Thursday, June 19, 2008

Ask the Expert: As a vegetarian, am I getting the right vitamins and minerals?

Q. As a vegetarian, am I getting the right vitamins and minerals?

A. First of all, it is important to define what a “vegetarian diet” actually is. Are you eating a vegan diet, which excludes all animal products including dairy and eggs? Or are you on a lacto-ovo-vegetarian diet which does incorporate dairy products and eggs while excluding meat, fish, and poultry? It is important to realize what is missing from your diet before deciding on what nutritional supplements to take. The American Dietetic Association recommends eating a wide variety of foods, including whole grains, fruits, vegetables, beans, seeds, nuts, and dairy and eggs (the last two only if not on a vegan diet). In terms of possible vitamin deficiencies, the iron from plant sources is more poorly absorbed than that found in animal products, but the higher levels of vitamin C found in vegetarian diets may help increase iron absorption. Studies have shown that iron deficient anemia is not more common in vegetarians, so iron supplementation is probably not necessary.

Vegetarians should be sure to include foods rich in vitamin B12 (fortified cereals or soymilk, meat substitutes, or nutritional yeast) or take it as a supplement, since studies have shown that they have low blood levels of this vitamin. There is even a case of a 33 year old man who had been on a strict vegan diet since the age of 20 who presented with severe nerve damage in both eyes due to vitamin B12 deficiency. He had never taken any supplements. Even after he was given vitamin B12, the nerve damage did not improve. Therefore, it is important to be conscious of the need for adequate dietary or supplemental vitamin B12 intake if one is on a vegetarian diet, especially as one ages when absorption of this vitamin decreases.

If one does not drink milk, then vitamin D levels may also be deficient, as fortified milk is the most common dietary source of vitamin D. As long as there is adequate strong sunlight exposure (at least 15 minutes of sunlight on the upper extremities and face every day), supplementation should not be necessary. However, there are vegetarian products such as soymilk that are fortified with vitamin D that can be consumed if sunlight exposure is inadequate. Calcium is a mineral that usually is not deficient in vegetarians who eat calcium rich dairy products or calcium-rich vegetarian foods (i.e. tofu, beans, green, leafy vegetables). Vegans should make sure they get the daily recommended requirements for calcium from their diets, and if they do not, they should take a calcium supplement. The other two nutrients that the American Dietetic Association advises vegetarians to be aware of are zinc and linolenic acid. Zinc levels in vegetarians tend to be lower than in non-vegetarians, so it is a good idea to make sure to eat enough zinc-rich foods (whole grains, legumes, corn, tofu) to meet or exceed the daily recommended requirement. Linolenic acid is an essential fatty acid found in fish or eggs. If these foods are not consumed, it is important to include other linolenic acid-containing foods in the diet, such as walnuts, flaxseed oil, soybeans, and canola oil. In general, a healthy vegetarian diet should include up to three servings of calcium rich foods, 2-3 servings of legumes, nuts, eggs, and meat substitutes, 3-5 servings of vegetables, 2-4 servings of fruit, 6-11 servings of grains, and sparing use of fats, oils, and sweets.

Q. Is soy milk a good source of calcium?

A. When choosing a brand of soy milk, it is important to select one that is calcium (and ideally Vitamin D) fortified, as soy milk itself is not rich in calcium. However, even when fortified, soy milk contains less calcium than regular milk. Eight ounces of skim milk contain 300 mg of calcium, while eight ounces of calcium fortified soy milk contains about 200 mg. Unfortified soy milk can contain much less calcium. Another soy product, tofu, usually has more calcium than soy milk depending on how it is processed. One method of making tofu involves the addition of calcium sulfate to the processed soy beans in order to solidify the bean mixture. One should look for calcium sulfate in the ingredient list in order to buy tofu with the highest calcium content. If a person wants to replace cow’s milk with soy milk, it is important to consume more to make up for the reduced calcium content, or add other calcium-rich foods or calcium supplements to the daily diet. In 1997, the Institute of Medicine released new recommendations for recommended calcium intake: 1300 mg for people aged 9-18 years and pregnant women under 19 years of age, 1000 mg for those aged 19-50 years including pregnant women over 19, and 1200 mg for those over fifty-one. These recommendations should be kept in mind when one seeks to replace dairy products with other foods, in order to ensure adequate calcium intake on a new diet.

No comments: