Magazine article Science News

Nutritionists Debate Soy's Health Benefits

Magazine article Science News

Nutritionists Debate Soy's Health Benefits

Article excerpt

The simple soybean is turning into one of nutrition's biggest puzzles.

Scores of presentations at the Experimental Biology '99 meeting this week in Washington, D.C., examined the relationship between soy products and cancer. In almost all cases, the researchers agree, soy seems to be a cancer fighter. However, a soybean component that has been touted for its health benefits is not living up to expectations. For postmenopausal women, the story may be even more complicated.

Reaffirming soy's potential health value, several studies at the conference reported that diets rich in the legume protect rats against colon cancer, breast cancer, and prostate cancer. Moreover, men who ate 39 grams of soy protein each day for 1 year had fewer colon cells in the process of dividing than did men who didn't eat soy, reports Deepa Thiagarajan of Michigan State University in East Lansing. With fewer cells proliferating, the men stand a better chance of avoiding colon cancer, she says.

Soy compounds called isoflavones mimic the hormone estrogen. These soy constituents might disrupt hormone-dependent cancers, such as many prostate and breast cancers, scientists have reasoned (SN: 10/11/97, p. 230).

More than 100 companies sell supplement pills or foods fortified with genistein, one of the most hyped isoflavones, says nutrition consultant and author Mark Messina of Port Townsend, Wash.

In one new study, genistein slowed the growth of human prostate tumors grafted into rats, reports Jin-Rong Zhou of Beth Israel Deaconess Medical Center in Boston.

However, unlike complete soy, genistein alone does not protect mice from breast cancer, says Ruth S. MacDonald of the University of Missouri-Columbia. Even more troubling, Maurice R. Bennink of Michigan State University finds that adult rats fed genistin, which is metabolized into genistein, are more likely to develop colon cancer than those fed standard diets. …

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