• Volume 103
• Number 6
Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets
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. Approximately 2.5% of adults in the
United States and 4% of adults in Canada follow vegetarian diets. A
vegetarian diet is defined as one that does not include meat, fish, or
fowl. Interest in vegetarianism appears to be increasing, with many
restaurants and college foodservices offering vegetarian meals
routinely. Substantial growth in sales of foods attractive to
vegetarians has occurred, and these foods appear in many supermarkets.
This position paper reviews the current scientific data related to key
nutrients for vegetarians, including protein, iron, zinc, calcium,
vitamin D, riboflavin, vitamin B-12, vitamin A, n-3 fatty acids, and
iodine. A vegetarian, including vegan, diet can meet current
recommendations for all of these nutrients. In some cases, use of
fortified foods or supplements can be helpful in meeting
recommendations for individual nutrients. 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. Vegetarian diets offer a number of nutritional benefits,
including lower levels of saturated fat, cholesterol, and animal
protein as well as higher levels of carbohydrates, fiber, magnesium,
potassium, folate, and antioxidants such as vitamins C and E and
phytochemicals. Vegetarians have been reported to have lower body mass
indices than nonvegetarians, as well as lower rates of death from
ischemic heart disease; vegetarians also show lower blood cholesterol
levels; lower blood pressure; and lower rates of hypertension, type 2
diabetes, and prostate and colon cancer. Although a number of federally
funded and institutional feeding programs can accommodate vegetarians,
few have foods suitable for vegans at this time. Because of the
variability of dietary practices among vegetarians, individual
assessment of dietary intakes of vegetarians is required. Dietetics
professionals have a responsibility to support and encourage those who
express an interest in consuming a vegetarian diet. They can play key
roles in educating vegetarian clients about food sources of specific
nutrients, food purchase and preparation, and any dietary modifications
that may be necessary to meet individual needs. Menu planning for
vegetarians can be simplified by use of a food guide that specifies
food groups and serving sizes. J Am Diet Assoc. 2003;103:748-765.
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.
A vegetarian is a
person who does not eat meat, fish, or fowl or products containing
these foods. The eating patterns of vegetarians may vary considerably.
The lacto-ovo-vegetarian eating pattern is based on grains, vegetables,
fruits, legumes, seeds, nuts, dairy products, and eggs but excludes
meat, fish, and fowl. The lacto-vegetarian excludes eggs as well as
meat, fish, and fowl. The vegan, or total vegetarian, eating pattern is
similar to the lacto-vegetarian pattern, with the additional exclusion
of dairy and other animal products. Even within these patterns,
considerable variation may exist in the extent to which animal products
People choosing macrobiotic diets are frequently identified
as following a vegetarian diet. The macrobiotic diet is based largely
on grains, legumes, and vegetables. Fruits, nuts, and seeds are used to
a lesser extent. Some people following a macrobiotic diet are not truly
vegetarian because they use limited amounts of fish. Some
“self-described” vegetarians, who are not vegetarians at all, will eat
fish, chicken, or even meat (1,2).
Some research studies have identified these “self-described”
vegetarians as semivegetarians and have defined semivegetarian as
occasional meat eaters who predominately practice a vegetarian diet (3) or those who eat fish and poultry but less than 1 time per week (4).
Individual assessment is required to accurately evaluate the
nutritional quality of the diet of a vegetarian or someone who says
that they are vegetarian.
Common reasons for choosing a vegetarian diet include health
considerations, concern for the environment, and animal welfare factors
Vegetarians also cite economic reasons, ethical considerations, world
hunger issues, and religious beliefs as their reasons for following
their chosen eating pattern.
In 2000, approximately 2.5% of the US adult population (4.8 million
people) consistently followed a vegetarian diet and affirmed that they
never ate meat, fish, or poultry (7). Slightly less than 1% of those polled were vegans (7).
According to this poll, vegetarians are most likely to live on the east
or west coast, in large cities, and to be female. Approximately 2% of
6- to 17-year-old children and adolescents in the United States are
vegetarians, and around 0.5% of this age group are vegan (8). According to a 2002 survey (9),
about 4% of Canadian adults are vegetarian; this represents an
estimated 900,000 people. Factors that may affect the number of
vegetarians in the United States and Canada in the future include an
increased interest in vegetarianism and the arrival of immigrants from
countries where vegetarianism is commonly practiced (10).
Twenty to 25% of adults in the United States report that they eat 4 or
more meatless meals weekly or “usually or sometimes maintain a
vegetarian diet,” suggesting an interest in vegetarianism (11).
Additional evidence for the increased interest in vegetarianism
includes the emergence of animal rights/ethics courses on college and
university campuses; the proliferation of Web sites, magazines and
newsletters, and cookbooks with a vegetarian theme; and the public's
attitude toward ordering a vegetarian meal when eating away from home.
More than 5% of those surveyed in 1999 said they always order a
vegetarian meal when they eat out; close to 60% “sometimes, often, or
always” order a vegetarian item at a restaurant (12).
Restaurants have responded to this interest in vegetarianism.
The National Restaurant Association reports that 8 out of 10
restaurants in the United States with table service offer vegetarian
entrees (13). Fast-food
restaurants are beginning to offer salads, veggie burgers, and other
vegetarian options. Many college students consider themselves
vegetarians. In response to this, most university foodservices offer
vegetarian options (14).
There has also been a growth in professional interest in
vegetarian nutrition; the number of articles in the scientific
literature related to vegetarianism has increased from less than 10
articles per year in the late 1960s to 76 articles per year in the
1990s (15). In addition,
the main focus of the articles is changing. Twenty-five or more years
ago, articles primarily had themes questioning the nutritional adequacy
of vegetarian diets. More recently, the theme has been the use of
vegetarian diets in the prevention and treatment of disease. More
articles feature epidemiological studies, and fewer reports are case
studies and letters to the editor (15).
There is a growing appreciation for the benefits of plant-based
diets, defined as diets that include generous amounts of plant foods
and limited amounts of animal foods. The American Institute for Cancer
Research and the World Cancer Research Fund call for choosing
predominantly plant-based diets rich in a variety of vegetables and
fruits, legumes, and minimally processed starchy staple foods and
limiting red meat consumption, if red meat is eaten at all (16). The American Cancer Society recommends choosing most food from plant sources (17). The American Heart Association recommends choosing a balanced diet with an emphasis on vegetables, grains, and fruits (18),
and the Heart and Stroke Foundation of Canada recommends using grains
and vegetables instead of meat as the centerpiece of meals (19).
The Unified Dietary Guidelines developed by the American Cancer
Society, the American Heart Association, the National Institutes of
Health, and the American Academy of Pediatrics call for a diet based on
a variety of plant foods, including grain products, vegetables, and
fruits to reduce risk of major chronic diseases (20).
New product availability
The US market for vegetarian foods (foods like meat analogs,
nondairy milks, and vegetarian entrees that directly replace meat or
other animal products) was estimated to be $1.5 billion in 2002, up
from $310 million in 1996 (21). This market is expected to nearly double by 2006 to $2.8 billion (21). Canadian sales of meat analogs more than tripled between 1997 and 2001 (22).
The ready availability of new products, including fortified
foods and convenience foods would be expected to have a marked impact
on nutrient intake of vegetarians. Fortified foods such as soymilks,
meat analogs, juices, and breakfast cereals can add substantially to
vegetarians' intakes of calcium, iron, zinc, vitamin B-12, vitamin D,
and riboflavin. Vegetarian convenience foods including veggie burgers
and veggie dogs, frozen entrees, meals in a cup, and soymilk can make
it much simpler to be a vegetarian today than in the past.
Vegetarian foods are readily available, both in supermarkets
and in natural foods stores. About half of vegetarian foods volume is
sold through supermarkets and about half through natural foods stores (21). Three-fourths of soymilk sales take place in supermarkets (21).
Public policy statements and vegetarian diets
The United States Dietary Guidelines (23) state, “Vegetarian diets can be consistent with the Dietary Guidelines for Americans,
and meet Recommended Dietary Allowances for nutrients.” They give
recommendations on meeting nutrient requirements for those who choose
to avoid all or most animal products. Some have said that
implementation of the Dietary Guidelines can best be achieved by use of
vegetarian and plant-rich diets (24).
National food guides include some vegetarian options. Foods commonly
eaten by vegetarians such as legumes, tofu, soyburgers, and soymilk
with added calcium are included in a table accompanying the USDA's Food
Guide Pyramid (23). Canada's Food Guide to Healthy Eating can be used by lacto and lacto-ovo-vegetarians (25). Health Canada has stated that well-planned vegetarian diets are supportive of good nutritional status and health (26).
offer a number of advantages, including lower levels of saturated fat,
cholesterol, and animal protein and higher levels of carbohydrates,
fiber, magnesium, boron, folate, antioxidants such as vitamins C and E,
carotenoids, and phytochemicals (27-30).
