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Research and general acceptance



Ovolactovegetarians, who are also known as lacto-ovovegetarians, are vegetarians who do not eat fish, poultry, or red meat but accept eggs, milk, and honey as part of their diet on the grounds that these foods can be obtained without killing the animals who produce them. The ovo- part of the name comes from the Latin word for egg, while lacto- is derived from the Latin word for milk. In the West, ovolactovegetarians are the largest subgroup of vegetarians. As a result, most restaurants, institutional food services, cookbooks, and prepared foods that identify themselves as ‘vegetarian’ without further qualification are ovo-lactovegetarian. Similarly, travelers who order special ‘vegetarian’ meals from an airline before departure will be given ovolactovegetarian food unless they are more specific.

The reader should note, however, that some other cultures define ‘vegetarian’ differently. In Japan, for example, many people think of fish as included in a vegetarian diet. Practitioners of Hinduism, who account for the largest single group of vegetarians worldwide, do not eat eggs, and therefore follow a lactovegetarian diet.


Vegetarianism in general has existed for thousands of years, although the anatomical and archaeological evidence indicates that prehistoric humans were not vegetarians. The pattern of human dentition (teeth adapted for tearing meat as well as grinding plant matter), the length of the human digestive tract, and the secretion of pepsin (an enzyme that is necessary for digesting meat) by the human stomach are all indications that humans evolved as omnivores, or animals that consume both plant and animal matter.

Religious faith is the oldest known motive for consuming a vegetarian diet. 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 percent—than any other faith or political conviction. The Hindu religion does not, however, endorse ovolactovegetarianism, as observant Hindus may not eat eggs. Christians and Jews who are vegetarians for religious reasons, however, are usually either ovolactovegetarians or vegans.

Ovolactovegetarianism as it is currently practiced by most Westerners is largely a byproduct of the animal rights movement that began in the mid-nineteenth century with the formation of the first societies for the prevention of cruelty to animals. The vegetarian groups of the late nineteenth century began by excluding meat, poultry, and fish from the diet on the grounds that these foods require the slaughter of animals, whereas the use of cow’s milk and hen’s eggs


Carnivore— An animal whose diet consists mostly or entirely of meat. Cats, wolves, snakes, birds of prey, frogs, sharks, spiders, seals, and penguins are all carnivores.

ietitian— A health care professional who specializes in individual or group nutritional planning, public education in nutrition, or research in food science. To be licensed as a registered dietitian (RD) in the United States, a person must complete a bachelor’s degree in a nutrition-related field and pass a state licensing examination. Dietitians are also called nutritionists.

Factory farming— A term that refers to the application of techniques of mass production borrowed from industry to the raising of livestock, poultry, fish, and crops. It is also known as industrial agriculture.

Lactose intolerance— A condition in which the body does not produce enough lactase, an enzyme needed to digest lactose (milk sugar). Ovolactovege-tarians with lactose intolerance often choose to use soy milk, almond milk, or other milk substitutes as sources of protein.

Lactovegetarian— A vegetarian who uses milk, yogurt, and cheese in addition to plant-based foods, but does not eat eggs.

Omnivore— An animal whose teeth and digestive tract are adapted to consume either plant or animal matter. The term does not mean, however, that a given species consumes equal amounts of plant and animal products. Omnivores include bears, squirrels, opossums, rats, pigs, foxes, chickens, crows, monkeys, most dogs, and humans.

Ovolactovegetarian— A vegetarian who consumes eggs and dairy products as well as plant-based foods. The official diet recommended to Seventh-day Adventists is ovolactovegetarian.

vovegetarian— A vegetarian who eats eggs in addition to plant-based foods but does not use milk or other dairy products.

Pepsin— A protease enzyme in the gastric juices of carnivorous and omnivorous animals that breaks down the proteins found in meat. Its existence in humans is considered evidence that humans evolved as omnivores.

Vegan— A vegetarian who excludes all animal products from the diet, including those that can be obtained without killing the animal. Vegans are also known as strict vegetarians.

does not. These groups, however, were formed before the rise of modern factory farming, which often results in inhumane living conditions for dairy cows and egg-producing hens. As a result, many contemporary ovo-lactovegetarians insist on purchasing their eggs or dairy products from small farmers who do not use factory-farming methods.


