A word of caution

American Fitness, March-April, 2003

Americans are sold on soy. Women, in particular, devour it in hopes it will quench the flame that ignites hot flashes--one of soy's biggest claims. However, can too much soy be harmful?

According to a study published in Obstetrics and Gynecology last March, a daily 100 milligram dose of soy isoflavone consumed for four months reduced hot flashes up to 25 percent. However, "you've got to eat a lot of soy to get that small incremental benefit," says Maida Taylor, M.D. To make a significant difference, she says, you'd have to eat about 160 grams of soy per day--about six to eight servings of silken tofu or 12 to 16 soy breakfast links.

Nevertheless, for women suffering from hypothyroidism (i.e., underactive thyroid), this would be about five to seven servings too many. According to Richard Shames, M.D., a general practitioner in Boca Raton, Florida, and author of Thyroid Power (HarperCollins, 2001), genistein in soy apparently blocks the action of iodine and tyrosine in the production of thyroid hormone. "This effect is dose related. In other words, if you eat a modest amount of this otherwise healthy food, your thyroid will not be bothered."

Soy isoflavones in pill form, touted to alleviate menopausal symptoms, rack up $20 million in sales. They are popular, explains Taylor, because purchasing a nutritional supplement gives a feeling of autonomy and control over one's health and is perceived as totally safe. This is not true, says Taylor. "It's another one of those data-free zones," she explains. "More research is needed." According to James W. Anderson, M.D., a professor of medicine and clinical nutrition at the University of Kentucky in Lexington, "Soy isoflavones are oversold and excessive quantities may be hazardous."

The bottom line, according to Alice Lichtenstein, D.Sc., a professor of nutrition at Tufts University in Boston, is not to over-do soy supplements. For now, "it's best to use soy as a whole food."

For more information, visit:

* FDA's Talk Paper on Soy: http:/vm.cfson/fda.gov/~lrd/tpsoypr2.html

* Soy Info Online: www.soyinfo.com

* American Soybean Association: www.amsoy.org

* Soyfoods Association of North America: www.soyfoods.org

* United Soybean Board: www.talksoy.com.