Some vegans may have intakes for vitamin B-12, vitamin D, calcium,
zinc, and occasionally riboflavin that are lower than recommended (27,29,31).
Plant protein can meet requirements when a variety of plant foods
is consumed and energy needs are met. Research indicates that an
assortment of plant foods eaten over the course of a day can provide
all essential amino acids and ensure adequate nitrogen retention and
use in healthy adults, thus complementary proteins do not need to be
consumed at the same meal (32).
Estimates of protein requirements of vegans vary, depending to some degree on diet choices (33).
A recent metaanalysis of nitrogen balance studies found no significant
difference in protein needs due to the source of dietary protein (34,35).
Based primarily on the lower digestibility of plant proteins, other
groups have suggested that protein requirements of vegans may be
increased by 30% to 35% for infants up to the age of 2 years, 20% to
30% for 2- to 6-year-old children, and 15% to 20% for those 6 years and
older, in comparison with those of nonvegetarians (36).
The quality of plant proteins varies. Based on the protein
digestibility corrected amino acid score (PDCAAS), which is the
standard method for determining protein quality, isolated soy protein
can meet protein needs as effectively as animal protein, whereas wheat
protein eaten alone, for example, may be 50% less usable than animal
protein (37). Nutrition
care professionals should be aware that protein needs might be higher
than the RDA in vegetarians whose dietary protein sources are mainly
those that are less well digested, such as some cereals and legumes.
Cereals tend to be low in lysine, an essential amino acid.
This may be relevant when evaluating diets of individuals who do not
consume animal protein sources and are relatively low in protein (35).
Dietary adjustments such as the use of more beans and soy products in
place of other protein sources that are lower in lysine or an increase
in dietary protein from all sources can ensure an adequate intake of
Although some vegan women have protein intakes that are
marginal, typical protein intakes of lacto-ovo-vegetarians and of
vegans appear to meet and exceed requirements (29). Athletes can also meet their protein needs on plant-based diets (38,39).
Plant foods contain only nonheme iron, which is more sensitive than
heme iron to both inhibitors and enhancers of iron absorption.
Inhibitors of iron absorption include phytate; calcium; teas, including
some herb teas; coffee; cocoa; some spices; and fiber (40).
Vitamin C and other organic acids found in fruits and vegetables can
enhance iron absorption and can help to reduce effects of phytate (41-43).
Studies show that iron absorption would be significantly reduced if a
diet were to be high in inhibitors and low in enhancers. Recommended
iron intakes for vegetarians are 1.8 times those of nonvegetarians
because of lower bioavailability of iron from a vegetarian diet (44).
The main inhibitor of iron absorption in vegetarian diets is
phytate. Because iron intake increases as phytate intake increases,
effects on iron status are somewhat less than might be expected. Fiber
appears to have a minor effect on iron absorption (45,46). Vitamin C, consumed at the same time as the iron source, can help to reduce the inhibitory effects of phytate (42,43), and some research links high vitamin C intake to improved iron status (47,48). The same is true for organic acids in fruits and vegetables (41). The higher intakes of vitamin C and of vegetables and fruits by vegetarians can favorably impact iron absorption (2). Some food preparation techniques such as soaking and sprouting beans, grains, and seeds can hydrolyze phytate (49-51) and may improve iron absorption (42,51,52). Leavening of breads hydrolyzes phytate and enhances iron absorption (49-51,53,54). Other fermentation processes, such as those used to make soy foods like miso and tempeh, may also make iron more available (55),
although not all research supports this. Whereas many studies of iron
absorption have been short term, there is evidence that adaptation to
low intakes takes place over the longer term and involves both
increased absorption and decreased losses (56,57).
It is likely that iron needs will depend on the make up of the overall
diet and be significantly lower for some vegetarians than for others.
Studies typically show iron intake by vegans to be higher
than that of lacto-ovo-vegetarians and of nonvegetarians, and most
studies show iron intake by lacto-ovo-vegetarians to be higher than
that of nonvegetarians (29). Iron sources are shown in the Table.
Table Vegetarian food sources of nutrients
|Nutrient||Amount per serving|
|Soybeans, cooked, 1/2 c (125 mL)||4.4|
|Soybeans, dry roasted, (soy nuts), 1/4 c (60 mL)||1.7|
|Soymilk 1/2 c (125 mL)||0.4-1.0|
|Tempeh, 1/2 c (83 g)||2.2|
|Tofu, firm, 1/2 c (126 g)||6.6|
|Veggie “meats,” fortified, 1 oz (28 g)||0.5-1.9|
|Legumes (cooked, 1/2 c/125 mL)|
|Baked beans, canned, vegetarian||1.7|
|Chickpeas, garbanzo beans||2.4|
|Great northern beans||1.9|
|Nuts, peanuts, seeds, and their butters|
|Almonds, 1/4 c (60 mL)||1.5|
|Cashews, 1/4 c (60 mL)||2.1|
|Peanut butter, 2 tbsp (30 mL)||0.6|
|Peanuts, dry roast, 1/4 c (60 mL)||0.8|
|Pumpkin and squash seeds, dried, 1/4 c (60 mL)||5.2|
|Sesame tahini, 2 tbsp (30 mL)||2.7|
|Sunflower seeds, toasted, 1/4 c (60 mL)||2.3|
|Breads, cereals, and grains|
|Barley, pearled, cooked, 1/2 c (125 mL)||1.0|
|Cereal, ready-to-eat, fortified, 1 oz (28 g)||2.1-18|
|Cream of Wheat, cooked, 1/2 c (125 mL)||5.1|
|Oatmeal, instant, fortified, cooked, 1/2 c (125 mL)||4.2|
|Oatmeal, regular, quick or instant, cooked, 1/2 c (125 mL)||1.6|
|Quinoa, cooked, 1/2 c (125 mL)||2.1|
|Wheat germ, 2 tbsp (14 g)||0.9|
|Whole wheat or white enriched bread, 1 slice (28 g)||0.9|
|Fruits (dried, 1/4 c/60 mL)|
|Vegetables (cooked, 1/2 c/125 mL unless indicated otherwise)|
|Bok choy (Chinese cabbage, pak choi)||0.9|
|Green or yellow beans||0.8|
|Mung bean sprouts||0.8|
|Potato, baked, with skin, 1 medium (173 g)||2.3|
|Blackstrap molasses, 1 tbsp (15 mL)||3.5|
|Soybeans, cooked, 1/2 c (125 mL)||1.0|
|Soybeans, dry roasted, 1/2 c (60 mL)||2.1|
|Soymilk, 1/2 c (125 mL)||0.3|
|Soymilk, fortified, 1/2 c (125 mL)||0.5-1.0|
|Tempeh, 1/2 c (83 g)||0.9|
|Tofu, firm, 1/2 c (126 g)||1.0|
|Veggie “meats,” fortified, 1 oz (28 g)||1.2-2.3|
|Legumes (cooked, 1/2 c/125 mL)||mg|
|Baked beans, canned, vegetarian||1.8|
|Chickpeas, garbanzo beans||1.3|
|Great northern beans||0.8|
|Nuts, peanuts, seeds, and their butters|
|Almonds, 1/4 c (60 mL)||1.2|
|Cashews, 1/4 c (60 mL)||1.9|
|Peanut butter, 2 tbsp (30 mL)||0.9|
|Peanuts, dry roast, 1/4 c (60 mL)||1.2|
|Pumpkin and squash seeds, dried, 1/4 c (60 mL)||2.6|
|Sesame tahini, 2 tbsp (30 mL)||1.4|
|Sunflower seeds, toasted, 1/4 c (60 mL)||1.8|
|Breads, cereals, and grains|
|Barley, pearled, cooked, 1/2 c (125 mL)||0.6|
|Cereal, ready-to-eat, fortified, 1 oz (28 g)||0.7-15|
|Quinoa, cooked, 1/2 c (125 mL)||0.8|
|Wheat germ, 2 tbsp (14 g)||1.8|
|Whole wheat bread, 1 slice (28 g)||0.5|
|Vegetables (cooked, 1/2 cup/125 mL)|
|Dairy foods and eggs|
|Cow's milk, 1/2 c (125 mL)||0.5|
|Cheddar cheese, 3/4 oz (21 g)||0.7|
|Egg, large, 1 (50 g)||0.5|
|Yogurt, 1/2 c (125 mL)||0.8-1.1|
|Cultured soy yogurt, fortified, 1/2 c (125 mL)||367|
|Soybeans, cooked, 1/2 c (125 mL)||88|
|Soybeans, dry roasted, (soy nuts), 1/4 c (60 mL)||60|