The 2003 vegetarian food guide

Ovolactovegetarianism entered the medical mainstream in 2003 when the American Dietetic Association (ADA) and the Dietitians of Canada (DC) jointly issued ‘A New Food Guide for North American Vegetarians.’ This document contained the first major revisions of the familiar U.S. Department of Agriculture (USDA) food guide pyramid (originated 1912, modified in 1942 and 1992) and Canada’s Food Guide to Healthy Eating (CFGHE; originated 1942, modified in 1992) intended for vegetarians. While the 1992 food guides were the first to consider overnutri-tion as a serious health problem, and emphasized the importance of plant foods in the diet, they did not include guidelines for planning vegetarian diets. The 2003 food guide borrowed the general concept of food groups from the older guides, but reclassified foods into five plant-based groups:

  • Grains: The foundation of an ovolactovegetarian diet. Whole grains are best, but enriched refined grains are also acceptable.
  • Vegetables and fruits: The ADA and DC recommend that vegetarians choose both vegetables and fruits rather than using only one or the other.
  • Legumes, nuts, and other protein-rich foods: Legumes include soy milk and tofu. Dairy products used by ovolactovegetarians also fall into this category, as do meat substitutes.
  • Fats: Ovolactovegetarians require plant-based sources of n-3 fats because they do not eat fish.
  • Calcium-rich foods: Adult ovolactovegetarians require eight servings from this category each day. Each serving, however, counts toward one of the other food choices, as calcium-rich foods can be found across the other food groups.

Some specific vegetarian diets

Ovolactovegetarian diets can accommodate a wide variety of regional and ethnic cuisines as well as different philosophical or religious approaches. The following are some of the possible choices:

MEDITERRANEAN DIETS. Mediterranean diets were not purely ovolactovegetarian in their origins. They are, however, easily adapted to ovolactovegetarian food choices; in fact, several European studies of the beneficial effects of vegetarian diets have been based on ovolactovegetarian modifications of Greek and Spanish Mediterranean diets. These diets are high in their use of whole grains, fruits, nuts, and high-fiber vegetables, and therefore appeal to many people because of their wide choice of flavorful foods.

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. The Ornish diet can be used by ovolactovegetarians because it allows 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, fresh vegetables and fruits; moderate use of nuts, seeds, and low-fat dairy products; and limited use of eggs. The church has its own professional organization for dietitians, which is affiliated with the ADA, and encourages all its members to follow the ADA guidelines for vegetarians.


Ovolactovegetarian diets are adopted by people in developed countries primarily for ethical or religious reasons rather than economic necessity. Another more recent reason is the growing perception that plant-based diets are a form of preventive health care for people at increased risk of such diseases as heart disease, type 2 diabetes and some forms of cancer. According to a survey conducted by the editors of Vegetarian Journal in 1997, 82% of the respondents gave health concerns as their primary reason for becoming vegetarians, with animal rights a close second.


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 are associated with a vegetarian diet, especially the ovolactovegetarian regimen recommended by the church. In particular, SDAs were only half as likely to develop type 2 (adult-onset) diabetes as were nonvegetarian Caucasians. Although it is possible to gain weight on an ovolactovegetarian diet, most people lose weight, especially in the first few months; and most vegetarians have lower body mass indices (an important diagnostic criterion of obesity ) than their meat-eating counterparts.

Several studies carried out in Germany and Austria reported in 2006 that ovolactovegetarian diets appear to lower the risk of rheumatoid arthritis, osteoporosis, kidney disease, gallstones, diverticulitis, and dementia as well as heart attacks, stroke, and diabetes. In addition, a team of Spanish researchers reported that an ovolactovegetarian version of the traditional Spanish Mediterranean diet was effective in lowering blood cholesterol levels in younger as well as middle-aged subjects.


The ADA strongly recommends that people consult a registered dietitian as well as their primary physician before starting an ovolactovegetarian diet. The reason for this precaution is the variety of dietary regimens that could be called ovolactovegetarian as well as the variations in height, weight, age, genetic inheritance, food preferences, level of activity, geographic location, and preexisting health problems among people. People with high blood cholesterol levels may need to limit their consumption of eggs as much as possible even though this type of vegetarian diet allows the use of eggs. A nutritionist can also help design a diet that a new ovolactovegetarian will enjoy eating as well as getting adequate nourishment and other health benefits.


The longstanding concern about vegetarian diets in general is the risk of nutritional deficiencies, particularly for such important nutrients as protein


  • Would you recommend a vegan diet rather than an ovolactovegetarian diet?
  • Have any of your other patients used either a modified Mediterranean diet or the Seventh-day Adventist ovolactovegetarian diet? Would you recommend these diets?
  • Will I need to take vitamins or other dietary supplements if I adopt an ovolactovegetarian diet?
  • Have you ever tried this type of vegetarian diet yourself?
  • What is your opinion of the EPIC study and other recent long-term studies of ovolactovegetarians?

minerals (iron, calcium, and zinc), vitamins (vitamin D, riboflavin, vitamin B 12, and vitamin A ), iodine , and n-3 fatty acids. The 2003 vegetarian food guide recommends that ovolactovegetarians over 50 years of age should take supplements of vitamin B12 and vitamin D, or use foods fortified with these nutrients. Vitamin D supplements are particularly important for older vegetarians living in northern latitudes or other situations in which they receive little sun exposure.

