Vegetarians and health enthusiasts have known for years that foods rich in soy protein offer a good alternative to meat, poultry, and other animal-based products. As consumers have pursued healthier lifestyles in recent years, consumption of soy foods has risen steadily, bolstered by scientific studies showing health benefits from these products. Last October, the Food and Drug Administration gave food manufacturers permission to put labels on products high in soy protein indicating that these foods may help lower heart disease risk.

     As with health claims for oat bran and other foods before it, this health claim provides consumers with solid scientific information about the benefits of soy protein and helps them make informed choices to create a "heart healthy" diet. Health claims encourage food manufacturers to make more healthful products. With soy, food manufacturers have responded with a cornucopia of soy-based wares.

     No sooner had FDA proposed the health claim regulation, however, than concerns arose about certain components in soy products, particularly isoflavones. Resulting questions have engulfed the regulation in controversy.

     This came as no surprise to Elizabeth A. Yetley, Ph.D., lead scientist for nutrition at FDA's Center for Food Safety and Applied Nutrition . "Every dietary health claim that has ever been published has had controversy," she says, "even the relationship of saturated fat to a healthy diet."

     While the controversy may seem confusing to the consumer giving it casual consideration, a careful review of the science behind the rule reveals a strict divide between what FDA allows as a health claim based on solid scientific research and related issues that go well beyond the approved statements about health benefits of soy protein.

     What's known is that all foods, including soy, are complex collections of chemicals that can be beneficial for many people in many situations, but can be harmful to some people when used inappropriately. In that simple fact lies much of the scientific dilemma--when do data show a food is safe and when do they show there could be problems?

     Scientists agree that foods rich in soy protein can have considerable value to heart health, a fact backed by dozens of controlled clinical studies. A yearlong review of the available human studies in 1999 prompted FDA to allow a health claim on food labels stating that a daily diet containing 25 grams of soy protein, also low in saturated fat and cholesterol, may reduce the risk of heart disease.

     "Soy by itself is not a magic food," says Christine Lewis, acting director of the Center for Food Safety and Applied Nutrition's Office of Nutritional Products, Labeling and Dietary Supplements. "But rather it is an example of the different kinds of foods that together in a complete diet can have a positive effect on health."

     Much of the research to date has examined dietary soy in the form of whole foods such as tofu, "soymilk," or as soy protein added to foods, and the public health community mostly concurs that these whole foods can be worthwhile additions to a healthy diet. The recently raised concerns, however, focus on specific components of soy, such as the soy isoflavones daidzein and genistein, not the whole food or intact soy protein. These chemicals, available over the counter in pills and powders, are often advertised as dietary supplements for use by women to help lessen menopausal symptoms such as hot flashes.

     The problem, researchers say, is that isoflavones are phytoestrogens, a weak form of estrogen that could have a drug-like effect in the body. This may be pronounced in postmenopausal women, and some studies suggest that high isoflavone levels might increase the risk of cancer, particularly breast cancer. Research data, however, are far from conclusive, and some studies show just the opposite--that under some conditions, soy may help prevent breast cancer. It is this scientific conundrum, where evidence simultaneously points to benefits and possible risks, that is causing some researchers to urge caution.

     Unlike the controversy surrounding soy isoflavones, available evidence on soy protein benefits is much clearer. That's why FDA limited its health claim to foods containing intact soy protein. The claim does not extend to isolated substances from soy protein such as the isoflavones genistein and daidzein.

     "The story's not all in yet," says Margo Woods, D.Sc., associate professor of medicine at Tufts University, who has studied soy's effects in postmenopausal women. "There's a lot of emerging data and it's confusing. In the meantime, we should be cautious." She says her concerns are centered mainly on isoflavone supplements and that she's "much more comfortable" recommending soy as a whole food. "There are probably hundreds of protective compounds in soy [foods]. It's just too big a leap to assume that a pill could do the same thing."

     Daniel Sheehan, Ph.D., director of the Estrogen Knowledge Base Program at FDA's National Center for Toxicological Research, also urges caution in consumption of soy isoflavones. In formal comments submitted to the public record of his own agency while FDA was reviewing the health claim, Sheehan, along with colleague Daniel Doerge, Ph.D., wrote, "While isoflavones may have beneficial effects at some ages or circumstances, this cannot be assumed to be true at all ages. Isoflavones are like other estrogens in that they are two-edged swords, conferring both benefits and risks."

     As a science-based agency, FDA recognizes that research information evolves with time and that some of the existing confusion will be resolved as new studies are completed. "We continue to monitor the ongoing science," Yetley says. "As new data warrants, we make adjustments in our position and the advice we give to the public. We take this responsibility very seriously."

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Information taken from the U. S. Food and Drug Administration
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