To most people in the industrialized world, the word vegetarian conjures up images of carrots and lettuce leaves, but nothing could be further from the truth. Vegetarian diets can be very satisfying indeed, as underscored by most of mankind that has subsisted for much of human history on vegetarian or near-vegetarian diets. Even in this modern age, the vast majority of the people who inhabit this planet survive on a largely vegetarian diet.ⁱ A prime example are the Hunza people of the Himalayas who are known for their disease-free society and longetivity. The Tarahumara Indians of Mexico are also renowned for their stamina and vibrant health, yet both these tribes subsist on largely vegetarian whole-food diets.ⁱⁱ Vegetarian lifestyles are becoming more and more popular, and many people are adopting the vegetarian diet for reasons of health, religious beliefs, philosophical considerations, or environmental convictions. However, not all the vegetarian practices dictated by some of these convictions are equally beneficial, and some of them, particularly those dictated by religious or metaphysical beliefs, can place severe restrictions on the utilization of certain foods. Moreover, some groups, in addition to following restrictive diets, shun the expertise of nutritional science and the medical profession, and run the risk of suffering malnutrition and associated diseases.

Vegetarians can be divided into three categories, depending on the range of foods which are included in the diet:

1. Vegan vegetarians avoid all animal products.

2. Lacto vegetarians include dairy products in their diet.

3. Lacto-ovo-vegetarians include dairy products and eggs in their diet.

Dairy products should, if possible, not be included in the human diet, and the other animal products also have their health risks, particularly in view of modern husbandry practices and the rising incidence of food-borne diseases. However, a diet that excludes all animal products might seem restrictive, and indeed can be, if certain criteria are not met. The more restrictive the diet, the greater the chance of developing deficiencies and nutrient-deficiency related diseases. Risks will increase if single-plant food regimes are adopted such as diets consisting only of fruit or only of legumes or only of cereals. The higher diet levels of the Zen macrobiotic diet are, for example, made up entirely of cereals, and cases of scurvy, anemia, hypoproteinemia, hypocalcemia, and even death from malnutrition have resulted from this lifestyle.^iii,iv

Vegan vegetarian diets must be well planned, and special attention must be given to nutrients which occur in low levels or are absent from plant foods. Moreover, pregnant or lactating women and infants and growing children also need specific dietary consideration. However, if due consideration to these points is given, a total plant-based diet can supply all our dietary needs. A variety of plant foods, incorporating grains, nuts, seeds, legumes, fruits, and vegetables, will supply ample nutrients for healthful living. Nutritionists often express skepticism as to the adequacy of a vegetarian diet, and their main concerns revolve around adequacy of proteins, calcium, iron, riboflavin, and vitamin B12. 

If combinations of cereals and legumes are used, protein deficiency is extremely unlikely, and numerous studies have proven not only the adequacy, but also the superiority of plant proteins over those of animal origin.^ii,v Indeed, the reverse is true in that it is difficult not to exceed recommended protein allowances on a varied vegetarian diet. It is only when calorie needs are not met that the body will preferentially utilize proteins as an energy source, and this may result in deficiencies. Such conditions are mostly found in populations where malnutrition is a common phenomenon. Regarding the other nutrients listed, all these nutrient requirements can be met by plant foods, except for vitamin B12, but this can be supplied through fortified soybean milk, nutritional yeast grown on a B12 medium, or through supplementation.^vi,vii Even without supplementation, reports of vegans suffering from vitamin B12 deficiency are extremely rare.

This article is adapted from the book Diet and Health by Dr. Walter Veith. Updated January 2009.

i "Position paper on the vegetarian approach to eating," Journal of the American Dietetic Association 77 (1980):61-69.

ii B. Balke and C. Snow, "Anthropological and physiological observations on Tarahumara endurance runners," American Journal of Physical Anthropology 23 (1965): 293-301.

iii U.D. Register and L.M. Sonnenberg, "The vegetarian diet," Journal of the American Dietetic Association 62 (1973): 253-261.

iv Council on foods and Nutrition, "Zen Macrobiotic diets," Journal of the American Medical Association 218 (1971):397.

v D.A. Snowdon, "Animal product consumption and mortality of all causes combined, coronary heart disease, stroke, diabetes and cancer in Seventh-day Adventists," American Journal of Clinical Nutrition 48 (1988): 739-48.

vi P.B. Mutch, "Food guides for the vegetarian," American Journal of Clinical Nutrition 48 (1988):913-919.

vii D.C. Nieman, "Vegetarian dietary practices and endurance performance," American Journal of Clinical Nutrition 48 (1988):754-61.