In addition to nutritional concerns, there is some evidence that ovolactovegetarian diets may actually increase the risk of breast cancer in women, particularly in those with lactose intolerance who use large amounts of soy-based products as milk replacements. Soybeans contain phytoestrogens, or plant estrogens, which have been implicated in breast cancer. The plant estrogens in soy-based products may also explain why vegetarians have a disproportionate number of female babies, and why these girls have a higher rate of precocious puberty than girls born to nonvegetarian mothers.

Some researchers think that an ovolactovegetarian diet may delay physical maturation in girls. A study done in California in the early 1990s reported that girls using the Seventh-day Adventist diet were less tall prior to adolescence than their age-matched nonvegetarian counterparts. Further research in this field is necessary, however.

Ovolactovegetarianism may also be less beneficial than ovovegetarianism to maintaining fertility in women of childbearing age. A group of researchers at the Harvard School of Public Health reported in early 2007 that a high intake of low-fat dairy foods is associated with infertility in women caused by failure to ovulate.

Research and general acceptance

General acceptance

Vegetarianism in general is accepted by all mainstream medical associations and professional nutritionists’ societies, and positively recommended by some. The position statement jointly adopted by the ADA and DC in 2003 states: ‘It is the position of the American Dietetic Association and Dietitians of Canada that appropriately planned vegetarian diets are healthful, nutritionally adequate and provide health benefits in the prevention and treatment of certain diseases. . . . 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.’

The ADA 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 ADA for an annual subscription fee of $25. The Vegetarian Nutrition DPG also has its own website at http://www.vegetariannutrition.net/index.htm with articles available to the public on vegetarian diets and cancer prevention, treatment of rheumatoid arthritis, sports nutrition , and pregnancy. Most of these articles assume that readers are ovolactovegetarians.

Once considered an eccentricity, ovolactovegetarianism 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 presently offer ovolactovegetarian dishes as a matter of course. The ADA and DC state that about 2.5% of adults (defined as people over 18 years of age) in the United States and 4% of Canadian adults follow some type of vegetarian diet. The Vegetarian Resource Group (VRG), a nonprofit research organization, conducted a poll in 2006. It estimated that 2.3% of adults in the United States— 4.7 million people—are vegetarians, with half to two-thirds of this group being ovolactovegetarians. In addition, the VRG notes that 30 to 40% of American adults choose vegetarian dishes over meat dishes at least some of the time.

Most of the opposition in developed countries to ovolactovegetarians is within vegetarian societies or groups rather than between this subgroup of vegetarians and nonvegetarians. Vegans in particular are likely to regard ovolactovegetarians as ethically less ‘pure,’ as veganism itself was started in the 1940s by an Englishman who was frustrated by the fact that most of the vegetarians he knew saw nothing morally wrong with consuming eggs or dairy products. One registered dietitian who offers tutorials on vegetarian nutrition and food service has remarked, ‘This [definition of a proper vegetarian] is a very hot topic for some people, who are adamant that their definitions or life-style choices are the only way. For the sake of these lectures, it will be easier for those people . . . with very strong feelings to park their dogma by the door.’


Most of the research in nutrition and medicine that has been carried out on vegetarians in the West has been done with research subjects who are ovolactovegetarians, with a smaller number of studies done on vegans. In general, Western researchers use ‘vegetarians’ simply speaking as a synonym for ovolactovegetarians. Most studies done in India, however, have recruited lactovegetarian subjects, as strict Hindus do not eat eggs. As a result, it is not always easy to compare study findings from different countries unless the subjects were drawn from the same vegetarian subgroup. It is interesting to note that a recent study of French vegetarians used the term ‘classical vegetarians’ to distinguish ovolactovegetarian subjects from those who were following lactovegetarian or macrobiotic diets.

As has been noted in Europe as well as the United States, the emphasis in medical research on all types of vegetarian diets has shifted in the early 2000s 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 ovolactovegetarian diets lower the risk of heart disease, stroke, and type 2 diabetes. The Adventist Health Study received new funding in 2003 for its continuation. As of early 2007, the NIH is conducting five additional clinical trials to evaluate the advantages of ovolactovegetarian diets in managing uremia in the elderly, cardiovascular disease, type 2 diabetes, high blood pressure, and postmenopausal disorders in women as well as treating obesity.

