Position of the American Dietetic Association:
A considerable body of scientific data suggests positive relationships between vegetarian diets and risk reduction for several chronic degenerative diseases and conditions, including obesity, coronary artery disease, hypertension, diabetes mellitus and some types of cancer.
It is the position of The American Dietetic Association that vegetarian diets are healthful and nutritionally adequate when appropriately planned.
Vegetarianism in perspective
There is no single vegetarian eating pattern. The vegetarian diet is mainly plant foods: fruits, vegetables, legumes, grains, seeds, and nuts. Eggs, dairy products, or both may be included as well. The lactovegetarian diet is fruits, vegetables, grains, dairy foods, and their products whereas the lacto-ovovegetarian diet also adds eggs. The vegan, or total vegetarian, diet completely excludes meat, fish, fowl, eggs, and dairy products. Even within specific classifications of the diet, considerable variation may exist in the extent to which animal products are avoided. Therefore, individual assessment is required in order to accurately evaluate the nutritional quality of a given diet.
Studies of vegetarians indicate that they often have lower mortality rates from several chronic degenerative diseases than do nonvegetarians (1,2). These effects may be attributable to diet as well as to other lifestyle characteristics such as maintaining desirable weight, regular physical activity, and abstinence from smoking, alcohol, and illicit drugs.
In addition to possible health advantages, other considerations that may lead to the adoption of a vegetarian diet include environmental or ecological concerns, world hunger issues, economic reasons, philosophical or ethical reasons, and religious beliefs.
Implications for health promotion
Mortality from coronary artery disease is lower in vegetarians than in nonvegetarians (1,2). Total serum cholesterol and low-density lipoprotein cholesterol levels are usually lower, whereas high density lipoprotein cholesterol and triglyceride levels vary, depending on the type of vegetarian diet followed (3,4). Low-fat, low-cholesterol vegetarian diets may decrease levels of apoprotein A, B, and E; alter platelet composition and platelet function; and decrease plasma viscosity. One study demonstrated reversal of even severe coronary artery disease without the use of lipid lowering drugs by using a combination of a vegetarian diet deriving less than 10% of its energy from fat, smoking cessation, stress management, and moderate exercise (3). Vegetarians have lower rates of hypertension (5) and non-insulin-dependent diabetes mellitus than do nonvegetarians; lessening these risk factors may also decrease the risk of cardiovascular and coronary artery disease in the vegetarian population.
Seventh-Day Adventist vegetarians have lower rates of mortality from colon cancer than the general population (6). This may be attributable to dietary differences that include increased fiber intake; decreased intake of total fat, saturated fat, cholesterol, and caffeine; increased intake of fruits and vegetables; and, in lactovegetarians, increased intakes of calcium. The dietary differences, especially in vegans, may produce physiologic changes that may inhibit the causal chain for colon cancer (7). Reduced consumption of meat and animal protein has also been associated with decreased colon cancer in some, but not all, studies of omnivores. Lung cancer rates are lower in vegetarians, chiefly because they usually do not smoke, but possibly also because of diet (8). Research suggests that vegetarians are also at decreased risk for breast cancer (9).
Obesity, a major public health problem in the United States, exacerbates or complicates many diseases. Vegetarians, especially vegans, often have weights that are closer to desirable weights than do nonvegetarians (10).
Vegetarians may be at lower risk for non-insulin-dependent diabetes because they are leaner than nonvegetarians. Also, vegetarians' high intake of complex carbohydrates, which are often relatively high in fiber content, improves carbohydrate metabolism and may lower basal blood glucose levels (11).
Plant sources of protein alone can provide adequate amounts of the essential and nonessential amino adds, assuming that dietary protein sources from plants are reasonably varied and that caloric intake is sufficient to meet energy needs. Whole grains, legumes, vegetables, seeds, and nuts all contain essential and nonessential amino acids.
Conscious combining of these foods within a given meal, as the complementary protein dictum suggests, is unnecessary. Additionally, soy protein has been shown to be nutritionally equivalent in protein value to proteins of animal origin and, thus, can serve as the sole source of protein intake if desired (12).
Although most vegetarian diets meet or exceed the Recommended Dietary Allowances (13) for protein, they often provide less protein than nonvegetarian diets. This lower protein intake may be associated with better calcium retention in vegetarians and improved kidney function in individuals with prior kidney damage. Further, lower protein intakes may result in a lower fat intake with its inherent advantages, because foods high in protein are frequently high in fat also.
Suggested daily servings
Breads, cereals, rice and pasta
6 or more
1 slice bread
1/2 bun, bagel, or bread roll
1/2 cup cooked cereal, rice, or pasta
1 oz dry cereal
4 or more
1/2 cup cooked or 1 cup raw
Legumes and other meat substitutes
2 to 3
1/2 cup cooked beans
4 oz tofu or tempeh
8 oz soy milk
2 Tbsp nuts or seeds (these tend to be high in fat, so use sparingly if you are following a low-fat diet)
3 or more
1 piece fresh fruit
3/4 cup fruit juice
1/2 cup canned or cooked fruit
Optional- up 1 to 3 servings daily
1 cup low-fat or skim milk
1 cup low-fat or nonfat yogurt
1 1/2 oz low-fat cheese
Optional - limit to 3 to 4 yolks per week
1 egg or 2 egg whites
Fats, sweets, alcohol and beverages
Go easy on these foods
Oil, margarine, and mayonnaise
Cakes, cookies, pies, pastries and candies
Beer, wine, and spirits
Daily food guide for vegetarians. Source: Eating Well --The Vegetarian
Way. Chicago, Ill: American Dietetic Association; 1992.
Plant carbohydrates are usually accompanied by liberal amounts of dietary fiber. This is in contrast to animal products, which are devoid of fiber. Fiber has been shown to be important in the prevention and treatment of certain conditions and diseases.
Vegetarian diets that are low in animal products are typically lower than nonvegetarian diets in total fat, saturated fat, and cholesterol, factors associated with reduced risk of coronary artery disease and some forms of cancer.
Adequate iron nutriture depends on both the amount of dietary iron consumed and the amount absorbed. Inhibitors and enhancers affect the absorption of nonhaem iron, the form of iron found in plants. However, inhibitors and enhancers can offset each other when a variety of foods is consumed. Vegetarians are not at greater risk of iron deficiency than nonvegetarians, but Western vegetarians generally have better iron status than those in developing countries. Western vegetarians generally have an adequate intake of iron from plant products. They also consume greater amounts of ascorbic acid, an important enhancer of nonhaem iron absorption. In contrast, vegetarians in developing countries rely on food staples that are low in iron; consume less ascorbic acid; and consume more tea, which contains tannin, an inhibitor of iron absorption.
The Recommended Dietary Allowance (13) for vitamin B-12 is minute. Vitamin B-12 is produced by microorganisms present in the guts or gastrointestinal tracts of animals and human beings, as well as in dirt on the surface of unwashed plants. Vitamin B-12 is found in all animal products; hence, a pattern that includes animal products such as milk and milk products is unlikely to be deficient in vitamin B-12. Bacteria produce vitamin B-12 in the human gut, but it appears to be produced beyond the ileum, the site of vitamin B-12 absorption in the intestine (14).
Lack of intrinsic factor in the stomach, rather than diet, however, is the most common cause of vitamin B-12 deficiency. Atrophic gastritis, with the consequent bacterial overgrowth of the upper gut, may also contribute to vitamin B-12 deficiency, especially in the elderly. Plants provide no vitamin B-12. In countries where sanitation is poor, vegans may derive vitamin B-12 from foods that are contaminated with microbes and organisms that produce the vitamin, such as on the surfaces of unwashed fruits or vegetables. In Western countries, however, where sanitary practices are better, the risk of vitamin B-12 deficiency for vegans may be greater.
Vegans should include a reliable source of the vitamin in their diets. Spirulina, seaweed, tempeh, and other fermented foods are not reliable sources of vitamin B-12. As much as 80% to 94% of the so-called vitamin B-12 in these foods, as measured by microbiological assay, may be inactive analogs. Cyanocobalamin, the form of vitamin B-12 that is physiologically active for human beings, is available from vitamin supplements or fortified foods such as some commercial breakfast cereals, soy beverages, some brands of nutritional yeast, and other products.
