Vegetarianism



Vegetarianism is the practice of abstaining from the consumption of meat – red meat, poultry, seafood and the flesh of any other animal; it may also include abstention from by-products of animal slaughter.

Vegetarianism can be adopted for different reasons. Many object to eating meat out of respect for sentient life. Such ethical motivations have been codified under various religious beliefs, along with the concept of animal rights. Other motivations for vegetarianism are health-related, political, environmental, cultural, aesthetic or economic. There are varieties of the diet as well: an ovo-vegetarian diet includes eggs but not dairy products, a lacto-vegetarian diet includes dairy products but not eggs, and an ovo-lacto vegetarian diet includes both eggs and dairy products. A vegan, or strict vegetarian, diet excludes all animal products, including eggs, dairy, beeswax and honey. Some vegans also avoid animal products such as leather for clothing and goose-fat for shoe polish.

Various packaged or processed foods, including cake, cookies, candies, chocolate, yogurt and marshmallows, often contain unfamiliar animal ingredients, and may be a special concern for vegetarians due to the likelihood of such additions. Often, products are reviewed by vegetarians for animal-derived ingredients prior to purchase or consumption. Vegetarians vary in their feelings regarding these ingredients, however. For example, while some vegetarians may be unaware of animal-derived rennet's role in the usual production of cheese and may therefore unknowingly consume the product, other vegetarians may not take issue with its consumption.

Semi-vegetarian diets consist largely of vegetarian foods, but may include fish or poultry, or sometimes other meats, on an infrequent basis. Those with diets containing fish or poultry may define meat only as mammalian flesh and may identify with vegetarianism. A pescetarian diet has been described as "fish but no other meat". The common use association between such diets and vegetarianism has led vegetarian groups such as the Vegetarian Society to state that diets containing these ingredients are not vegetarian, due to fish and birds being animals.

Etymology
The word vegetarian is on record since 1839, referring to what was previously just described as "vegetable diet". It is a compound of vegetable and the suffix -arian (as in agrarian). The term was popularised with the foundation of the Vegetarian Society in Manchester, UK in 1847. The earliest occurrences of the term seem to be related to Alcott House, a school on the north side of Ham Common, London, opened in July 1838 by James Pierrepont Greaves, from 1841 known as A Concordium, or Industry Harmony College, from which time the institution began to publish its own pamphlet "The Healthian", which provides some of the earliest occurrences of the term "vegetarian".

History
The earliest records of (lacto) vegetarianism come from ancient India and ancient Greece in the 5th century BCE. In the Asian instance the diet was closely connected with the idea of nonviolence towards animals (called ahimsa in India) and was promoted by religious groups and philosophers. Among the Hellenes, Egyptians and others, it had medical or Ritual purification purposes.

Indian emperor Ashoka asserted protection to fauna: ""Twenty-six years after my coronation various animals were declared to be protected – parrots, mainas, aruna, ruddy geese, wild ducks, nandimukhas, gelatas, bats, queen ants, terrapins, boneless fish, vedareyaka, gangapuputaka, sankiya fish, tortoises, porcupines, squirrels, deer, bulls, okapinda, wild asses, wild pigeons, domestic pigeons and all four-footed creatures that are neither useful nor edible. Those nanny goats, ewes and sows which are with young or giving milk to their young are protected, and so are young ones less than six months old. Cocks are not to be caponized, husks hiding living beings are not to be burnt and forests are not to be burnt either without reason or to kill creatures. One animal is not to be fed to another." —Edicts of Ashoka, Fifth Pillar"

Following the Christianisation of the Roman Empire in late antiquity, vegetarianism practically disappeared from Europe as it was in other Continents, except India. Several orders of monks in medieval Europe restricted or banned the consumption of meat for ascetic reasons, but none of them eschewed fish. (The medieval definition of "fish" included such animals as seals, porpoises, dolphins, barnacle geese, puffins, and beavers.)

It re-emerged during the Renaissance, becoming more widespread in the 19th and 20th centuries. In 1847, the first Vegetarian Society was founded in the United Kingdom; Germany, the Netherlands, and other countries followed. The International Vegetarian Union, a union of the national societies, was founded in 1908. In the Western world, the popularity of vegetarianism grew during the 20th century as a result of nutritional, ethical, and more recently, environmental and economic concerns.

Varieties of vegetarianism
There are a number of types of vegetarianism, which exclude or include various foods.
 * Ovo vegetarianism includes eggs but not dairy products.
 * Lacto vegetarianism includes dairy products but not eggs.
 * Ovo-lacto vegetarianism (or lacto-ovo vegetarianism) includes animal/dairy products such as eggs, milk, and honey.
 * Veganism excludes all animal flesh and products, such as milk, honey, and eggs, as well as items refined or manufactured through any such product, such as bone-char refined white sugar or animal-tested baking soda.
 * Raw veganism includes only fresh and uncooked fruit, nuts, seeds, and vegetables. Vegetables can only be cooked up to a certain temperature.
 * Fruitarianism permits only fruit, nuts, seeds, and other plant matter that can be gathered without harming the plant.
 * Sattvic diet (also known as yogic diet), a plant based diet which may also include dairy (not eggs) and honey, but excludes anything from the onion or leek family, red lentils, durian fruit, mushrooms, blue cheeses, fermented foods or sauces, alcoholic drinks and often also excludes coffee, black or green tea, chocolate, nutmeg or any other type of stimulant such as excess sharp spices.
 * Buddhist vegetarianism. Different Buddhist traditions have differing teachings on diet, which may also vary for ordained monks and nuns compared to others. Many interpret the precept 'not to kill' to require abstinence from meat, but not all. In Taiwan, su vegetarianism excludes not only all animal products but also vegetables in the allium family (which have the characteristic aroma of onion and garlic): onion, garlic, scallions, leeks, chives, or shallots.
 * Jain vegetarianism includes dairy but excludes eggs and honey, as well as root vegetables.
 * Macrobiotic diets consist mostly of whole grains and beans.

