Reed Mangels, PhD, RD, FADA

QUESTION: “Every year, experts seem to arise out of nowhere to suggest that vegetarianism is not a viable dietary choice. I remember hearing that vegetarians have increased risk for cancer, and that vegetarians risk not getting enough protein, and each time, a follow-up study allayed my fears. Can you provide an analysis that lays these and future criticisms to rest?” EB, MD

ANSWER: Several large studies of vegetarians can give us the information we need to address this question. Many of these have followed a group of vegetarians for a long time, long enough to see if health problems would be more likely to develop in vegetarians. The value of looking at a large group of vegetarians, rather than a few people, is that it gives us a better perspective on which conditions are and are not related to the vegetarian diet. For example, suppose you were to look at a group of ten vegetarians who were in a support group because they were attempting to make lifestyle changes (including a change to a vegetarian diet) after having a heart attack. You might find that this group was overweight, had high cholesterol, and high blood pressure. You may come to the conclusion that a vegetarian diet caused all these problems if you looked only at this small group. If, on the other hand, you looked at a group of 1,000 vegetarians, it is more likely that they would be a varied group and more representative of vegetarians as a whole. Some might have had heart attacks, some would have high blood pressure, and some would be very healthy.

The largest study conducted on vegetarians combined data from four different countries to compare a total of 27,808 vegetarians to approximately 48,000 non-vegetarians. This study found that vegetarians had a 24% lower mortality from heart disease than did non-vegetarians. While there was no significant difference in mortality from cerebrovascular disease or cancer of the stomach, colon, lung, breast, or prostate in vegetarians when compared to non-vegetarians, this study certainly suggests that vegetarianism is a viable dietary choice, offering health benefits.

A study of 30,000 California Seventh-day Adventists, 30% of whom are vegetarian, followed subjects for 25 years to assess their health status. Vegetarians were found to have much lower risk of obesity, hypertension, diabetes, colon and prostate cancer, and arthritis. Vegetarian men were less likely to develop fatal heart disease. Other large studies have found that vegans and vegetarians have lower blood cholesterol levels and LDL-cholesterol levels than non-vegetarians.

Vegetarians have been shown to have longer life-expectancies (see pages 24-25), use fewer medications and health services, and have fewer surgeries than do non-vegetarians.

“But what about protein, or molybdenum, or pantothenic acid, or biotin?” you may be saying. “Didn't I hear somewhere that vegetarian diets are deficient in some nutrient?” A vegetarian diet can certainly be deficient in one or more nutrients, especially if it is a very limited diet that has little variety in foods, does not contain enough calories, or relies heavily on “junk foods” (like snack chips, sodas, sweets, alcoholic beverages). On the other hand, a vegetarian diet featuring a variety of foods (including whole grains, dried beans, fruits, vegetables, and reliable sources of vitamin B12 and vitamin D), containing enough calories, and with few junk foods, will generally provide the nutrients you need.

When you hear of a study purporting to show that vegetarian diets are deficient in one or more essential nutrients, it is important to ask some questions.

  • Was the study of just one vegetarian or of a small group of vegetarians who might have been eating a very limited diet?
  • Was the study of vegetarians in a country where food safety or adequacy is a major issue? If so, the results may not apply to vegetarians living in countries with easy access to a varied, hygienic diet.
  • Was the study done recently? Some studies from the 1960s and 1970s are still being cited as evidence for concerns about vegetarian diets. Today's vegetarian diets typically feature larger variety and more fortified foods than did vegetarian diets 30 or 40 years ago.
  • Could factors other than diet have affected the results?
  • Who paid for the study? Might that affect the findings?
  • Was this a preliminary study? Have other studies reached the same conclusions?

The bulk of the evidence is that vegetarians live long and healthy lives. If you hear of an isolated study showing that a small number of vegetarians develop one problem or another (perhaps unrelated to their diet), try not to be alarmed. Evidence strongly supports the healthfulness of a vegetarian diet.