|Soybeans, green, 1/2 c (125 mL)||130|
|Soymilk, fortified, 1/2 c (125 mL)||100-159|
|Tofu, firm, calcium-set, 1/2 c (126 g)||120-430|
|Tempeh, 1/2 c (83 g)||92|
|Legumes (cooked, 1/2 c/125 mL)|
|Chickpeas, garbanzo beans||40|
|Great northern or navy beans||60-64|
|Vegetarian baked beans||64|
|Nuts, seeds and their butters|
|Almonds, 1/4 c (60 mL)||88|
|Almond butter, 2 tbsp (30 mL)||86|
|Sesame tahini, 2 tbsp (30 mL)||128|
|Breads, cereals, and grains|
|Cereal, ready-to-eat, fortified, 1 oz (28 g)||55-315|
|Figs, dried, 5||137|
|Orange, 1 large||74|
|Orange juice, fortified, 1/2 c (125 mL)||150|
|Vegetables (cooked, 1 c/250 mL)|
|Bok choy (Chinese cabbage, pak choi)||167-188|
|Blackstrap molasses, 1 tbsp (15 mL)||172|
|Cow's milk, 1/2 c (125 mL)||137-158|
|Cheddar cheese, 3/4 oz (21 g)||153|
|Yogurt, plain, 1/2 c (125 mL)||137-230|
|Cereals, ready-to-eat, fortified, 1 oz (28 g)||0.5-1|
|Egg yolk, large, 1 (17 g)||0.6|
|Cow's milk, fortified, 1/2 c (125 mL)||1.2-1.3|
|Soymilk or other nondairy milk, fortified, 1/2 c (125 mL)||0.5-1.5|
|Almonds, 1/4 c (60 mL)||0.3|
|Cereal, ready-to-eat, fortified, 1 oz (28 g)||0.2-1.7|
|Cow's milk, whole, 2% or skim, 1/2 c (125 mL)||0.2|
|Yogurt, 1/2 c (125 mL)||0.3|
|Egg, large, 1 (50 g)||0.6|
|Mushrooms, cooked, 1/2 c (125 mL)||0.2|
|Nutritional yeast miniflakes, 1 tbsp (3 g)||1.9|
|Soymilk, fortified, 1/2 c (125 mL)||0.2|
|Cereals, ready-to-eat, fortified, 1 oz (28 g)||0.6-6.0|
|Cow's milk, 1/2 c (125 mL)||0.4-0.5|
|Egg, large, 1 (50 g)||0.5|
|Nutritional yeast (Red Star Vegetarian Support Formula), miniflakes, 1 tbsp (3 g)||1.5|
|Soymilk or other nondairy milks, fortified, 1/2 c (125 mL)||0.4-1.6|
|Veggie “meats,” fortified, 1 oz (28 g)||0.5-1.2|
|Canola oil, 1 tbsp (15 mL)||1.3-1.6|
|Flaxseed, ground, 1 tbsp (15 mL)||1.9-2.2|
|Flaxseed oil, 1 tsp (5 mL)||2.7|
|Soybean oil, 1 tbsp (15 mL)||0.9|
|Soybeans, cooked, 1/2 c (125 mL)||1.0|
|Tofu, 1/2 c (126 g)||0.7|
|Walnuts, 1/4 c (60 mL)||2.7|
|Walnut oil, 1 tbsp (15 mL)||1.4-1.7|
Sources: Package information and data from US Department of
Agriculture, Agricultural Research Service, 2002; USDA Nutrient
Database for Standard Reference, Release 15; Nutrient Data Laboratory
Home Page, http://www.nal.usda.gov/fnic/foodcomp;
Bhatty RS. Nutrient composition of whole flaxseed and flaxseed meal.
In: Cunnane SC, Thompson LU, eds. Flaxseed and Human Nutrition.
Champaign, IL: AOCS Press; 1995:22-42.
Incidence of iron deficiency anemia among vegetarians is similar to that of nonvegetarians (29,31,58).
Although vegetarian adults have lower iron stores than nonvegetarians,
their serum ferritin levels are usually within the normal range (58-62).
Because phytate binds zinc, and animal protein is believed to
enhance zinc absorption, total zinc bioavailability appears to be lower
on vegetarian diets (63). Also, some vegetarians have diets that are significantly below recommended intakes for zinc (27,29,64,65).
Although overt zinc deficiency has not been seen in Western
vegetarians, the effects of marginal intakes are poorly understood (66). Zinc requirements for vegetarians whose diets are high in phytate may exceed the RDA (44). Zinc sources are shown in the Table.
Compensatory mechanisms may help vegetarians adapt to lower intakes of zinc (65,67).
Some food preparation techniques, such as soaking and sprouting beans,
grains, and seeds as well as leavening bread, can reduce binding of
zinc by phytate and increase zinc bioavailability (49,50,68).
Calcium is present in many plant foods and fortified foods (see Table).
Low-oxalate greens (bok choy, broccoli, Chinese/Napa cabbage, collards,
kale, okra, turnip greens) provide calcium with high bioavailability
(49% to 61%), in comparison with calcium-set tofu, fortified fruit
juices, and cow's milk (bioavailability in the range of 31% to 32%) and
with fortified soymilk, sesame seeds, almonds, and red and white beans
(bioavailability of 21% to 24%) (69-71).
Figs and soy foods such as cooked soybeans, soy nuts, and tempeh
provide additional calcium. Calcium-fortified foods include fruit
juices, tomato juice, and breakfast cereals. Thus, various food groups
contribute dietary calcium (72,73).
Oxalates present in some foods can greatly reduce calcium absorption,
so vegetables that are very high in these compounds, such as spinach,
beet greens, and Swiss chard, are not good sources of usable calcium
despite their high calcium content. Phytate may also inhibit calcium
absorption. However, some foods with high contents of both phytate and
oxalate, such as soy foods, still provide well-absorbed calcium (71). Factors that enhance calcium absorption include adequate vitamin D and protein.
Calcium intakes of lacto-vegetarians are comparable with or higher than those of nonvegetarians (74,75), whereas intakes of vegans tend to be lower than both groups and often below recommended intakes (27,31,71,75).
Diets high in sulfur-containing amino acids may increase losses of
calcium from bone. Foods with a relatively high ratio of
sulfur-containing amino acids to protein include eggs, meat, fish,
poultry, dairy products, nuts, and many grains. There is some evidence
that the impact of sulfur-containing amino acids is only important with
low calcium intakes. Excessive sodium intake may also promote calcium
losses. In addition, some studies show that the ratio of dietary
calcium to protein is more predictive of bone health than calcium
intake alone. Typically, this ratio is high in lacto-ovo-vegetarian
diets and favors bone health, whereas vegans have a calcium to protein
ratio that is similar to or lower than that of nonvegetarians (71,76).
All vegetarians should meet the recommended intakes for calcium, established for their age group by the Institute of Medicine (77).
This can be accomplished, in nonpregnant, nonlactating adults, by
consuming at least 8 servings per day of foods that provide 10% to 15%
of the Adequate Intake (AI) for calcium, as indicated in the Vegetarian
Food Guide Pyramid and Vegetarian Food Guide Rainbow (72,73). Adjustments for other stages of the life cycle are available (72,73). Many vegans may find that it is easier to meet needs if fortified foods or supplements are included (69-71,78).
Vitamin D status depends on sunlight exposure and intake of vitamin
D fortified foods or supplements. Sun exposure to the face, hands, and
forearms for 5 to 15 minutes per day during the summer at the 42nd
latitude (Boston) is believed to provide sufficient amounts of vitamin
D for light-skinned people (79). Those with dark skin require longer exposure (79).
Sun exposure may be inadequate for those living in Canada and at
northern latitudes in the United States, especially in winter months,
for those in smoggy regions, and for those whose sun exposure is
limited. Furthermore, infants, children, and older adults synthesize
vitamin D less efficiently (77,79,80).
Sunscreen can interfere with vitamin D synthesis, although reports are
inconsistent and may depend on amount of sunscreen applied (79,81,82).
Low vitamin D levels and reduced bone mass have been observed in some
vegan populations at northern latitudes who did not use supplements or
fortified foods, particularly children following macrobiotic diets and
adult Asian vegetarians (29,83-85).
Foods that are fortified with vitamin D include cow's milk,
some brands of soymilk and rice milk, and some breakfast cereals and
margarines (see Table).
