Vegetarian Nutrition

The human intestinal tract will tolerate a fairly broad diet. Human beings are probably designed to be omnivores with a significant leaning toward the vegetarian end of the spectrum. It is well established that a diet high in animal-source fats and proteins contributes to increased risk of heart disease, obesity, hypertension, and colon cancer.

Vegetarians face some nutritional challenges, however. Especially, vegans, those vegetarians who eat no animal products at all (including eggs and dairy products). Some essential nutrients may be difficult to obtain in a vegetarian diet without some effort. Complete proteins, iron, B12, and vitamin D are the nutrients needing special consideration in a vegetarian diet.

It was once believed that vegetarians needed to combine vegetable sources of protein at each meal in order to get all the essential amino acids. This idea is less accepted today. However, it is important for vegetarians to consume all the essential amino acids throughout a week’s time by eating from a variety of vegetable protein sources. The classic vegetarian meal of rice and beans, as a method of combining “complementary proteins”, is still a great way to obtain all the essential amino acids.

Vitamin B12 (cyanocobalamin) is difficult to get from vegetarian sources. Since it is stored in the liver for years at time, a deficiency of B12 may take years (even decades) to appear. Pernicious anemia, the deficiency disease of vitamin B12, has been documented in vegans. Vegans may obtain B12 from fortified soy milk and cereals. Vitamin B12 is particularly poorly absorbed when taken in tablet form, and thus, B12 supplements are often given by injection to treat pernicious anemia.

Vitamin D is essential for healthy bone, teeth and the absorption of calcium. The human body requires only small amounts of vitamin D. Vitamin D is produced in the skin upon exposure to sunlight. Since exposure to sunlight is dependent upon lifestyle, climate and opportunity, Vitamin D has been added to milk to assure a readily available source (especially for children). But it can be found in grains, nuts, legumes and some leafy vegetables. The adult form of vitamin D deficiency, osteomalacia, has been seen in vegans and vegetarians with a low- or non-fat diet.

Iron is readily found in vegetables, especially beans. However, vegetable sources of iron are usually in the ferric state of the iron ion, as opposed to the more readily digestible ferrous state. Adequate amounts of vitamin C can enhance the absorption of the ferric form of iron.