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Soytainly!

The humble soybean may get a boost from the FDA. SHould you make room for it in your diet?

April 26, 1999|ROSIE MESTEL | TIMES HEALTH WRITER

Trundling by the tofu, meandering by the miso or sauntering by the soy milk in the supermarket later this year, we may spot something new: grocery labels telling us that soy foods could be good for our hearts.

That's if the Food and Drug Administration allows certain foods to carry claims that soy protein--as part of a diet low in saturated fat and cholesterol--helps fight coronary artery disease. The agency gave tentative approval in November to a proposal that would allow marketing claims to be made about soy's role in reducing the risk of heart disease. After a review of public comments, the FDA is expected to announce a final ruling by the end of October.

Soy protein, it appears, helps lower blood cholesterol, especially the bad, or LDL, cholesterol. It does so not only in people with high cholesterol but also--to a lesser extent--in people whose levels are in the "normal" range. Thus, given the link between cholesterol and heart disease, soy could help protect people against the nation's No. 1 killer.

Those in the soy business, not surprisingly, are delighted by the FDA's proposal. Pleased, too, are many scientists who study the effects of this bean on our bodies, not only on heart disease but also on breast and prostate cancer, osteoporosis and menopausal symptoms like hot flashes.

"The [FDA] proposal is very reasonable, based on what we know," says Stephen Barnes, professor of pharmacology and toxicology at the University of Alabama at Birmingham. "The knowledge about the effects of soy on cholesterol dates back over 20 years."

Yet some soy scientists also have misgivings about details of the FDA proposal.

They point to mounting evidence that only some kinds of processed soy proteins--those containing chemicals known as isoflavones--can do the cholesterol-lowering trick. These small chemicals, which are abundant in soy, are thought to mimic some of the beneficial actions of the human hormone estrogen, without mimicking bad ones, such as an increased risk of breast cancer. The FDA's proposal makes no such distinction.

"I think this is a mistake," says Mary Anthony, a cardiovascular epidemiologist working in the lab of Thomas Clarkson, a researcher at Wake Forest University School of Medicine in Winston-Salem, N.C. "If all soy protein is allowed to carry the health claim, you could be lumping together something that has little benefit with something that is likely to have a good benefit. And people won't be able to tell the difference."

The FDA, for its part, says there isn't enough evidence yet to single out isoflavones as the agent that lowers cholesterol. FDA officials have received comments, though, on the isoflavone issue--and could still change their minds.

Never mind the red tape. What about us? Should we eat soy? In what form? And how much?

First it's worth reviewing the evidence for soy's health benefits. Dozens of small studies in people, and many in animals, support its role in lowering cholesterol. The general gist of such research: Give people a diet with a certain amount of soy protein--25 grams or more, usually--in the form of textured vegetable protein, soy milk, flour, powder, whatever. Keep them on that diet for several weeks or months, and then compare their blood cholesterol with a group of people who got the same amount of protein in another form, such as casein, derived from cow's milk.

The studies found that levels of "bad" cholesterol dropped significantly, with the biggest changes seen in people with very high cholesterol counts to begin with. In some studies good HDL cholesterol levels rose too.

There are other studies suggesting that the protein, or the isoflavones it contains, may help ward off heart disease in other ways: by increasing the stretchiness of the arteries in our bodies, so we're less likely to have a heart attack; and by preventing cholesterol from being "oxidized," a bad-news chemical change that speeds plaque buildup. Given this, it's not surprising that the coronary arteries of monkeys on soy diets don't clog up with plaque as quickly.

In other words, the cholesterol-lowering effect of soy has been pretty well-documented. But there are other tantalizing possibilities: that soy may help reduce bone loss in postmenopausal women, and reduce the severity of hot flashes.

Comparisons With Diets in Asia

Soy might even help ward off breast and prostate cancer. Countries where soy intake has been traditionally high, such as Japan and China, have had lower levels of these diseases, points out Anna Wu, professor of preventive medicine at USC. And there are some studies suggesting that women who eat more tofu are at lower risk for breast cancer. "We're still in the early stages of trying to sort out if there is an effect, what the effect is, and how it's being exerted," Wu says.

Given the FDA's proposal, it's no wonder that people in the soy processing business are anticipating expanding into new markets, as their nutritionists experiment with new soy delicacies.

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