Within the 'ovo-' groups, there are many who refuse to consume fertilized eggs (with balut being an extreme example); however, such distinction is typically not specifically addressed.

Some vegetarians also avoid products that may use animal ingredients not included in their labels or which use animal products in their manufacturing; for example, sugars that are whitened with bone char, cheeses that use animal rennet (enzymes from animal stomach lining), gelatin (derived from the collagen inside animals' skin, bones and connective tissue), some cane sugar (but not beet sugar) and apple juice/alcohol clarified with gelatin or crushed shellfish and sturgeon, while other vegetarians are unaware of or do not mind such ingredients.

Individuals may label themselves "vegetarian" while practicing a semi-vegetarian diet, as some dictionary definitions describe vegetarianism as including the consumption of fish, or only include mammalian flesh as part of their definition of meat, while other definitions exclude fish and all animal flesh. In other cases, individuals may describe themselves as "flexitarian". These diets may be followed by those who reduce animal flesh consumed as a way of transitioning to a complete vegetarian diet or for health, ethical, environmental, or other reasons. Semi-vegetarian diets include:
 * Pescetarianism, which includes fish and possibly other forms of seafood;
 * Pollotarianism, which includes chicken and possibly other poultry;
 * "Pollo-pescetarian", which includes poultry and fish, or "white meat" only;
 * Macrobiotic diet consisting mostly of whole grains and beans, but may sometimes include fish.

Semi-vegetarianism is contested by vegetarian groups, such as the Vegetarian Society, who state that vegetarianism excludes all animal flesh.

Health effects
Scientific endeavors in the area of vegetarianism have shifted from concerns about nutritional adequacy to investigating health benefits and disease prevention. The Academy of Nutrition and Dietetics 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 non-vegetarians. 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.

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, metabolic syndrome, dementias such as Alzheimer's disease and other disorders. 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. Other studies have shown no significant differences between vegetarians and non-vegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, breast cancer, or prostate cancer. 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.

The relationship between vegetarian diet and bone health remains unclear. According to some studies, a vegetarian lifestyle can be associated with vitamin B12 deficiency and low bone mineral density. However, a study of vegetarian and non-vegetarian adults in Taiwan found no significant difference in bone mineral density between the two groups. Other studies, exploring animal protein's negative effects on bone health, suggest that vegetarians may be less prone to osteoporosis than omnivores, as vegetarian subjects had greater bone mineral density and more bone formation.

The China-Cornell-Oxford Project, a 20-year study conducted by Cornell University, the University of Oxford, and the government of China has established a correlation between the consumption of animal products and a variety of chronic illnesses, such as coronary heart disease, diabetes, and cancers of the breast, prostate and bowel (see The China Study).

Nutrition


Western vegetarian diets are typically high in carotenoids, but relatively low in omega-3 fatty acids and vitamin B12. Vegans can have particularly low intake of vitamin B and calcium if they do not eat enough items such as collard greens, leafy greens, tempeh and tofu (soy). High levels of dietary fiber, folic acid, vitamins C and E, and magnesium, and low consumption of saturated fat are all considered to be beneficial aspects of a vegetarian diet.

Protein
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. Studies at Harvard University as well as other studies conducted in the United States, United Kingdom, Canada, Australia, New Zealand and various European countries, confirmed vegetarian diets provide sufficient protein intake as long as a variety of plant sources are available and consumed. 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 ovo-lacto vegetarian, several vegetable sources have significant amounts of all eight types of essential amino acids, including lupin beans, soy, hempseed, chia seed, amaranth, buckwheat, pumpkin seeds spirulina, pistachios, 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.

Iron
Vegetarian diets typically contain similar levels of iron to non-vegetarian diets, but this has lower bioavailability than iron from meat sources, and its absorption can sometimes be inhibited by other dietary constituents. According to the Vegetarian Resource Group, consuming food that contains vitamin C, such as citrus fruit or juices, tomatoes, or broccoli, is a good way to increase the amount of iron absorbed at a meal. Vegetarian foods rich in iron include black beans, cashews, hempseed, kidney beans, broccoli, lentils, oatmeal, raisins, spinach, cabbage, lettuce, black-eyed peas, soybeans, many breakfast cereals, sunflower seeds, chickpeas, tomato juice, tempeh, molasses, thyme, and whole-wheat bread. The related vegan diets can often be higher in iron than vegetarian diets, because dairy products are low in iron. Iron stores often tend to be lower in vegetarians than non-vegetarians, and a few small studies report very high rates of iron deficiency (up to 40%, and 58% of the respective vegetarian or vegan groups). However, the American Dietetic Association states that iron deficiency is no more common in vegetarians than non-vegetarians (adult males are rarely iron deficient); iron deficiency anaemia is rare no matter the diet.

