Position of The American Dietetic Association: Vegetarian diets

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Position of The American Dietetic Association: Vegetarian diets

 

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Position of The American Dietetic Association:

Vegetarian diets

 

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.

 

Position Statement

 

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 apoproteins 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).

 

Nutrition Considerations

 

Plant sources of protein alone can provide adequate amounts

of the essential and nonessential amino acids, assuming that

dietary protein sources from plants are reasonably varied and

that caloric intake is sufficient to fulfill 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.

 

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

nonheme 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

nonheme 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 as 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

 

nonvegetar-ians (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 fulfill

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

satisfy 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.

 

Meal Planning

 

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 fulfill these

guidelines and can be a health-supporting dietary alternative.

 

 

References

 

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. The American Dietetic Association authorizes republication

of the position, in its entirety, provided full and proper credit is given.

Recognition is given to the following for their contributions:

Authors:

Suzanne Havala, MS, RD; Johanna Dwyer, DSc, RD

Reviewers:

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

 

 

 

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