Vitamin D3 (cholecalciferol) is of animal origin, whereas vitamin D2
(ergocalciferol) is a form acceptable to vegans. Vitamin D2 may be less
bioavailable than vitamin D3, which could raise the requirements of
vegetarians who depend on D2 supplements to meet vitamin D needs (86). If sun exposure and intake of fortified foods are insufficient, vitamin D supplements are recommended.
Some studies have shown vegans to have lower intakes of riboflavin,
compared with nonvegetarians; however, clinical riboflavin deficiency
has not been observed (27,29,31). In addition to foods shown in the Table,
foods that provide about 1 mg of riboflavin per serving are asparagus,
bananas, beans, broccoli, figs, kale, lentils, peas, seeds, sesame
tahini, sweet potatoes, tofu, tempeh, wheat germ, and enriched bread (87).
Sources of vitamin B-12 that are not derived from animals include
B-12 fortified foods (such as some brands of soymilk, breakfast
cereals, and nutritional yeast) or supplements (see Table).
Unless fortified, no plant food contains significant amounts of active
vitamin B-12. Foods such as sea vegetables and spirulina may contain
vitamin B-12 analogs; neither these nor fermented soy products can be
counted on as reliable sources of active vitamin B-12 (29,88). Lacto-ovo-vegetarians can get adequate vitamin B-12 from dairy foods and eggs if these foods are consumed regularly.
Vegetarian diets are typically high in folic acid, which can
mask the hematological symptoms of vitamin B-12 deficiency. Therefore,
some cases of deficiency may not be detected until after the onset of
neurological symptoms (89).
If there are concerns about vitamin B-12 status, serum homocysteine,
methylmalonic acid, and holotranscobalamin II should be measured (90).
A regular source of vitamin B-12 is crucial for pregnant and
lactating women and for breastfed infants if the mother's diet is not
supplemented. Infants born to vegan mothers whose diets lack reliable
sources of this vitamin are at especially high risk of deficiency.
Maternal vitamin B-12 intake and absorption during pregnancy appear to
have a more important influence on vitamin B-12 status of the infant
than do maternal vitamin B-12 stores (91).
Because 10% to 30% of those over the age of 50 years, regardless of the
type of diet they follow, lose their ability to digest the
protein-bound form of the vitamin that is present in eggs, dairy, and
other animal products, all people over the age of 50 should use vitamin
B-12 supplements or fortified foods (92).
Studies indicate that some vegans and other vegetarians do not
regularly consume reliable sources of vitamin B-12 and that this is
reflected in less than adequate vitamin B-12 status (27,29,88,89,93-95).
It is essential that all vegetarians use a supplement, fortified food,
dairy products, or eggs to meet recommended intakes of vitamin B-12
Absorption is most efficient when small amounts of vitamin B-12
are consumed at frequent intervals. This could be achieved through use
of fortified foods. When less than 5 µg of crystalline vitamin B-12 is
consumed at one time, approximately 60% is absorbed, whereas 1% of a dose of 500 µg or higher of vitamin B-12 is absorbed (92).
Vitamin A/beta carotene
Because preformed vitamin A is found only in animal foods, vegans
get all of their vitamin A from conversion of dietary carotenoids,
particularly beta carotene. Research suggests that absorption of beta
carotene from plant foods is less efficient than previously believed (44,96).
This suggests that vegans intake of vitamin A is about half of what
previous studies have suggested, and intake by lacto-ovo-vegetarians
may be 25% lower than previously shown. Despite this, vegetarians have
been reported to have higher serum carotenoid levels than
Vitamin A requirements can be met with the inclusion of three servings
per day of deeply yellow or orange vegetables, leafy green vegetables,
or fruits that are rich in beta carotene (apricots, cantaloupe, mango,
pumpkin). Cooking increases beta carotene absorption, as does the
addition of small amounts of fat to meals (97). Chopping and pureeing vegetables may also increase bioavailability (98,99).
N-3 fatty acids
Whereas vegetarian diets are generally rich in n-6 fatty acids
(especifically linoleic acid), these diets can be low in n-3 fatty
acids, resulting in an imbalance that can inhibit production of the
physiologically active long chain n-3 fatty acids, eicosapentaenoic
acid (EPA), and docosahexaenoic acid (DHA). Diets that do not include
fish, eggs, or generous amounts of sea vegetables generally lack direct
sources of EPA and DHA. Recently, vegan sources of DHA derived from
microalgae have become available as supplements in nongelatin capsules.
Algae sources of DHA have been shown to positively affect blood levels
of DHA and of EPA through retroconversion (100).
Most studies show vegetarians, and particularly vegans, to have lower blood levels of EPA and DHA than nonvegetarians (101-104). The new Dietary Reference Intakes recommend intakes of 1.6 and 1.1 grams of -linolenic
acid per day for men and women, respectively. These are designated as
AIs rather than RDAs. These recommendations assume some intake of
long-chain n-3 fatty acids and may not be optimal for vegetarians who
consume little if any DHA and EPA (35).
The Joint World Health Organization/Food Agriculture Organization
(WHO/FAO) Expert Consultation on Diet, Nutrition and the Prevention of
Chronic Diseases (105)
recommends 5% to 8% of calories from n-6 fatty acids and 1% to 2% of
calories from n-3 fatty acids. Based on an energy intake of 2,000 kcal
per day, this would suggest a daily intake of 2.2 to 4.4 grams of n-3
fatty acids. Those who do not receive a preformed source of EPA and DHA
require increased amounts of n-3 fatty acids. The recommended ratio of
n-6 to n-3 fatty acids is in the range of 2:1 to 4:1 (106-109).
It is recommended that vegetarians include good sources of -linolenic acid in their diet (106,110). These would include foods like flaxseed and flaxseed oil (see Table).
Those with increased requirements (eg, pregnant and lactating women or
those with diseases associated with poor essential fatty acid status)
or those at risk for poor conversion (eg, people with diabetes) may
benefit from direct sources of long-chain n-3 fatty acids, such as
DHA-rich microalgae (100,106,111).
Some studies suggest that vegans who do not consume iodized salt
may be at risk for iodine deficiency; this appears to be particularly
true for those living in iodine-poor areas (29,112,113).
Bread can be a source of iodine because some dough stabilizers contain
iodine. In the United States, about 50% of the general population uses
iodized salt, whereas, in Canada, all table salt is fortified with
iodine. Sea salt and kosher salt are generally not iodized nor are
salty seasonings such as tamari. Concern has been raised about
vegetarian diets that include foods, such as soybeans, cruciferous
vegetables, and sweet potatoes, that contain natural goitrogens.
However, these foods have not been associated with thyroid
insufficiency in healthy people provided iodine intake is adequate. The
adult RDA for iodine is easily met by one-half teaspoon of iodized salt
daily (44). Some vegetarians may have very high intakes of iodine because of consumption of sea vegetables.
vegan, lacto-vegetarian, and lacto-ovo-vegetarian diets are appropriate
for all stages of the life cycle, including pregnancy and lactation.
Appropriately planned vegan, lacto-vegetarian, and lacto-ovo-vegetarian
diets satisfy nutrient needs of infants, children, and adolescents and
promote normal growth (36,114,115).
Vegetarian diets in childhood and adolescence can aid in the
establishment of lifelong healthy eating patterns and can offer some
important nutritional advantages. Vegetarian children and adolescents
have lower intakes of cholesterol, saturated fat, and total fat and
higher intakes of fruits, vegetables, and fiber than nonvegetarians (2,116-118). Vegetarian children have also been reported to be leaner and to have lower serum cholesterol levels (119-121).
When vegetarian infants receive adequate amounts of breast milk or
commercial infant formula and their diets contain good sources of
energy and nutrients such as iron, vitamin B-12, and vitamin D, growth
throughout infancy is normal. Extremely restrictive diets such as
fruitarian and raw foods diets have been associated with impaired
growth and therefore cannot be recommended for infants and children (29).
Many vegetarian women choose to breastfeed their infants (122),
and this practice should be encouraged and supported. The breast milk
of vegetarian women is similar in composition to that of nonvegetarians
and is nutritionally adequate. Commercial infant formulas should be
used if infants are not breastfed or are weaned before 1 year of age.
Soy formula is the only option for vegan infants who are not being
Soymilk, rice milk, homemade formulas, cow's milk, and goat's
milk should not be used to replace breast milk or commercial infant
formula during the first year because these foods do not contain the
proper ratio of macronutrients nor do they have appropriate
micronutrient levels for the young infant.