Vitamin B12
According to the United States National Institutes of Health, vitamin B12 is not generally present in plants and is naturally found in foods of animal origin. Lacto-ovo vegetarians can obtain B12 from dairy products and eggs, and vegans can obtain it from fortified foods (including some soy products and some breakfast cereals) and dietary supplements. Vitamin B12 can also be obtained from fortified yeast extract products.

The recommended dietary allowance of B12 in the United States is, per day, 0.4 mcg (0–6 months), rising to 1.8 mcg (9–13 years), 2.4 mcg (14+ years), and 2.8 mcg (lactating female). While the body's daily requirement for vitamin B12 is very small, deficiency of the vitamin is very serious leading to anemia and irreversible nerve damage.

Fatty acids
Plant-based, or vegetarian, sources of Omega 3 fatty acids include soy, walnuts, pumpkin seeds, canola oil, kiwifruit, hempseed, algae, chia seed, flaxseed, echium seed and leafy vegetables such as lettuce, spinach, cabbage and purslane. Purslane contains more Omega 3 than any other known leafy green. Olives (and olive oil) are another important plant source of unsaturated fatty acids. Plant foods can provide alpha-linolenic acid which the human body uses to synthesize the long-chain n-3 fatty acids EPA and DHA. EPA and DHA can be obtained directly in high amounts from oily fish or fish oils. Vegetarians, and particularly vegans, have lower levels of EPA and DHA than meat-eaters. While the health effects of low levels of EPA and DHA are unknown, it is unlikely that supplementation with alpha-linolenic acid will significantly increase levels. Recently, some companies have begun to market vegetarian DHA supplements containing seaweed extracts. Similar supplements providing both DHA and EPA have also begun to appear. Whole seaweeds are not suitable for supplementation because their high iodine content limits the amount that may be safely consumed. However, certain algae such as spirulina are good sources of gamma-linolenic acid (GLA), alpha-linolenic acid (ALA), linoleic acid (LA), stearidonic acid (SDA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA).

Calcium
Calcium intake in vegetarians is similar to non-vegetarians. Some impaired bone mineralisation has been found among vegans who do not consume enough leafy greens, which are sources of abundant calcium. However, this is not found in lacto-ovo vegetarians. Some significant sources of calcium include broccoli, beans, peas, lentils, cabbage, lettuce, collard greens, bok choy, kale, and turnip greens. Spinach, swiss chard and beet greens are high in calcium, but the calcium is bound to oxalate and therefore it is poorly absorbed.

Vitamin D
Vitamin D needs can be met via the human body's own generation upon sufficient and sensible exposure to ultraviolet (UV) light in sunlight. Products including milk, soy milk and cereal grains may be fortified to provide a source of Vitamin D For those who do not get adequate sun exposure and/or food sources, Vitamin D supplementation may be necessary.

Vitamin D2

 * Plants
 * Alfalfa (Medicago sativa subsp. sativa), shoot: 4.8 μg (192 IU) vitamin D2, 0.1 μg (4 IU) vitamin D3
 * Fungus, from USDA nutrient database:
 * Mushrooms, portabella, exposed to ultraviolet light, raw: Vitamin D2: 11.2 μg (446 IU)
 * Mushrooms, portabella, exposed to ultraviolet light, grilled: Vitamin D2: 13.1 μg (524 IU)
 * Mushrooms, shiitake, dried: Vitamin D2: 3.9 μg (154 IU)
 * Mushrooms, shiitake, raw: Vitamin D2: 0.4 μg (18 IU)
 * Mushrooms, portabella, raw: Vitamin D2: 0.3 μg (10 IU)
 * Mushroom powder, any species, illuminated with sunlight or artificial ultraviolet light sources

Vitamin D2, or ergocalciferol is found in fungus (except alfalfa which is a plantae) and created from viosterol, which in turn is created when ultraviolet light activates ergosterol (which is found in fungi and named as a sterol from ergot). Any UV-irradiated fungus including yeast form vitamin D2. Human bioavailability of vitamin D2 from vitamin D2-enhanced button mushrooms via UV-B irradiation is effective in improving vitamin D status and not different from a vitamin D2 supplement according to study. For example, Vitamin D2 from UV-irradiated yeast baked into bread is bioavailable. By visual assessment or using a chromometer, no significant discoloration of irradiated mushrooms, as measured by the degree of "whiteness", was observed making it hard to discover if they have been treated without labeling. Claims have been made that a normal serving (approx. 3 oz or 1/2 cup, or 60 grams) of mushrooms treated with ultraviolet light increase their vitamin D content to levels up to 80 micrograms, or 2700 IU if exposed to just 5 minutes of UV light after being harvested.