European studies of ovolactovegetarians often focus on regional diets—such as the health benefits of eliminating meat and fish from Mediterranean diets. In addition, as of 2007 there is an ongoing major European study of the associations between dietary intake and cancer risk known as the European Prospective Investigation into Cancer and Nutrition (EPIC). EPIC recruited over 521,000 healthy adults between the ages of 35 and 70 in 10 European countries between 1993 and 1999, with follow-ups scheduled through 2009 and possibly longer. One subcategory in the EPIC study is a cohort of 27,000 vegetarians and vegans in the United Kingdom—the largest single subgroup in the EPIC study. It is expected that the very high levels of phytoestrogens (5 to 50 times higher than in those in nonvegetarian European subjects) in the blood plasma of the British vegetarians will provide further information about the long-term effects of ovolactovegetarian as well as vegan diets.



Colbert, Don. What Would Jesus Eat? Nashville, TN: T. Nelson Publishers, 2002. A conservative Christian attempt to prove that Jesus was a vegetarian.

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Pelletier, Kenneth R., MD. The Best Alternative Medicine, Chapter 3, ‘Food for Thought.’ New York: Fireside Books, 2002. A good summary of recent studies of the health benefits of ovolactovegetarianism.

Scully, Matthew. Dominion: The Power of Man, the Suffering of Animals, and the Call to Mercy. New York: St. Martin’s Press, 2002. The author’s focus is on kindness to animals rather than vegetarianism in the strict sense; however, he has been a vegetarian since the late 1970s, and his chapters on commercialized hunting, fishing, and factory farming are of particular interest to vegetarians.

Stuart, Tristan. The Bloodless Revolution: A Cultural History of Vegetarianism from 1600 to Modern Times. New York: W. W. Norton & Co., 2006.


Brill, Steve (‘Wildman’). The Wild Vegetarian Cookbook: A Forager’s Culinary Guide. Boston: Harvard Common Press, 2002.

Colbert, Don. The What Would Jesus Eat? Cookbook. Nashville, TN: Thomas Nelson Publishers, 2002.

Katzen, Mollie. The New Moosewood Cookbook. Berkeley, CA: Ten Speed Press, 2000. A favorite with several generations of young adults.

Nowakowski, John B. Vegetarian Magic at the Regency House Spa. Summertown, TN: Book Pub., 2000.


American Dietetic Association and Dietitians of Canada. ‘Position of the American Dietetic Association and Dietitians of Canada: Vegetarian Diets.’ Canadian Journal of Dietetic Practice and Research 64 (Summer 2003): 62–81.

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Sabate, J., M. C. Llorca, and A. Sanchez. ‘Lower Height of Lacto-ovovegetarian Girls at Preadolescence: An Indicator of Physical Maturation Delay?’ Journal of the American Dietetic Association 92 (October 1992): 1263–1264.

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American Dietetic Association (ADA) fact sheet. Calcium and Vitamin D: Essential Nutrients for Bone Health. Chicago, IL: ADA, 2006. Available online in PDF format at http://www.eatright.org/ada/files/Tropicana_Fact_Sheet.pdf.

American Dietetic Association (ADA) fact sheet. Healthy Weight with Dairy. Chicago, IL: ADA, 2004. Available online in PDF format at http://www.eatright.org/ada/files/04_HealthyChoice_NDC_fin.pdf.

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North American Vegetarian Society (NAVS). Vegetarianism: Answers to the Most Commonly Asked Questions. Dolgeville, NY: NAVS, 2005. Available online at http://www.navs-online.org/frvegetarianism.html.

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American Dietetic Association (ADA). 120 South Riverside Plaza, Suite 2000, Chicago, IL 60606-6995. Telephone: (800): 877-1600. Website: http://www.eatright.org.

Dietitians of Canada/Les dietetistes du Canada (DC). 480 University Avenue, Suite 604, Toronto, Ontario, Canada M5G 1V2. Telephone: (416) 596-0857. Website: http://www.dietitians.ca.

North American Vegetarian Society (NAVS). P.O. Box 72, Dolgeville, NY 13329. Telephone: (518) 568-7970. Website: http://www.navs-online.org.

Seventh-day Adventist Dietetic Association (SDADA). 9355 Telfer Run, Orlando, FL 32817. Website: http://www.sdada.org. SDADA is an official affiliate of the ADA.

Vegetarian Resource Group (VRG). P.O. Box 1463, Dept. IN, Baltimore, MD 21203. Telephone: (410) 366-VEGE. Website: http://www.vrg.org/index.htm. Publishes Vegetarian Journal, a quarterly periodical.

Rebecca J. Frey, PhD