Guidelines for the introduction of solid foods are the same for vegetarian and nonvegetarian infants (115).
When it is time for protein-rich foods to be introduced, vegetarian
infants can have mashed or pureed tofu, legumes (pureed and strained if
necessary), soy or dairy yogurt, cooked egg yolks, and cottage cheese.
Later, foods such as cubes of tofu, cheese or soy cheese, and bite-size
pieces of soy burger can be started. Commercial, full-fat, fortified
soymilk, or cow's milk can be used as a primary beverage starting at
age 1 year or older for a child who is growing normally and is eating a
variety of foods (115).
Foods that are rich in energy and nutrients such as legume spreads,
tofu, and mashed avocado should be used when the infant is being
weaned. Dietary fat should not be restricted in children younger than 2
Breastfed infants whose mothers do not consume dairy
products, foods fortified with vitamin B-12, or B-12 supplements
regularly will need vitamin B-12 supplements (115).
Guidelines for the use of iron and vitamin D supplements in vegetarian
infants do not differ from guidelines for nonvegetarian infants. Zinc
supplements are not routinely recommended for vegetarian infants
because zinc deficiency is rarely seen (123).
Zinc intake should be individually assessed and zinc supplements or
zinc-fortified foods used during the time when complementary foods are
being introduced if the diet is low in zinc or mainly consists of foods
with low zinc bioavailability (124,125).
Lacto-ovo-vegetarian children exhibit growth similar to that of their nonvegetarian peers (114,119,126).
Little information about the growth of nonmacrobiotic vegan children is
available, although findings suggest that children tend to be slightly
smaller but within the normal ranges of the standards for weight and
height (114,122). Poor growth in children has been seen primarily in those on very restricted diets (127).
Frequent meals and snacks and the use of some refined foods
(such as fortified breakfast cereals, breads, and pasta) and foods
higher in unsaturated fat can help vegetarian children meet energy and
nutrient needs. Average protein intake of vegetarian children
(lacto-ovo, vegan, and macrobiotic) generally meets or exceeds
recommendations, although vegetarian children may consume less protein
than nonvegetarian children (116,128).
Vegan children may have protein needs that are slightly higher than
those of nonvegan children because of differences in protein
digestibility and amino acid composition of plant food proteins (36,129), but these protein needs are generally met when diets contain adequate energy and a variety of plant foods (35).
Good sources of calcium, iron, and zinc should be emphasized for
vegetarian children along with dietary practices that enhance
absorption of zinc and iron from plant foods. A reliable source of
vitamin B-12 is important for vegan children. If there is concern about
vitamin D synthesis owing to limited sunlight exposure, skin tone,
season, or sunscreen use, vitamin D supplements or fortified foods
should be used. The Table provides information about food sources of
nutrients. Food guides for vegetarian children under 4 years of age (36,130) and for older children (72,73) have been published elsewhere.
There are limited data available on the growth of vegetarian
adolescents, although studies suggest there is little difference
between vegetarians and nonvegetarians (131). In the West, vegetarian girls tend to reach menarche at a slightly later age than nonvegetarians (132,133), although not all research supports this finding (134,135).
If slightly later menarche does occur, it may offer health advantages,
including lower risk of developing breast cancer and obesity (136,137).
Vegetarian diets appear to offer some nutritional advantages for
adolescents. Vegetarian adolescents are reported to consume more fiber,
iron, folate, vitamin A, and vitamin C than nonvegetarians (2,60).
Vegetarian adolescents also consume more fruits and vegetables and
fewer sweets, fast foods, and salty snacks compared with nonvegetarian
adolescents (2,118). Key nutrients for adolescent vegetarians include calcium, vitamin D, iron, zinc, and vitamin B-12.
Vegetarian diets are somewhat more common among adolescents
with eating disorders than in the general adolescent population;
therefore, dietetics professionals should be aware of young clients who
greatly limit food choices and who exhibit symptoms of eating disorders
However, recent data suggest that adopting a vegetarian diet does not
lead to eating disorders, rather that vegetarian diets may be selected
to camouflage an existing eating disorder (27,140,141). With guidance in meal planning, vegetarian diets are appropriate and healthful choices for adolescents.
Pregnant and lactating women
Lacto-ovo-vegetarian and vegan diets can meet the nutrient and
energy needs of pregnant women. Infants of vegetarian mothers generally
have birth weights that are similar to those of infants born to
nonvegetarians and to birth weight norms (122,142,143).
Diets of pregnant and lactating vegans should contain reliable sources
of vitamin B-12 daily. If there is concern about vitamin D synthesis
because of limited sunlight exposure, skin tone, season, or sunscreen
use, pregnant and lactating women should use vitamin D supplements or
fortified foods. Iron supplements may be needed to prevent or treat
iron-deficiency anemia, which is commonly seen during pregnancy. Women
capable of becoming pregnant and women in the periconceptional period
are advised to consume 400 µg of folate daily from supplements,
fortified foods, or both in addition to consuming food folate from a
varied diet (92).
Infants of vegetarian mothers have been reported to have lower
cord and plasma DHA than do infants of nonvegetarians, although the
functional significance of this is not known (104,143). Breast milk DHA levels in vegan and lacto-ovo-vegetarian women appear to be lower than levels in nonvegetarians (144).
Because DHA seems to play a role in the development of the brain and
the eye and because a dietary supply of DHA may be important for the
fetus and newborn, pregnant and lactating vegans and vegetarians
(unless eggs are eaten regularly) should include sources of the DHA
precursor linolenic acid in their diet (ground flaxseed, flaxseed oil,
canola oil, soybean oil) or use a vegetarian DHA supplement (from
microalgae). Foods containing linoleic acid (corn, safflower, and
sunflower oil) and trans-fatty acids (stick margarine, foods
with hydrogenated fats) should be limited because these fatty acids can
inhibit DHA production from linolenic acid (145).
Studies indicate that most older vegetarians have dietary intakes that are similar to nonvegetarians (146,147).
With aging, energy needs decrease, but recommendations for several
nutrients, including calcium, vitamin D, vitamin B6, and possibly
protein, are higher. Sunlight exposure is often limited, and vitamin D
synthesis is decreased in older adults so that dietary or supplemental
sources of vitamin D are especially important.
Older adults may have difficulty with vitamin B-12 absorption
from food so vitamin B-12-fortified foods or supplements should be used
because the vitamin B-12 in fortified foods and supplements is usually
well absorbed (92).
Protein requirements for older adults are controversial. The current
DRIs do not recommend additional protein for older adults (35).
A metaanalysis of nitrogen balance studies concluded that there is not
enough evidence to recommend different protein intakes for older adults
but pointed out that the data are limited and contradictory (34). Others have concluded that protein requirements of older adults may be around 1 to 1.25 g/kg body weight (148,149).
Older adults can easily meet protein needs on a vegetarian diet if a
variety of protein-rich plant foods, including legumes and soy
products, are eaten daily.
Vegetarian diets, which are high in fiber, may be beneficial
for older adults with constipation. Older vegetarians may benefit from
nutritional counseling on foods that are easy to chew, require minimal
preparation, or are appropriate for therapeutic diets.
Vegetarian diets can also meet the needs of competitive athletes.
Nutrition recommendations for vegetarian athletes should be formulated
with consideration of the effects of both vegetarianism and exercise.
The position of the American Dietetic Association and Dietitians of
Canada on nutrition and athletic performance (39)
provides appropriate dietary guidance for athletes, although some
modification may be needed to address vegetarians' needs. Protein
recommendations for endurance athletes are 1.2 to 1.4 g/kg body weight,
whereas resistance and strength-trained athletes may need as much as
1.6 to 1.7 g/kg body weight (39). Not all groups support an increased protein need for athletes (35).
Vegetarian diets that meet energy needs and contain a variety of
plant-based protein foods, such as soy products, other legumes, grains,
nuts, and seeds, can provide adequate protein without the use of
special foods or supplements (150).
For adolescent athletes, special attention should be given to meeting
energy, protein, calcium, and iron needs. Amenorrhea may be more common
among vegetarian than nonvegetarian athletes, although not all research
supports this finding (151,152).
Female vegetarian athletes may benefit from diets that include adequate
energy, higher levels of fat, and generous amounts of calcium and iron.
Among Seventh-day Adventists (SDA), 40% of whom follow a meatless
diet, vegetarian eating patterns have been associated with lower body
mass index (BMI). In the Adventist Health Study, which compared
vegetarians and nonvegetarians within the Adventist population, BMI
increased as the frequency of meat consumption increased in both men
and women (4). In the
Oxford Vegetarian Study, BMI values were higher in nonvegetarians
compared with vegetarians in all age groups and for both men and women (112).
