Scientific Update
A Review of Recent Scientific Papers Related to Vegetarianism
By Reed Mangels, PhD, RD, FADA
Vegetarian Adults Get Plenty of Boron
Boron is a mineral which appears to be essential for humans. It seems to play a role in calcium metabolism and thus may be important for bone health. A recent survey showed that the highest median boron intakes by US adults were seen in adult male vegetarians. Female vegetarians also had intakes of boron which were higher than those of non-vegetarian women. The major contributors of boron for people in the US are coffee, cow's milk, apples, dried beans, potatoes, orange juice, peanut butter, wine, and apple juice. Foods which are especially high in boron are peanut butter, peanuts, nuts, and raisins.
Rainey, C.J., Nyquist, L.A., Christensen, R.E., et al. 1999. Daily boron intake from the American diet. J Am Diet Assoc 99:335-340.
Macrobiotic Diets and Vitamin B-12 Deficiency
Vegans typically get their vitamin B-12 from fortified foods or supplements. What happens when dietary vitamin B-12 is not adequate in early life? A recent study of Dutch teens who were on macrobiotic diets until they were six years old attempted to answer this question. The subjects were 73 teens who had followed a macrobiotic diet until they were six years old and then switched to lacto-ovo, lacto, or non-vegetarian diets. Despite having had dietary sources of vitamin B-12 for the past five or more years, the study subjects still had blood levels suggesting that their vitamin B-12 status was not normal.
The authors suggest that those whose diets are low in vitamin B-12 early in life may need a higher intake of vitamin B-12 later in life in order to achieve normal blood levels. Research is continuing on the implications of lower blood vitamin B-12 levels for psychomotor development. This study supports the need for a reliable, adequate source of vitamin B-12 throughout life.
van Dusseldorp, M., Schneede, J., Refsum, H., et al. 1999. Risk of persistent cobalamin deficiency in adolescents fed macrobiotic diet in early life. Am J Clin Nutr 69:664-671.
Which Foods Provide Soy Isoflavones?
Many studies suggest that soy products reduce cancer risk. Substances in soy products called isoflavones may play a role in cancer control. It is important to know which foods are good sources of soy isoflavones. The following foods were rated as important contributors of isoflavones: tofu, soy yogurt, tempeh, soy milk, low-fat tofu, soy flour, miso, soy protein isolate, low-fat soy milk, and veggie soy burgers.
Kirk, P., Patterson, R.E., Lampe, J. 1999. Development of a soy food frequency questionnaire to estimate isoflavone composition in US adults. J Am Diet Assoc 99:558-563.
For more information about isoflavone content of foods check out USDA's new Soy Isoflavone Database which provides values for major isoflavones in 128 soy foods and ingredients. It can be found on the web at: <http://www.nal.usda.gov/fnic/foodcomp/data/isoflav/isoflav.html>
Vegetarian Physicians
A study of close to 4400 US women physicians examined vegetarianism among this group. Eight percent of the physicians surveyed described themselves as vegetarians, although only 5% did not eat meat, fish, or poultry the week before completing the survey. Vegetarian-ism was most common in those age 40 to 49 years and among Asian-Americans. Physicians who described themselves as liberal were more likely to be vegetarian than those who described themselves as conservative. The specialty with the highest percentage of vegetarians was neurology; the lowest percentage was seen in ophthalmologists. The major reason cited for being a vegetarian were health reasons (69%), animal welfare (42%), and environmental concerns (32%).
White, R.F., Seymour, J., Frank, E. 1999. Vegetarianism among US women physicians. J Am Diet Assoc 99:595-598.
