foods. Cats in particular are at risk of malnutrition and eventual blindness on a vegetarian or vegan diet because they are obligate carnivores (must have meat in the diet). Their bodies cannot form taurine (an amino acid), thiamin, retinol (a form of vitamin A essential to healthy eye tissue), and vitamin B12, all micronutrients found primarily in meat. The Vegetarian Society (UK) has an information sheet warning against putting cats on a vegetarian diet, and the American Veterinary Medical Association (AVMA) strongly urges vegetarian pet owners to consult their veterinarian before offering either dogs or cats vegetarian pet food.
The longstanding concern about vegetarian diets is the risk of nutritional deficiencies, particularly for such important nutrients as protein, minerals (iron, calcium, and zinc), vitamins (vitamin D, riboflavin, vitamin B12, and vitamin A), iodine, and omega-3 fatty acids. The 2003 vegetarian food guide recommends that vegetarians over 50 years of age as well as vegans in all age groups take supplements of vitamin B12, and vitamin D, or use foods fortified with these nutrients. Pregnant women are another subgroup of vegetarians who should ensure that they are taking in enough vitamin B12,. Vitamin D supplements are particularly important for vegans living in northern latitudes or other situations in which they receive little sun exposure.
Strict macrobiotic diets carry the risk of nutritional deficiencies unless they are very carefully planned. Many forms of the macrobiotic diet are deficient in vitamin C and can lead to scurvy, a disease of the gums, teeth, and skin. Children are at increased risk of nutritional deficiencies on these diets. In addition, macrobiotic diets have not been tested in pregnant or lactating women, and extreme versions of the macrobiotic diet may not provide enough calories for normal fetal growth.
The AND has a professional subgroup called the Vegetarian Nutrition Dietary Practice Group, or DPG, which publishes a quarterly newsletter called Vegetarian Nutrition Update. The newsletter is available to nonmembers of the AND for an annual subscription fee. The Vegetarian Nutrition DPG also has its own web page at http://www.eatrightpro.org/resource/membership/academy-groups/dietetic-practicegroups/vegetarian-nutrition-dpg .
Once considered an eccentricity, vegetarianism is widely accepted by the general public in developed countries as a legitimate dietary option in the early 2000s. Most restaurants, school cafeterias, airlines, and other public food services offer vegetarian dishes as a matter of course. The AND notes in its 2016 position paper that vegetarians now have increased technological support: “applications for mobile devices allow vegetarians to discover nutritional needs, track intake, and locate restaurants and markets.” The Vegetarian Resource Group (VRG), a nonprofit research organization, conducted a poll in 2016 that indicated that about 8 million adults in the United States are vegetarian; about 3.4 million of these are vegans. As of 2018, the Northeast has the highest percentage of adults who are vegetarians or vegans (5.4%), with the lowest percentages (2.3%) in the South and Midwest. About 3% of Hispanics and 3% of African Americans are vegetarians or vegans.
Most opposition to vegetarianism in developed countries is interpersonal rather than scientific or political, as some vegetarians are perceived as developing a sense of moral or spiritual superiority to nonvegetarians and may make themselves socially unpopular by criticizing or lecturing others for continuing to eat meat. NAVS advises new vegetarians, “Be cheerful about your new adventure [but] remember to let people come to their own dietary conclusions.”
Some evidence shows, however, that many people find vegetarian and vegan diets difficult to maintain over the long term. A research group called Faunalytics reported in 2014 that about 10% of adult Americans are former vegetarians and vegans: “About 84% of vegetarians/vegans abandon their diet, and more than half of former vegetarians/vegans abandoned the diet within the first year, and a third of them abandoned it in three months or less.” The chief factor in giving up a vegan or vegetarian diet is living with a family member or roommate who eats meat.
As has been noted in Europe as well as the United States, the emphasis in medical research on vegetarian diets has shifted from concern about nutritional deficiencies in people following these diets to the role of vegetarianism in preventing or treating chronic diseases. It was the NIH's studies of Seventh-Day Adventists that first indicated that vegetarian diets can lower the risk of heart disease, stroke, and type 2 diabetes. The Adventist Health Study received new funding in 2003 for its continuation. The Adventist Health Study-2 (AHS-2), an ongoing study of 96,000 SDAs in the United States and Canada carried out by the Loma Linda University School of Public Health, maintains a website with early findings about the benefits of the Adventist diet.
Research done after 2010 indicates that people in the developed countries choose vegetarian diets for reasons other than weight loss. A study of data from the 2012 National Health Interview Survey reported in 2017 that women are more likely than men to follow vegetarian diets “for unspecific health reasons,” usually described as illness prevention or general wellness. The vegetarians also were more likely to be single, college-educated, and using herbal products and vitamin supplements as part of their diet.
See also Academy of Nutrition and Dietetics ; Calcium ; Calories ; Constipation ; Detoxification diets ; Dietary supplements ; Flexitarian ; Fruitarian diet ; Gallstones ; High-fiber diet ; Iodine ; Iron ; Lacto-vegetarianism ; Macrobiotic diet ; Malnutrition ; Mediterranean diet ; Minerals ; Obesity ; Ovolactovegetarianism ; Phytonutrients ; Protein ; Riboflavin ; Sports nutrition ; Veganism ; Vitamin A ; Vitamin B12 ; Vitamin D ; Vitamins ; Whole grains ; Zinc .
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Academy of Nutrition and Dietetics, 120 S. Riverside Plaza, Ste. 2190, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, firstname.lastname@example.org, http://www.eatright.org .
American Vegan Society (AVS), 56 Dinshah Lane, PO Box 369, Malaga, NJ, 08328, (856) 694-2887, Fax: (856) 694-2288, http://www.americanvegan.org .
National Center for Complementary and Integrative Health (NCCIH), 9000 Rockville Pike, NIH Campus, Bldg. 31, Bethesda, MD, 20892, (888) 644-3615, https://nccih.nih.gov/tools/emailnccih , https://nccih.nih.gov .
Vegetarian Resource Group (VRG), P.O Box 1463, Baltimore, MD, 21203, (410) 366-8343, email@example.com, http://www.vrg.org .
Rebecca J. Frey, PhD