In a study of 4,000 men and women in England comparing the
relationship between meat consumption and obesity among meat eaters,
fish eaters, lacto-ovo-vegetarians, and vegans, mean BMI was highest in
the meat eaters and lowest in the vegans (153). BMI was lowest in those lacto-ovo-vegetarians and vegans who had adhered to their diet for 5 years or longer.
Factors that may help to explain the lower BMI among
vegetarians include differences in macronutrient content (lower
protein, fat, and animal fat intake), higher fiber consumption,
decreased alcohol intake, and greater consumption of vegetables.
An analysis of five prospective studies involving more than 76,000
subjects showed that death from ischemic heart disease was 31% lower
among vegetarian men compared with nonvegetarian men and 20% lower
among vegetarian women compared with nonvegetarian women (154).
Death rates were also lower for vegetarian men and women compared with
semivegetarians, those who ate fish only or ate meat less than once per
week. Among SDA, vegetarian men had a 37% reduction in risk of
developing ischemic heart disease compared with nonvegetarian men (4).
In the only study to include vegan subjects, risk for developing heart
disease was even lower among SDA vegan men than in the SDA
The lower rates of heart disease among vegetarians are
explained in part by their lower blood cholesterol levels. A review of
9 studies found that, in comparison to nonvegetarians,
lacto-ovo-vegetarians and vegans had mean blood cholesterol levels that
were 14% and 35% lower, respectively (156).
Although the lower average BMI of vegetarians may help to explain this,
Sacks and colleagues found that, even when vegetarian subjects were
heavier than nonvegetarian subjects, the vegetarians had markedly lower
plasma lipoprotein values (157),
and Thorogood and colleagues found that differences in plasma lipids in
vegetarians, vegans, and meat eaters persisted, even following
adjustment for BMI (158). Some, but not all, studies have shown lower high-density lipoprotein (HDL) levels in vegetarian subjects (29).
Lower HDL levels may be due to the type or amount of dietary fat or to
lower alcohol intake. This may help to explain the smaller differences
in heart disease rates between vegetarian and nonvegetarian women
because HDL may be a more important risk factor than LDL levels for
women (159). Average triglyceride levels tend to be similar in vegetarians and nonvegetarians.
A number of factors in vegetarian diets may affect cholesterol
levels. Although studies show that most vegetarians do not typically
consume low-fat diets, saturated fat intake is considerably lower among
vegetarians than nonvegetarians, and vegans have a lower ratio of
saturated to unsaturated fat in their diets (29).
Vegetarians also consume less cholesterol than nonvegetarians, although
the range of intake varies considerably across studies. Vegan diets are
free of cholesterol.
Vegetarians consume between 50% and 100% more fiber than
nonvegetarians, and vegans have higher intakes than
lacto-ovo-vegetarians (29). Soluble fiber may lower risk for cardiovascular disease by reducing blood cholesterol levels (160).
Limited research suggests that animal protein is directly associated
with higher serum cholesterol levels even when other dietary factors
are controlled (161).
Lacto-ovo-vegetarians consume less animal protein than nonvegetarians,
and vegans consume no animal protein. Research shows that consumption
of at least 25 g per day of soy protein, either in place of animal
protein or in addition to the usual diet, reduces cholesterol levels in
people with hypercholesterolemia (162). Soy protein may also raise HDL levels (162). Vegetarians are likely to consume more soy protein than the general population.
Other factors in vegetarian diets may impact cardiovascular
disease risk independent of effects on cholesterol levels. Vegetarians
have higher intakes of the vitamin antioxidants vitamins C and E, which
may reduce oxidation of LDL cholesterol. Isoflavones, which are
phytoestrogens found in soy foods, may also have antioxidant properties
(163) as well as enhancing endothelial function and arterial compliance (164).
Although there is limited information available about intake of
specific phytochemicals among population groups, vegetarians appear to
consume more phytochemicals than nonvegetarians because a greater
percentage of their energy comes from plant foods. Some phytochemicals
may affect plaque formation through effects on signal transduction and
cell proliferation (165) and may exert antiinflammatory effects (166).
Research from Taiwan found that vegetarians had significantly better
vasodilation responses, which correlated directly with years on a
vegetarian diet, suggesting a direct beneficial effect of vegetarian
diet on vascular endothelial function (167).
Not all aspects of vegetarian diets are associated with reduced risk for heart disease. Some (89,103,168-171) but not all (62,172)
studies have found higher serum homocysteine levels in vegetarians
compared to nonvegetarians. Homocysteine is believed to be an
independent risk factor for heart disease. Inadequate intake of vitamin
B-12 may be the explanation. Vitamin B-12 injections lowered
homocysteine levels in vegetarians, many of whom had low B-12 levels
and high serum homocysteine (173).
In addition, low intakes of n-3 fatty acids and a high ratio of n-6 to
n-3 fatty acids in the diet may raise risk of heart disease among some
There are only limited data on the role of vegetarian diets as
intervention for heart disease. Vegetarian diets used in these studies
have usually been very low in fat. Because these diets have been used
along with other lifestyle changes and they have produced weight loss,
it has not been possible to ascertain any direct effect of adoption of
vegetarian diet on risk factors for heart disease or mortality.
Vegetarian diets can be planned to conform to standard recommendations
for the treatment of hypercholesterolemia.
Many studies show that vegetarians have both lower systolic and
diastolic pressures with differences between vegetarians and
nonvegetarians generally falling between 5 and 10 mm Hg (29).
In the Hypertension Detection and Follow-Up Program, blood pressure
reduction of just 4 mm Hg caused marked reduction in mortality from all
In addition to having lower blood pressures in general, vegetarians have markedly lower rates of hypertension than meat eaters (175,176).
In one study, 42% of nonvegetarians had hypertension (defined as 140/90
mm Hg) compared with only 13% of vegetarians. Even semivegetarians are
50% more likely to have hypertension than vegetarians (4).
Even when body weights were similar between subjects, vegetarians had
lower blood pressures. Placing nonvegetarian subjects on a vegetarian
diet led to reduced blood pressure in normotensive (177) and hypertensive subjects (178).
A number of studies have controlled for various factors that
might help to explain the lower blood pressures of vegetarians and the
hypotensive effects of changing to a vegetarian diet. The lower blood
pressures do not appear to be due to lower BMI (175), exercise habits (179), absence of meat (180), milk protein (181), fat content of diet (182), fiber (183) or differences in potassium, magnesium, or calcium intakes (184).
Because sodium intake of vegetarians is comparable or only modestly
lower than that of nonvegetarians, sodium does not explain the
differences either. Suggested explanations include a difference in
blood glucose-insulin response because of a lower glycemic index of
vegetarian diets (185) or a collective effect of beneficial compounds from plant foods (186).
Vegetarian diets can meet guidelines for the treatment of diabetes (187),
and some research suggests that diets that are more plant-based reduce
risk for type 2 diabetes. Rates of self-reported diabetes among
Seventh-day Adventists (SDA) were less than half those of the general
population, and, among SDA, vegetarians had lower rates of diabetes
than nonvegetarians (188).
In the Adventist Health Study, age-adjusted risk for developing
diabetes for vegetarian, semivegetarian, and nonvegetarian men was
1.00, 1.35, and 1.97, respectively, and, for women, it was 1.00, 1.08,
and 1.93 (4). Among the
possible explanations for a protective effect of vegetarian diet are
the lower BMI of vegetarians and higher fiber intake, both of which
improve insulin sensitivity. However, among men in the Adventist Health
Study, risk for diabetes was still 80% higher in nonvegetarian men
after adjustment for weight. In men, meat consumption was directly
associated with increased risk of diabetes. Among women, risk increased
only when meat consumption exceeded five servings per week (188).
Vegetarians have an overall lower cancer rate compared with the
general population, but it is not clear to what extent this is due to
diet. When nondietary cancer risk factors are controlled for,
differences in overall cancer rates between vegetarians and
nonvegetarians are greatly reduced, although marked differences remain
in rates of certain cancers. An analysis from the Adventist Health
Study that controlled for age, sex, and smoking found no differences
between vegetarians and nonvegetarians for lung, breast, uterine, or
stomach cancer but did find that nonvegetarians had a 54% increased
risk for prostate cancer and an 88% increased risk for colorectal
cancer (4). Other research has shown lower rates of colon cell proliferation in vegetarians compared with nonvegetarians (189)
and lower levels of serum insulin-like growth factor-I, thought to be
involved in the etiology of several cancers in vegans compared with
both nonvegetarians and lacto-ovo-vegetarians (190). Both red and white meat have been independently linked to increased risk for colon cancer (4).
