11.6: Vegetarian Diets

As noted earlier, many of the vegetarians throughout the world aren’t vegetarians by choice. They’d eat animal food if it were available and/ or affordable. They suffer from the many ills of poverty, and their strictly vegetarian diet typically is a poor one.

In this country, most vegetarians are among the more affluent, and have a readily available variety of food rich in protein (e.g., beans) and calories (e.g., nuts, salad oils). Moreover, many are lacto-ovo-vegetarians (include milk and egg) rather than vegans (plant food only). Milk and egg are not only rich sources of high-quality protein, but have other important nutrients, e.g., milk is a good source of the B-vitamin riboflavin, which is often low in strictly vegetarian diets.

The RDA for protein assumes a mixed diet of plant and animal foods. So for the vegan, the recommended intake is about 25% higher. For adults, combining proteins can be rather casual, e.g., tortillas at lunch and beans at dinner. But young children should combine plant proteins at the same meal. They have a greater need for high-­quality protein.

As long as vegan diets include a variety of nutritious foods and are adequate in calories, protein generally isn’t a nutritional concern. But some other nutrients tend to be low. As discussed in Chapter 7, vitamin B12 can be lacking in vegan diets, since it’s found naturally only in animal foods. Vegans can meet their needs by eating foods like B12-fortified soy milk and fortified cereal, or by taking a vitamin pill.

Two other vitamins—riboflavin and vitamin D—tend to be low in vegans, since dairy foods are the main source in the American diet. For riboflavin, vegans should include lots of dark-green leafy vegetables and whole or enriched grains. Vitamin D isn’t found in plant foods, but it isn’t needed in the diet if the body makes enough through adequate skin exposure to sunshine. Riboflavin and vitamin D are also found in fortified cereals and can be taken as vitamin pills.

Vegan diets tend to be low in calcium, iron, and zinc. One problem can be the form of the mineral, e.g., iron in plant foods is non-heme iron, which is poorly absorbed as compared to heme iron in animal foods (Chap. 7). Also, high-fiber diets can hamper mineral absorption. For example, whole grains have phytic acid, and spinach and sesame seeds have oxalic acid. Both of these acids bind minerals and impede their absorption.

Good non-animal sources of calcium include fortified soy milk and soybean curd (tofu) processed with calcium sulfate. Iron in the diet can be increased by cooking (acid foods especially) in iron cookware and eating fortified cereals. Eating vitamin C-rich foods in the same meal increases the amount of iron absorbed from plant foods. Plant sources of zinc include legumes, whole grains, nuts, and tofu.

Strictly vegetarian diets can be nutritious when one is knowledgeable about nutrition and foods. People who choose to become vegans as adults (or choose this for their young children) need to take the time and care to acquire and use this knowledge. Pregnant or nursing women must take extra-special care to see that they meet their nutrient needs.

Infants born of vegan mothers and fed only their mother’s breast milk have suffered nerve damage from B₁₂ deficiency (Chap. 7). Some children on vegan diets have developed bone deformations from vitamin D deficiency.

Infants and toddlers are at higher risk of developing nutrient deficiencies on vegan diets for many of the same reasons given for protein and calorie deficiencies in low-income countries. They need more calories and nutrients, including protein, in proportion to their body weight than adults, and also need higher-quality protein. Growth retardation is often the first sign of malnutrition.

Lacto- and lacto-ovo-vegetarian diets are generally adequate in nutrients, except for iron and zinc. Milk is a good source of B₁₂, riboflavin, and calcium, and is usually fortified with vitamin D. However, milk and eggs are low in iron and zinc.

Good diets of all types tend to be those that include a variety of foods. Vegetarian diets exclude an entire group of food (meat), so variety is all the more important. Vegetarian diets can be very healthy—but not always. Some people eat a lot of cheese pizzas, ice cream, soft drinks, french fries, pastries, candy, etc., and call themselves vegetarians because they don’t eat meat. There are more than a few “vegetarians” who don’t like vegetables!