Longevity
A 1999 metastudy combined data from five studies from western countries. The metastudy reported mortality ratios, where lower numbers indicated fewer deaths, for fish eaters to be 0.82, vegetarians to be 0.84, occasional meat eaters (eat meat less than once per week) to be 0.84. Regular meat eaters had the base mortality rate of 1.0, while the number for vegans was very uncertain (anywhere between 0.7 and 1.44) due to too few data points. The study reported the numbers of deaths in each category, and expected error ranges for each ratio, and adjustments made to the data. However, the "lower mortality was due largely to the relatively low prevalence of smoking in these [vegetarian] cohorts". Out of the major causes of death studied, only one difference in mortality rate was attributed to the difference in diet, as the conclusion states: "...vegetarians had a 24% lower mortality from ischaemic heart disease than non-vegetarians, but no associations of a vegetarian diet with other major causes of death were established".

In Mortality in British vegetarians, a similar conclusion is drawn: "British vegetarians have low mortality compared with the general population. Their death rates are similar to those of comparable non-vegetarians, suggesting that much of this benefit may be attributed to non-dietary lifestyle factors such as a low prevalence of smoking and a generally high socio-economic status, or to aspects of the diet other than the avoidance of meat and fish."

The Adventist Health Studies is ongoing research that documents the life expectancy in Seventh-day Adventists. This is the only study among others with similar methodology which had favourable indication for vegetarianism. The researchers found that a combination of different lifestyle choices could influence life expectancy by as much as 10 years. Among the lifestyle choices investigated, a vegetarian diet was estimated to confer an extra 1–1/2 to 2 years of life. The researchers concluded that "the life expectancies of California Adventist men and women are higher than those of any other well-described natural population" at 78.5 years for men and 82.3 years for women. The life expectancy of California Adventists surviving to age 30 was 83.3 years for men and 85.7 years for women.

The Adventist health study is again incorporated into a metastudy titled "Does low meat consumption increase life expectancy in humans?" published in American Journal of Clinical Nutrition, which concluded that low meat eating (less than once per week) and other lifestyle choices significantly increase life expectancy, relative to a group with high meat intake. The study concluded that "The findings from one cohort of healthy adults raises the possibility that long-term (≥ 2 decades) adherence to a vegetarian diet can further produce a significant 3.6-y increase in life expectancy." However, the study also concluded that "Some of the variation in the survival advantage in vegetarians may have been due to marked differences between studies in adjustment for confounders, the definition of vegetarian, measurement error, age distribution, the healthy volunteer effect, and intake of specific plant foods by the vegetarians." It further states that "This raises the possibility that a low-meat, high plant-food dietary pattern may be the true causal protective factor rather than simply elimination of meat from the diet." In a recent review of studies relating low-meat diet patterns to all-cause mortality, Singh noted that "5 out of 5 studies indicated that adults who followed a low meat, high plant-food diet pattern experienced significant or marginally significant decreases in mortality risk relative to other patterns of intake."

Statistical studies, such as comparing life expectancy with regional areas and local diets in Europe also have found life expectancy considerably greater in southern France, where a low meat, high plant Mediterranean diet is common, than northern France, where a diet with high meat content is more common.

A study by the Institute of Preventive and Clinical Medicine, and Institute of Physiological Chemistry looked at a group of 19 vegetarians (lacto-ovo) and used as a comparison a group of 19 omnivorous subjects recruited from the same region. The study found that this group of vegetarians (lacto-ovo) have a significantly higher amount of plasma carboxymethyllysine and advanced glycation endproducts (AGEs) compared to this group of non-vegetarians. Carboxymethyllysine is a glycation product which represents "a general marker of oxidative stress and long-term damage of proteins in aging, atherosclerosis and diabetes" and "[a]dvanced glycation end products (AGEs) may play an important adverse role in process of atherosclerosis, diabetes, aging and chronic renal failure".

Medical use
In Western medicine, patients are sometimes advised to adhere to a vegetarian diet. Vegetarian diets have been used as a treatment for rheumatoid arthritis, but the evidence is inconclusive whether this is effective. Certain alternative medicines, such as Ayurveda and Siddha, prescribe a vegetarian diet as a normal procedure. Maya Tiwari notes that Ayurveda recommends small portions of meat for some people, though "the rules of hunting and killing the animal, practiced by the native peoples, were very specific and detailed". Now that such methods of hunting and killing are not observed, she does not recommend the use of "any animal meat as food, not even for the Vata types".

Physiology
Humans are omnivorous, capable of consuming a wide variety of plant and animal material. Nutritional experts believe that early hominids evolved into eating meat as a result of huge climatic changes that took place three to four million years ago, when forests and jungles dried up and became open grasslands and opened hunting and scavenging opportunities.

Animal-to-human disease transmissions
The consumption of meat can cause a transmission of a number of diseases from animals to humans. The connection between infected animal and human illness is well established in the case of salmonella; an estimated one-third to one-half of all chicken meat marketed in the United States is contaminated with salmonella. Only recently, however, have scientists begun to suspect that there is a similar connection between animal meat and human cancer, birth defects, mutations, and many other diseases in humans. The rate of disease among chickens is so high that the Department of Labor has ranked the poultry industry as one of the most hazardous occupations. 20% of all cows are afflicted with a variety of cancer known as bovine leukemia virus (BLV). Studies have increasingly linked BLV with HTLV-1, the first human retrovirus discovered to cause cancer. Scientists have found that a bovine immunodeficiency virus (BIV), the equivalent of the AIDS virus in cows, can also infect human cells. It is supposed that BIV may have a role in the development of a number of malignant or slow viruses in humans.