Observational studies have found an association between high intake of
dairy foods and calcium with increased risk for prostate cancer (191-193), although not all studies support this finding (194). A pooled analysis of 8 observational studies found no link between meat or dairy consumption and breast cancer (195).
Research suggests that a number of factors in vegetarian diets
may impact cancer risk. Vegetarian diets come closer to matching the
dietary guidelines issued by the National Cancer Institute than do
nonvegetarian diets, particularly in regard to fat and fiber intakes (196).
Although data on fruit and vegetable intake of vegetarians are limited,
a recent study found that intake was considerably higher among vegans
compared with nonvegetarians (62).
High lifetime exposure to estrogen has been linked to increased breast
cancer risk. Some research shows that vegetarians have lower serum and
urinary estrogen levels (197).
There is also some evidence that vegetarian girls begin menstruation at
a later age, which may reduce cancer risk because of lower lifetime
estrogen exposure (132,133). High fiber intake is believed to protect against colon cancer, although not all research supports this (198,199).
The environment of the colon of vegetarians is strikingly different
from that of nonvegetarians. Vegetarians have a lower concentration of
potentially carcinogenic bile acids (200) and fewer intestinal bacteria that convert the primary bile acids into carcinogenic secondary bile acids (201). More frequent elimination and the levels of certain enzymes in the colon enhance elimination of potential colon carcinogens (200,202). Most research shows that vegetarians have lower levels of fecal mutagens (203).
Vegetarians do not consume heme iron, which has been shown to
lead to the formation of highly cytotoxic factors in the colon
increasing colon cancer risk (204).
Finally, vegetarians most likely have higher intakes of phytochemicals,
many of which have anticancer activity. Isoflavones in soy foods have
been shown to have anticancer effects, particularly in regard to breast
and prostate cancer, although this is not supported by all research (205,206).
Osteoporosis is a complex disease affected by a variety of
lifestyle, dietary, and genetic factors. Although some data indicate
that osteoporosis is less common in developing countries with a mostly
plant-based diet, these studies have relied on hip fracture data, which
has been found to be unreliable for comparing bone health across
cultures. There is little evidence to suggest that bone mineral density
differs between western nonvegetarians and lacto-ovo-vegetarians.
A number of studies have shown that high protein intake, from
animal foods in particular, causes increased excretion of calcium and
raises calcium needs (207-209).
The effect is believed to be due to the increased acid load from
metabolism of sulfur-containing amino acids (SAA). However, grains are
also high in these amino acids, and some research shows that SAA intake
was similar between nonvegetarians and vegetarians (210).
Despite this, there is some evidence that postmenopausal women with
diets high in animal protein and low in plant protein had a high rate
of bone loss and a greatly increased risk of hip fracture (211).
Although excessive protein intake may compromise bone health, there is
evidence that low protein intakes could raise risk for poorer bone
health (212). Although
there are very little reliable data on bone health of vegans, some
studies suggest that bone density is lower among vegans compared with
Vegan women, like other women, may have low calcium intakes despite the
availability of nondairy sources of well-absorbed calcium. Some vegan
women may also have protein intakes that are marginal, and vitamin D
status has shown to be compromised in some vegans (216-218).
The lower serum estrogen levels of vegetarians may be a risk factor for
osteoporosis. In contrast, short-term clinical studies suggest that soy
protein rich in isoflavones decreases spinal bone loss in
postmenopausal women (219).
Higher intake of potassium and vitamin K among vegetarians may also
help to protect bone health. However, the data suggest that a
vegetarian diet does not necessarily protect against osteoporosis
despite lower animal protein content.
High intake of dietary protein may worsen existing kidney disease
or increase risk for those who are susceptible to this disease because
protein intake is associated with a higher glomerular filtration rate
(GFR) (220). The GFR of healthy vegetarians is lower than that of nonvegetarians and even lower in vegans (221).
The type of protein consumed may also have an effect, with plant foods
having a more beneficial effect on GFR than animal protein (222, 223). GFR was 16% higher in healthy subjects after eating a meal containing animal protein compared with a meal with soy protein (222).
Because the pathology of renal disease is similar to that of
atherosclerosis, the lower serum cholesterol levels and reduced
cholesterol oxidation resulting from a vegetarian diet may be
beneficial for those with kidney disease.
Although rates of dementia differ markedly throughout the world,
differences in diagnostic criteria make cross-cultural comparisons
difficult. In the United States, among SDA, those who ate meat were
more than twice as likely to develop dementia (224).
Those who had eaten meat for many years were more than three times as
likely to develop signs of dementia. Diets high in antioxidants have
been found to protect cognitive function (225-227).
The lower blood pressure of vegetarians may also be protective. There
is also some evidence that lower blood cholesterol protects against
dementia (228). Higher
homocysteine levels are linked to increased risk of dementia, and this
may present one risk factor for vegetarians who do not get adequate
vitamin B-12 (229-232). Although one observational study found an increased rate of dementia among Japanese American men who ate tofu regularly (233), the study had a number of methodological limitations, and other research has not supported these findings (234).
Other health effects of vegetarian diets
Gear and colleagues found that both male and female vegetarians
aged 45 to 59 years were 50% as likely to have diverticulitis compared
with nonvegetarians (235).
Although fiber is believed to be the most important reason for this
difference, other factors may have an effect as well. High-fat diets,
independent of fiber intake, have been associated with increased risk
of diverticulitis (236). Meat intake may also increase risk (236).
Older research suggests that meat consumption may promote growth of
bacteria that produce a toxic metabolite that weakens the wall of the
In a study of 800 women aged 40 to 69 years, nonvegetarians were
more than twice as likely as vegetarians to suffer from gallstones (238). The relationship held even after controlling for the three known risk factors for gallstones: obesity, gender, and aging.
Rheumatoid arthritis (RA), believed to be an autoimmune disease,
involves inflammation of the joints. Several studies from one group of
researchers in Finland suggest that fasting, followed by vegan diet,
may be useful in treatment of RA (239,240).
Although data are very limited and more follow-up is needed
before conclusions can be drawn, some studies suggest that a mostly raw
foods vegan diet reduces symptoms of fibromyalgia (241) and that a vegetarian diet may reduce symptoms of topical dermatitis (242).
Special Supplemental Nutrition Program for Women, Infants, and Children
In the United States, the Special Supplemental Nutrition Program
for Women, Infants, and Children (WIC) is a federal grant program that
serves pregnant, postpartum, and breastfeeding women and infants and
children up to 5 years of age who are documented as being at
nutritional risk and with family income below state standards. This
program provides checks or coupons to purchase some foods suitable for
vegetarians, including infant formula, iron-fortified infant cereal,
vitamin C-rich fruit or vegetable juice, carrots, cow's milk, cheese,
eggs, iron-fortified ready-to-eat cereal, dried beans or peas, and
peanut butter. Individual state agencies are allowed to submit a plan
to USDA's Food and Nutrition Service for substitution of foods to allow
for different cultural eating patterns, provided the proposed
substitute food is nutritionally equivalent or superior to the food it
replaces, is widely available, and does not cost more than the food it
is to replace (243). This provision could possibly allow more foods suitable for vegans to be purchased.
Canada Prenatal Nutrition Program (CPNP), federally funded by
Health Canada, and perinatal community programs provide vouchers,
coupons, or groceries to those who meet the income and nutritional risk
criteria for the program. Vouchers can be used for some foods
acceptable to vegetarians, including milk, juice, cheese, eggs,
fortified soymilk, and other foods (244).
Child Nutrition Programs
In the United States, the National School Lunch Program (NSLP)
allows nonmeat protein products, including certain soy products,
cheese, eggs, cooked dried beans or peas, yogurt, peanut butter, other
nut or seed butters, peanuts, tree nuts, and seeds to be used (245,246). USDA information for school foodservice personnel includes several vegetarian and vegan quantity recipes (247).
Few public schools regularly feature vegetarian menu items. School
lunches are not adequate for vegans even when some vegan options are
available because soymilk can only be served as a part of school lunch
in cases of documented lactose intolerance.
In Canada, school lunch, breakfast, and snack programs; food
selection standards; and provision for vegetarian meals vary from one
region to another. Nationally, the Canadian Living Foundation's
Breakfast for Learning program is developing Best Practice Program
Standards for breakfast, snack, and lunch programs. Vegetarian meals
based on Canada's Food Guide to Healthy Eating fit within this
Feeding Programs for the Elderly
The federal Elderly Nutrition Program (ENP) distributes funds to
states, territories, and tribal organizations for a national network of
programs that provide congregate and home-delivered meals (often known
as Meals on Wheels) for older Americans. Meals served under this
program must provide at least one-third of the RDAs (249).
