It used to be that scientific research on vegetarian diets questioned their nutritional adequacy, particularly with regard to their protein content. But as most of these concerns have faded in recent years, researchers have begun studying vegetarian diets with respect to their role in both the prevention and treatment of disease.

As a result, there has been a growing appreciation for the benefits of vegetarian diets or those that include generous amounts of plant foods and limited amounts of animal foods. The American Institute for Cancer Research, the American Cancer Society, and the National Institutes of Health are some of the many health organizations now recommending these types of diets. Both the American Dietetic Association and Dietitians of Canada support appropriately planned vegetarian diets as "healthful, nutritionally adequate, and providing health benefits in the prevention and treatment of certain diseases." Vegetarianism has come a long way !

Technically, a vegetarian is defined as a person who does not eat meat, fish or fowl or products that contain them. However, in reality, the eating patterns of vegetarians can vary considerably, from strict vegetarians (vegans), to those who include dairy and/or fish in their diet. Some self-described vegetarians may even include occasional fish, chicken, and meat in their diet.

Health benefits

Much of what we know about the health benefits of vegetarian diets comes from studies of Seventh-day Adventists. A high percentage of vegetarians is found among the adherents of this religious group. Many Seventh-day Adventists are strict vegans, others merely avoid meat. However, Seventh-day Adventists, as well as other vegetarians, often have healthier lifestyles in general, so it's difficult to link the health benefits of their lifestyle to any single dietary factor, such as the absence of animal foods.

Obesity. Plant-based diets have long been associated with decreased obesity, which is a risk factor for may chronic diseases, including heart disease, high blood pressure, diabetes, and some cancers. Some factors that may help explain lower body weight in vegetarians include lower fat intake, higher fiber consumption, and greater consumption of vegetables.

Cardiovascular disease. Numerous studies have shown a decreased incidence of heart disease among vegetarians compared with nonvegetarians. This may be explained in part by lower blood cholesterol levels in vegetarians. Compared to nonvegetarians, lacto-ovo-vegetarians and vegans have blood cholesterol levels 14 percent and 35 percent lower, respectively. Although most vegetarians don't eat low-fat diets, their saturated fat intake is considerably lower than that of nonvegetarians. They also consume between 50 to 100 percent more fiber, which helps reduce blood cholesterol levels. In addition, a vegetarian diet has the benefit of the many phytochemicals found in plant foods that have antioxidant properties, and antioxidants make blood cholesterol less likely to stick to artery walls.

Hypertension. In addition to having lower blood pressure in general, vegetarians also have lower rates of hypertension (high blood pressure) than nonvegetarians. Researchers have looked at possible explanations for this difference, including lower body weight, decreased dietary fat, absence of meat or milk protein, or differences in potassium, magnesium, or calcium intakes, but so far they have not been able to draw any conclusions.

Cancer. Vegetarians in general have a lower cancer rate compared to the general population. This difference is most significant for prostate cancer and colorectal cancer. A number of factors in vegetarian diets may affect cancer risk, such as lower fat consumption, more fiber, more fruits and vegetables, lower levels of heme iron (from animal sources) and higher intake of phytochemicals like isoflavones, hormonelike plant compounds found in soy and other plant foods.

Diabetes. There is some evidence that vegetarians have lower rates of diabetes. this protective effect may be the result of lower body weight among vegetarians, as well as a higher fiber intake, which can both improve blood sugar control.

Children's needs

Children have high nutrient requirements, but they have small stomachs, so a strict vegetarian diet, containing mainly fruits and vegetables, whole grains, and a lot of bulky fiber, may be too low in calories and nutrients to meet a child's needs. But with some careful planning, a balanced vegan diet with good sources of protein and some concentrated sources of energy can adequately support growth and nutrition.

The daily diet should include: three meals plus plenty of appealing snacks like trail mix, muffins, and whole-grain cookies; sources of fat, such as nuts, seeds, avocados, and nut-butters; and plenty of protein-rich foods like tofu, nut-butters, soy cheese, and yogurt.

Vegetarians may need more iron and zinc

Phytates, compounds found mostly in cereal grains, legumes, and nuts, bind with iron and prevent the body from using it. Vegetarians should increase their intake of plant foods that are rich in iron, or should discuss the use of an iron supplement with their doctor. The Recommended Dietary Allowance (RDA) of iron for vegetarians who eat no animal products is 1.8 times greater than the RDA for nonvegetarians. For example, a 30-year-old vegetarian woman will need 32 mg instead of 18 mg daily. Vitamin C can help reduce the effects of phytates, and cooking or baking vegetables also releases some of the iron that is bound to the phytates.