The proximity of animals in industrial-scale animal farming leads to an increased rate of disease transmission.

"Transmission of animal influenza viruses to humans has been documented, but illness from such cases is rare compared to that caused by the now common human-adapted older influenza viruses, transferred from animals to humans in the more distant past. The first documented case was in 1959, and in 1998, 18 new human cases of H5N1 influenza were diagnosed, in which six people died. In 1997 more cases of H5N1 avian influenza were found in chickens in Hong Kong."

Whether tuberculosis originated in cattle and was then transferred to humans, or diverged from a common ancestor infecting a different species, is currently unclear. The strongest evidence for a domestic-animal origin exists for measles and pertussis, although the data do not exclude a non-domestic origin.

According to the 'Hunter Theory', the "simplest and most plausible explanation for the cross-species transmission" the AIDS virus was transmitted from a chimpanzee to a human when a bushmeat hunter was bitten or cut while hunting or butchering an animal.

Historian Norman Cantor suggests the Black Death might have been a combination of pandemics including a form of anthrax, a cattle murrain. He cites many forms of evidence including the fact that meat from infected cattle was known to have been sold in many rural English areas prior to the onset of the plague.

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". Other studies and statements by dietitians and counselors support this conclusion.

General
Various ethical reasons have been suggested for choosing vegetarianism, usually predicated on the interests of non-human animals. In many societies, controversy and debate have arisen over the ethics of eating animals. Some people, while not vegetarians, refuse to eat the flesh of certain animals due to cultural taboo, such as cats, dogs, horses or rabbits. Others support meat eating for scientific, nutritional and cultural reasons, including religious ones. Some meat eaters abstain from the meat of animals reared in particular ways, such as factory farms, or avoid certain meats, such as veal or foie gras. Some people follow vegetarian or vegan diets not because of moral concerns involving the raising or consumption of animals in general, but because of concerns about the specific treatment and practises involved in the raising and slaughter of animals, i.e. factory farming and the industrialisation of animal slaughter. Others still avoid meat because meat production is claimed to place a greater burden on the environment than production of an equivalent amount of plant protein.

Ethical objections based on consideration for animals are generally divided into opposition to the act of killing in general, and opposition to certain agricultural practices surrounding the production of meat.

Ethics of killing for food
Princeton University professor and founder of the animal rights movement, Peter Singer, believes that if alternative means of survival exist, one ought to choose the option that does not cause unnecessary harm to animals. Most ethical vegetarians argue that the same reasons exist against killing animals to eat as against killing humans to eat. Singer, in his book Animal Liberation listed possible qualities of sentience in non-human creatures that gave such creatures the scope to be considered under utilitarian ethics, and this has been widely referenced by animal rights campaigners and vegetarians. Ethical vegetarians also believe that killing an animal, like killing a human, can only be justified in extreme circumstances and that consuming a living creature for its enjoyable taste, convenience, or nutritional value is not sufficient cause. Another common view is that humans are morally conscious of their behaviour in a way other animals are not, and therefore subject to higher standards.

Opponents of ethical vegetarianism argue that animals are not moral equals to humans and so consider the comparison of eating livestock with killing people to be fallacious. This view does not excuse cruelty, but maintains that animals do not possess the rights a human has.

Milk and eggs
One of the main differences between a vegan and a typical vegetarian diet is the avoidance of both eggs and dairy products such as milk, cheese, butter and yogurt. Ethical vegans do not consume dairy or eggs because they state that their production causes the animal suffering and/or a premature death.

To produce milk from dairy cattle, calves are separated from their mothers soon after birth and slaughtered or fed milk replacer in order to retain the cows milk for human consumption. Vegans state that this breaks the natural mother and calf bond. Unwanted male calves are either slaughtered at birth or sent for veal production. To prolong lactation, dairy cows are almost permanently kept pregnant through artificial insemination. After about five years, once the cows milk production has dropped, they are considered "spent" and sent to slaughter for hamburger meat and their hides. A dairy cow's natural life expectancy is about twenty years.

In battery cage and free-range egg production, unwanted male chicks are culled or discarded at birth during the process of securing a further generation of egg-laying hens.

Treatment of animals
Ethical vegetarianism has become popular in developed countries particularly because of the spread of factory farming, faster communications, and environmental consciousness. Some believe that the current mass demand for meat cannot be satisfied without a mass-production system that disregards the welfare of animals, while others believe that practices like well-managed free-ranging and consumption of game, particularly from species whose natural predators have been significantly eliminated, could substantially alleviate the demand for mass-produced meat.

Classical Greek and Roman philosophy
Ancient Greek philosophy has a long tradition of vegetarianism. Pythagoras was reportedly vegetarian (and studied at Mt. Carmel, where some historians say there was a vegetarian community), as his followers were expected to be.