Meals are often provided by local Meals on Wheels agencies. A 4-week
set of vegetarian menus has been developed for use by the National
Meals on Wheels Foundation (250,251).
Court rulings in the United States and Canada have granted prison
inmates the right to have vegetarian meals for religious and medical
reasons (and in Canada, by choice, as well) (252,253).
Federal institutions and those for many states and provinces provide
vegetarian options for meals. The Canadian federal court has ruled that
prison inmates who are opposed to eating meat have a constitutional
right to be served vegetarian meals. The Freedom of Conscience
provisions in the Charter of Rights allow prisoners to demand
vegetarian fare for moral reasons, just as other inmates may request
special meals on religious or medical grounds (252).
The US Army's Combat Feeding Program, which oversees all food regulations, provides a choice of vegetarian menus (254). Canadian Forces Food Services offers one or more vegetarian options at every meal (255). An estimated 10% to 15% of Canadian Forces members choose vegetarian meals for combat rations (individual meal packs) (256).
Other institutions and quantity food service organizations
Other institutions, including colleges, universities, hospitals,
restaurants, and publicly funded museums and parks offer varying
amounts and types of vegetarian selections. Resources are available for
vegetarian quantity food preparation (Figure 1).
Fig. 1. Useful Web sites.
General Vegetarian Nutrition:
Food and Nutrition Information Center, USDA
Loma Linda University Vegetarian Nutrition & Health Letter
Seventh-day Adventist Dietetic Association
The Vegan Society (vitamin B-12)
Vegetarian Nutrition Dietetic Practice Group
Vegetarian Resource Group
The Vegetarian Society of the United Kingdom
Happy Cow's Global Guide to Vegetarian Restaurants
Vegetarian Resource Group
Quantity Food Preparation:
Vegetarian Resource Group
clients may seek nutrition counseling services for a specific clinical
condition or for assistance in planning healthful vegetarian diets.
They may sometimes be referred because of problems related to poor diet
choices. Dietetics professionals have an important role in supporting
clients who express an interest in adopting vegetarian diets or who
already eat a vegetarian diet. It is important for dietetics
professionals to support any client who chooses this style of eating
and to be able to give current accurate information about vegetarian
nutrition. Information should be individualized depending on type of
vegetarian diet, age of the client, food preparation skills, and
activity level. It is important to listen to the client's own
description of his or her diet to ascertain which foods can play a role
in meal planning. Figure 1 provides a listing of Web resources on
vegetarianism. Figure 2 includes meal planning tips.
Fig. 2. Meal planning.|
of menu planning approaches can provide adequate nutrition for
vegetarians. The Vegetarian Food Guide Pyramid and Vegetarian Food
Guide Rainbow (72,73) suggest one approach. In addition, the following guidelines can help vegetarians plan healthful diets:
Choose a variety of foods including whole grains, vegetables, fruits,
legumes, nuts, seeds, and if desired, dairy products, and eggs.
Choose whole, unrefined foods often and minimize the intake of highly sweetened, fatty and heavily refined foods.
Choose a variety of fruits and vegetables.
If animal foods such as dairy products and eggs are used, choose
lower-fat dairy products and use both eggs and dairy products in
Use a regular source of vitamin B-12 and, if sunlight exposure is limited, of vitamin D.
Click on Image to view full size
Qualified dietetics professionals can help vegetarian clients in the following ways:
information about meeting requirements for vitamin B-12, calcium,
vitamin D, zinc, iron, and n-3 fatty acids because poorly planned
vegetarian diets may sometimes fall short of these nutrients;
- give specific guidelines for planning balanced lacto-ovo-vegetarian or vegan meals for all stages of the life cycle;
guidelines for planning balanced lacto-ovo-vegetarian or vegan meals
for clients with special dietary needs because of allergies or chronic
disease or other restrictions;
- be familiar with vegetarian options at local restaurants;
- provide ideas for planning optimal vegetarian meals while traveling;
clients about the preparation and use of foods that frequently are part
of vegetarian diets; the growing selection of products aimed at
vegetarians may make it impossible to be knowledgeable about all such
products. However, practitioners working with vegetarian clients should
have a basic knowledge of preparation, use, and nutrient content of a
variety of grains, beans, soy products, meat analogs and fortified
- be familiar with local sources for purchase of vegetarian foods. In some communities, mail order sources may be necessary.
with family members, particularly the parents of vegetarian children,
to help provide the best possible environment for meeting nutrient
needs on a vegetarian diet; and,
a practitioner is unfamiliar with vegetarian nutrition, he/she should
assist the individual in finding someone who is qualified to advise the
client or should direct the client to reliable resources.
planned vegetarian diets have been shown to be healthful, nutritionally
adequate, and beneficial in the prevention and treatment of certain
diseases. Vegetarian diets are appropriate for all stages of the life
cycle. There are many reasons for the rising interest in vegetarianism.
The number of vegetarians in the United States and Canada is expected
to increase over the next decade. Dietetics professionals can assist
vegetarian clients by providing current, accurate information about
vegetarian nutrition, foods, and resources.
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Position adopted by the House of Delegates on October 18, 1987, and
reaffirmed on September 12, 1992, September 6, 1996 and June 22, 2000.
This position was developed collaboratively between the American
Dietetic Association and Dietitians of Canada. This position will be in
effect until December 31, 2007. ADA authorizes republication of the
position statement/support paper, in its entirety, provided full and
proper credit is given. Requests to use portions of the position must
be directed to ADA Headquarters at 800/877-1600, ext 4835, or email@example.com Recognition is given to the following for their contributions:
Ann Reed Mangels, PhD, RD, FADA (The Vegetarian Resource Group, Baltimore, MD);
Virginia Messina, MPH, RD (Nutrition Matters, Inc., Port Townsend, WA);
Vesanto Melina, MS, RD (NUTRISPEAK.COM, Langley, BC, Canada).
American Dietetic Association Reviewers:
Judith G. Dausch, PhD, RD (American Dietetic Association Government Relations, Washington, DC);
Sharon Denny, MS, RD (American Dietetic Association Knowledge Center, Chicago, IL);
Elaine K. Fleming, MPH, RD (Loma Linda University, Loma Linda, CA);
and Culinary Professionals DPG (Robin Kline, MS, RD, CCP, Savvy Food
Communications, Des Moines, IA; Sylvia E. Klinger, MS, RD, Hispanic
Food Communications, La Grange, IL);
D. Enette Larson-Meyer, PhD, RD (Pennington Biomedical Research Center, Baton Rouge, LA);
in Complementary Care DPG (Dennis Gordon, MEd, RD, Saint Joseph Mercy
Health System, Ann Arbor, MI; Rita Batheja, MS, RD, Private Practice,
Long Island, NY);
Nutrition DPG (Maria Hanna, MS, RD, Children's Hospital of
Philadelphia, Philadelphia, PA; Cristine M. Trahms, MS, RD, FADA,
University of Washington, Seattle, WA; Tamara Schryver, MS, RD,
University of Minnesota, St. Paul, MN);
Cardiovascular, and Wellness Nutritionist DPG (Gita B. Patel, MS, RD,
Alice Peck Day Memorial Hospital, Lebanon, NH; Pamela J. Edwards, MS,
RD, University of Nebraska Lincoln, Lincoln, NE);
Nutrition DPG (Winston J. Craig, PhD, RD, Andrews University, Berrien
Springs, MI; Catherine Conway, MS, RD, Private Practice, New York, NY);
Women and Reproductive Nutrition DPG (Judith B. Roepke, PhD, RD, Ball State University, Muncie, IN).
Dietitians of Canada Reviewers:
Karen Birkenhead, RD, (Group Health Centre, Sault Ste Marie, ON);
Samara Felesky Hunt (Consulting Dietitian, Calgary AB);
Susie Langley MS, RD (Nutrition Consultant in Private Practice, Toronto, ON);
Pam Lynch, MHE, RD (Nutrition Counselling Services, Halifax, NS);
Shefali Raja (Vancouver Coastal Health Authority, Vancouver BC);
Marilyn Rabin PDt (Douglas Hospital, Verdun, PQ);
Laura Toews, RD (St. Boniface General Hospital, Winnipeg, MB).
Members of the Association Positions Committee Workgroup:
Barbara Emison Gaffield, MS, RD (chair), Barbara Baron, MS, RD; Suzanne Havala Hobbs, DrPH, RD, FADA (content advisor).
Copyright İ 2003 by the American Dietetic Association.