Certain plant constituents appear to inhibit the absorption of dietary calcium, but within the context of the total diet, this effect does not appear to be significant. Calcium from low-oxalate vegetable greens, such as kale, has been shown to be absorbed as well or better than calcium from cow's milk (15). Calcium deficiency in vegetarians is rare, and there is little evidence to show that calcium intakes below the Recommended Dietary Allowance (13) cause major health problems in the vegetarian population. The relatively high US recommendations for calcium intake, compared with those for populations consuming a more plant based diet, are designed to compensate for the calciuric effect of high intakes of animal protein, which are customary in the United States. Studies have shown that vegetarians, on the other hand, absorb and retain more calcium from foods than do nonvegetarians (16,17).
Zinc is necessary for proper growth and development. Good plant sources include grains, nuts and legumes. Western vegetarians usually have satisfactory zinc status (18).
Groups with special needs
Infants, children, and adolescents who consume well-planned vegetarian diets can generally meet all of their nutritional requirements for growth (19,20). Those who follow vegan or veganlike diets should consume a reliable source of vitamin B-12 and should have a reliable source of vitamin D. Calcium, iron, and zinc intakes may also deserve special attention, although intakes are usually adequate when reasonable variety and adequate energy are consumed.
If exposure to sunlight is limited, the need for vitamin D supplementation should be assessed. Because vegan diets tend to be high in bulk, care should be taken to ensure that caloric intakes are sufficient to meet energy needs, particularly in infancy and during weaning. Both vegetarians and nonvegetarians whose infants are premature or solely breastfed beyond 4 to 6 months of age should provide supplements of vitamin D, if exposure to sunlight is inadequate, and iron from birth or at least by 4 to 6 months of age (21).
Well-planned vegetarian diets can be adequate for pregnant and lactating women. Vegetarians and nonvegetarians alike are generally advised to take iron and folic acid supplements during pregnancy, although vegetarians frequently have greater intakes of those nutrients than do nonvegetarians. A regular source of vitamin B-12 is recommended for vegans during pregnancy and lactation (21,22). A vitamin D supplement should be taken by pregnant and lactating vegans if exposure to sunlight is inadequate. Consumption of a variety of foods and adequate energy will help ensure adequate intakes of calcium, iron, and zinc.
In planning vegetarian diets of any type, one should choose a wide variety of foods and ensure that the caloric intake is adequate to meet energy needs (23). (See the Figure.) Additionally, the following recommendations are in order.
* Keep the intake of low nutrient-dense foods, such as sweets and fatty foods, to a minimum. -- Choose whole or unrefined grain products, instead of refined products, whenever possible, or use fortified or enriched cereal products.
* Use a variety of fruits and vegetables, including a good food source of vitamin C.
* If milk or dairy products are consumed, use low-fat or nonfat varieties.
* Limit egg intake to 3 to 4 yolks per week.
* Vegans should have a reliable source of vitamin B-12, such as some fortified commercial breakfast cereals, fortified soy beverages, or a cyanocobalamin supplement. A vitamin D supplement may be indicated if exposure to sunlight is limited.
* Vegetarian and nonvegetarian infants who are solely breastfed beyond 4 to 6 months of age should receive supplements of iron and vitamin D if exposure to sunlight is limited.
The Dietary Guidelines for Americans (24) recommend a reduction in fat intake and an increased consumption of fruits, vegetables, and whole grains. Well-planned vegetarian diets can effectively meet these guidelines and can be a health-supporting dietary alternative.
1. Burr ML, Butland BK. Heart disease in British vegetarians. Am J Clin Nutr. 1988; 48:830-832.
2. Fraser GE. Determinants of ischemic heart disease in Seventh-Day Adventists: a review. Am J Clin Nutr. 1988;48:833-836.
3. Ornish D, Brown S, Scherwitz L, Billings J, Armstrong W, Ports T, McLanahan S, Kirkeeide R, Brand R, Gould KL. Can lifestyle changes reverse coronary heart disease? Lancet. 1990;336:129-133.
4. Kestin M, Rouse I, Correll R, Nestel P. Cardiovascular disease risk factors in free-living men: comparison of two prudent diets, one based on lactoovovegetarianism and the other allowing lean meat. Am J Clin Nutr. 1989;50:280-287.