Roman writer Ovid concluded his magnum opus Metamorphoses, in part, with the impassioned argument (uttered by the character of Pythagoras) that in order for humanity to change, or metamorphose, into a better, more harmonious species, it must strive towards more humane tendencies. He cited vegetarianism as the crucial decision in this metamorphosis, explaining his belief that human life and animal life are so entwined that to kill an animal is virtually the same as killing a fellow human.

"Everything changes; nothing dies; the soul roams to and fro, now here, now there, and takes what frame it will, passing from beast to man, from our own form to beast and never dies...Therefore lest appetite and greed destroy the bonds of love and duty, heed my message! Abstain! Never by slaughter dispossess souls that are kin and nourish blood with blood!"

Religion and diet
Jainism teaches vegetarianism as moral conduct as do some major sects of Hinduism. Buddhism in general does not prohibit meat eating, while Mahayana Buddhism encourages vegetarianism as beneficial for developing compassion. Other denominations that advocate a vegetarian diet include the Seventh-day Adventists, the Rastafari movement, the Ananda Marga movement and the Hare Krishnas. Sikhism  does not equate spirituality with diet and does not specify a vegetarian or meat diet.

Bahá'í Faith
While there are no dietary restrictions in the Bahá'í Faith, `Abdu'l-Bahá, the son of the religion's founder, noted that a vegetarian diet consisting of fruits and grains was desirable, except for people with a weak constitution or those that are sick. He stated that there are no requirements that Bahá'ís become vegetarian, but that a future society should gradually become vegetarian. `Abdu'l-Bahá also stated that killing animals was contrary to compassion. While Shoghi Effendi, the head of the Bahá'í Faith in the first half of the 20th century, stated that a purely vegetarian diet would be preferable since it avoided killing animals, both he and the Universal House of Justice, the governing body of the Bahá'ís have stated that these teachings do not constitute a Bahá'í practice and that Bahá'ís can choose to eat whatever they wish but should be respectful of others' beliefs.

Buddhism


Theravadins in general eat meat. If Buddhist monks "see, hear or know" a living animal was killed specifically for them to eat, they must refuse it or else incur an offense. However, this does not include eating meat which was given as alms or commercially purchased. In the Theravada canon, Buddha did not make any comment discouraging them from eating meat (except specific types, such as human, elephant, horse, dog, snake, lion, tiger, leopard, bear, and hyena flesh ) but he specifically refused to institute vegetarianism in his monastic code when a suggestion had been made.

In several Sanskrit texts of Mahayana Buddhism, Buddha instructs his followers to avoid meat. However, each branch of Mahayana Buddhism selects which sutra to follow, and some branches, including the majority of Tibetan and Japanese Buddhists, do eat meat, while many Chinese Buddhist branches do not.

Christianity
There is no specific teaching on diet in traditional Christianity—except that nothing is forbidden on religious principles. The eating of meat is neither encouraged nor discouraged. Christians have always been free to make their own decisions about what to eat; however, there are groups within Christianity that practice specific dietary restrictions for various reasons.

The early sect known as the Ebionites are considered to have practiced vegetarianism. Surviving fragments from their Gospel indicate their belief that – as Christ is the Passover sacrifice and eating the Passover lamb is no longer required – a vegetarian diet may (or should) be observed. However, orthodox Christianity does not accept their teaching as authentic. Indeed, their specific injunction to strict vegetarianism was cited as one of the Ebionites' "errors".

At a much later time, the Bible Christian Church founded by Reverend William Cowherd in 1809 followed a vegetarian diet. Cowherd was one of the philosophical forerunners of the Vegetarian Society. Cowherd encouraged members to abstain from eating of meat as a form of temperance.

Seventh-day Adventists are encouraged to engage in healthy eating practices, and ova-lacto-vegetarian diets are recommended by the General Conference of Seventh-day Adventists Nutrition Council (GCNC). They have also sponsored and participated in many scientific studies exploring the impact of dietary decisions upon health outcomes. The GCNC has in addition adapted the USDA's food pyramid for a vegetarian dietary approach. However, the only kinds of meat specifically frowned upon by the SDA health message are unclean meats, or those forbidden in scripture.

Additionally, some monastic orders follow a vegetarian diet, and members of the Orthodox Church follow a vegan diet during fasts. There is also a strong association between the Quakers and vegetarianism dating back at least to the 18th century. The association grew in prominence during the 19th century, coupled with growing Quaker concerns in connection with alcohol consumption, vivisection and social purity. The association between the Quaker tradition and vegetarianism, however, becomes most significant with the founding of the Friends' Vegetarian Society in 1902 "to spread a kindlier way of living amongst the Society of Friends."

According to Canon Law, Roman Catholics are required to abstain from meat (defined as all animal flesh excluding water animals) on Ash Wednesday, Good Friday, all Fridays of Lent, and all other Fridays (subject to the local bishop) as an act of penance.

Hinduism
Paths of Hinduism hold vegetarianism as an ideal. There are three main reasons for this: the principle of nonviolence (ahimsa) applied to animals; the intention to offer only "pure" (vegetarian) food to a deity and then to receive it back as prasad; and the conviction that a sentient diet is beneficial for a healthy body and mind and that non-vegetarian food is detrimental for the mind and for spiritual development.

However, the food habits of Hindus vary according to their community and according to regional traditions. Historically and currently, those Hindus who eat meat prescribe Jhatka meat.

Islam
Followers of Islam, or Muslims, have the freedom of choice to be vegetarian for medical reasons or if they do not personally like the taste of meat. However, the choice to become vegetarian for non-medical reasons can sometimes be controversial. Though some more traditional Muslims may keep quiet about their vegetarian diet, the number of vegetarian Muslims is increasing.

Vegetarianism has been practiced by some influential Muslims including the Iraqi theologian, female mystic and poet Râbi‘ah al-‘Adawîyah of Basrah, who died in the year 801, and the Sri Lankan Sufi master Bawa Muhaiyaddeen who established The Bawa Muhaiyaddeen Fellowship of North America in Philadelphia. The former Indian president Dr. A. P. J. Abdul Kalam is also famously a vegetarian.

In January 1996, The International Vegetarian Union announced the formation of the Muslim Vegetarian/Vegan Society.

Many non-vegetarian Muslims will select vegetarian (or seafood) options when dining in non-halal restaurants. However, this is a matter of not having the right kind of meat rather than preferring not to eat meat on the whole.

Jainism
Followers of Jainism believe that all living organisms whether they are micro-organism are living and have a soul, and have one or more senses out of five senses and they go to great lengths to minimise any harm to any living organism. Most Jains are lacto-vegetarians but more devout Jains do not eat root vegetables because they believe that root vegetables contain a lot more micro-organisms as compared to other vegetables, and that, by eating them, violence of these micro-organisms is inevitable. So they focus on eating beans and fruits, whose cultivation do not involve killing of a lot of micro-organisms. No products obtained from dead animals are allowed, because when a living beings dies, a lot of micro-organisms (called as decomposers) will reproduce in the body which decomposes the body, and in eating the dead bodies, violence of decomposers is inevitable. Jain monks usually do a lot of fasting, and when they knew through spiritual powers that their life is very little, they start fasting until death. Some particularly dedicated individuals are fruitarians. Honey is forbidden, because honey is a collection of eggs, excreta, dead bees, and saliva of bees. Some Jains do not consume plant parts that grow underground such as roots and bulbs, because tiny animals may be killed when the plants are pulled up.

Judaism
While it is neither required nor prohibited for Jews to eat meat, a number of medieval scholars of Jewish religion (e.g., Joseph Albo and Isaac Arama) regard vegetarianism as a moral ideal, not just because of a concern for the welfare of animals, but because the slaughter of animals might cause the individual who performs such acts to develop negative character traits. One modern-day scholar who is in favour of vegetarianism is the late Rabbi Abraham Isaac Kook, the Chief Rabbi of Mandate Palestine. In his writings, Rabbi Kook speaks of vegetarianism as an ideal, and points to the fact that Adam did not partake of the flesh of animals, as all humans and animals were originally commanded by God to only eat plants. In context, Rabbi Kook makes those comments in his portrayal of the eschatological (messianic) era. However, he personally refrained from eating meat except on the Sabbath and Festivals, and one of his leading disciples, Rabbi David Cohen, known as the "Nazirite" of Jerusalem, was a devout vegetarian. Several other members of Rabbi Kook's circle were also vegetarians.

According to some Kabbalists, only a mystic, who is able to sense and elevate the reincarnated human souls and "divine sparks", is permitted to consume meat, though eating the flesh of an animal might still cause spiritual damage to the soul. A number of Orthodox Jewish vegetarian groups and activists promote such ideas and believe that the halakhic permission to eat meat is a temporary leniency for those who are not ready yet to accept the vegetarian diet.

The Torah also commands people to ritually slaughter animals when killing them, and goes into precise detail on the rituals of both animal sacrifice and ordinary slaughter (shechita). According to medieval sage Rabbi Shlomo Ephraim Luntschitz, author of the Torah commentary Kli Yakar, the complexity of these laws was intended to discourage the consumption of meat.

Rastafari
Within the Afro-Caribbean community, a minority are Rastafari and follow the dietary regulations with varying degrees of strictness. The most orthodox eat only "Ital" or natural foods, in which the matching of herbs or spices with vegetables is the result of long tradition originating from the African ancestry and cultural heritage of Rastafari. Most Rastafari are vegetarian.

Sikhism
The tenets of Sikhism do not advocate a particular stance on either vegetarianism or the consumption of meat, but leave the decision of diet to the individual. The tenth guru, Guru Gobind Singh, however, prohibited "Amritdhari" Sikhs, or those that follow the Sikh Rehat Maryada (the Official Sikh Code of Conduct) from eating Kutha meat, or meat which has been obtained from animals which have been killed in a ritualistic way. This is understood to have been for the political reason of maintaining independence from the then-new Muslim hegemony, as Muslims largely adhere to the ritualistic halal diet.