5. Beilin, LJ, Rouse IL, Armstrong BK, Margetts BM, Vandongen R. Vegetarian diet and blood pressure levels: incidental or causal association? Am J Clin Nutr. 1988;48:806-810.
6. Phillips R, Snowdon D. Association of meat and coffee use with cancers of the large bowel, breast, and prostate among Seventh-Day Adventists: preliminary results. Cancer Res. 1983;45 (suppl):2403-2408.
7. Turjiman N, Goodman GT, Jaeger B, Nair PP. Diet, nutrition intake and metabolism in populations at high and low risk for colon cancer: metabolism of bile acids. Am J Clin Nutr. 1984;4:937.
8. Colditz G, Stampfer M, Willet W. Diet and lung cancer: a review of the epidemiological evidence in humans. Arch Intern Med. 1987;147:157.
9. Chen J, Campbell TC, Li J, Peto R. In: Diet, Life-style and Mortality in China. A study of the characteristics of 65 Counties. Oxford University Press, Cornell University Press, and the China People's Medical Publishing House; 1990.
10. Bergan JC, Brown PT. Nutritional status of "new" vegetarians. J Am Diet Assoc. 1980;76:151-155.
11. Nieman DC, Underwood BC, Sherman KM, Arabatzis K, Barbosa JC, Johnson M, Shultz TD. Dietary status of Seventh-Day Adventist vegetarian and non-vegetarian elderly women. J Am Diet Assoc. 1989;89:1763-1769.
12. Young VR. Soy protein in relation to human protein and amino acid nutrition. J Am Diet Assoc. 1991;91:828-835.
13. Food and Nutrition Board. Recommended Dietary Allowances. 10th ed. Washington, DC: National Academy Press; 1989.
14. Herbert V. Vitamin B-12: plant sources, requirements, assay. In: Mutch PB, Johnston PK, eds. First International Congress on Vegetarian Nutrition. Am J Clin Nutr. 1988; 48:452.
15. Heaney R, Weaver C. Calcium absorption from kale. Am J Clin Nutr. 1990;51:656.
16. Zemel M. Calcium utilization: effect of varying level and source of dietary protein. Am J Clin Nutr. 1988;48:880.
17. Marsh A, Sanchez T, Michelsen O, Chaffee F, Fagal S. Vegetarian lifestyle and bone mineral density. Am J Clin Nutr. 1988;48:837-841.
18. Hambige K, Casey C, Krebs N. Zinc. In: Mertz W, ed. Trace Elements in Human and Animal Nutrition. Vol 2. 5th ed. Orlando, Fla: Academic Press; 1986.
19. Sabate J, Lindsted K, Harris R. Sanchez A. Attained height of lacto-ovo vegetarian children and adolescents. Eur J Clin Nutr. 1991;45:51-58.
20. O'Connell J, Dibley M, Sierra J, Wallace B, Marks J, Yip R. Growth of vegetarian children: the Farm study. Pediatrics. 1989;84:475-480.
21. Food and Nutrition Board, Institute of Medicine. Nutrition During Lactation. Washington, DC: National Academy Press; 1991.
22. Food and Nutrition Board, Institute of Medicine. Nutrition During Pregnancy. Washington, DC: National Academy Press; 1991.
23. Eating Well--The Vegetarian Way. Chicago, Ill: American Dietetic Association; 1992.
24. Nutrition and Your Health: Dietary Guidelines for Americans. 3rd ed. Washington, DC: US Dept of Agriculture and US Dept of Health and Human Services; 1990.
* ADA Position adopted by the House of Delegates on October 18, 1987 and reaffirmed on September 12, 1992. The update will be in effect until October 1997.
* Recognition is given to the following for their contributions:
Suzanne Havala, MS, RD; Johanna Dwyer, DSc, RD
Phyllis Acosta, RD; Patricia Johnston, DrPH, RD; Mary Clifford, RD; Vegetarian Nutrition dietetic practice group: Winston Craig, PhD, RD, and Virginia Messina, MPH, RD; Pediatric Nutrition dietetic practice group
This position paper was "reprinted" from Journal of the American
Dietetic Association, November 1993, Volume 93, Number 11.