"Amritdharis" that belong to some Sikh sects (e.g. Akhand Kirtani Jatha, Damdami Taksal, Namdhari and Rarionwalay, etc.) are vehemently against the consumption of meat and eggs (though they do consume and encourage the consumption of milk, butter and cheese). This vegetarian stance has been traced back to the times of the British Raj, with the advent of many new Vaishnava converts. In response to the varying views on diet throughout the Sikh population, Sikh Gurus have sought to clarify the Sikh view on diet, stressing their preference only for simplicity of diet. Guru Nanak said that over-consumption of food (Lobh, Greed) involves a drain on the Earth's resources and thus on life. Passages from the Guru Granth Sahib (the holy book of Sikhs, also known as the Adi Granth) say that it is "foolish" to argue for the superiority of animal life, because though all life is related, only human life carries more importance: "Only fools argue whether to eat meat or not. Who can define what is meat and what is not meat? Who knows where the sin lies, being a vegetarian or a non-vegetarian?" The Sikh langar, or free temple meal, is largely lacto-vegetarian, though this is understood to be a result of efforts to present a meal that is respectful of the diets of any person who would wish to dine, rather than out of dogma.

Environment and diet
Environmental vegetarianism is based on the concern that the production of meat and animal products for mass consumption, especially through factory farming, is environmentally unsustainable. According to a 2006 United Nations initiative, the livestock industry is one of the largest contributors to environmental degradation worldwide, and modern practices of raising animals for food contribute on a "massive scale" to air and water pollution, land degradation, climate change, and loss of biodiversity. The initiative concluded that "the livestock sector emerges as one of the top two or three most significant contributors to the most serious environmental problems, at every scale from local to global."

In addition, animal agriculture is a large source of greenhouse gases. According to a 2006 report it is responsible for 18% of the world's greenhouse gas emissions as estimated in 100-year CO2 equivalents. Livestock sources (including enteric fermentation and manure) account for about 3.1 percent of US anthropogenic GHG emissions expressed as carbon dioxide equivalents. This EPA estimate is based on methodologies agreed to by the Conference of Parties of the UNFCCC, with 100-year global warming potentials from the IPCC Second Assessment Report used in estimating GHG emissions as carbon dioxide equivalents.

Meat produced in a laboratory (called in vitro meat) may be more environmentally sustainable than regularly produced meat. Reactions of vegetarians vary. Rearing a relatively small number of grazing animals can be beneficial, as the Food Climate Research Network at Surrey University reports: "A little bit of livestock production is probably a good thing for the environment.

In May 2009, Ghent, Belgium, was reported to be "the first [city] in the world to go vegetarian at least once a week" for environmental reasons, when local authorities decided to implement a "weekly meatless day". Civil servants would eat vegetarian meals one day per week, in recognition of the United Nations' report. Posters were put up by local authorities to encourage the population to take part on vegetarian days, and "veggie street maps" were printed to highlight vegetarian restaurants. In September 2009, schools in Ghent are due to have a weekly veggiedag ("vegetarian day") too.

Labor conditions and diet
Some groups, such as PETA, promote vegetarianism as a way to offset poor treatment and working conditions of workers in the contemporary meat industry. These groups cite studies showing the psychological damage caused by working in the meat industry, especially in factory and industrialised settings, and argue that the meat industry violates its labourers' human rights by assigning difficult and distressing tasks without adequate counselling, training and debriefing. However, the working conditions of agricultural workers as a whole, particularly non-permanent workers, remain poor and well below conditions prevailing in other economic sectors. Accidents, including pesticide poisoning, among farmers and plantation workers contribute to increased health risks, including increased mortality. According to the International Labour Organization, agriculture is one of the three most dangerous jobs in the world.

Economics and diet
Similar to environmental vegetarianism is the concept of economic vegetarianism. An economic vegetarian is someone who practices vegetarianism from either the philosophical viewpoint concerning issues such as public health and curbing world starvation, the belief that the consumption of meat is economically unsound, part of a conscious simple living strategy or just out of necessity. According to the Worldwatch Institute, "Massive reductions in meat consumption in industrial nations will ease their health care burden while improving public health; declining livestock herds will take pressure off rangelands and grainlands, allowing the agricultural resource base to rejuvenate. As populations grow, lowering meat consumption worldwide will allow more efficient use of declining per capita land and water resources, while at the same time making grain more affordable to the world's chronically hungry."



Demographics
A research study conducted on more than 8,000 people, and published in the British Medical Journal, suggested that children with an above-average IQ may have a higher chance of becoming vegetarians in their adulthood. Vegetarians had an average childhood IQ of 105 compared with 100 for non-vegetarians. No difference in IQ score was found between strict vegetarians and those who reported eating fish or chicken.

Prejudice researcher Gordon Hodson observes that vegetarians and vegans frequently face discrimination because eating meat is held as a cultural norm, as do atheists and asexuals because religion and sex hold similar status.

Gender
A 1992 market research study conducted by the Yankelovich research organisation concluded that "of the 12.4 million people [in the US] who call themselves vegetarian, 68% are female, while only 32% are male".

At least one study indicates that vegetarian women are more likely to have female babies. A study of 6,000 pregnant women in 1998 "found that while the national average in Britain is 106 boys born to every 100 girls, for vegetarian mothers the ratio was just 85 boys to 100 girls". Catherine Collins of the British Dietetic Association has dismissed this as a "statistical fluke" given that it is actually the male's genetic contribution which determines the sex of a baby.