Soy: Not Just Tofu Anymore
Remember when tofu and soy milk were virtually the only sources of soy? No more. These days, soy is a common ingredient in a host of foods, including breakfast cereals, bread, chips, frozen dinners, margarine, meatlessburgers, desserts, water-packed canned tuna and even chocolate bars.
Is that too much of a good thing?
That's a question some nutritionists are asking as the Food and Drug Administration (FDA) considers a petition to grant soy products a qualified health claim for possible prevention of breast, colon and prostate cancer. Unlike full-fledged health claims, qualified health claims are based on emerging research that suggests, but doesn't prove, a health benefit. Nuts, olive oil and omega-3 fatty acids are some of the foods and dietary supplements that have received qualified claims in recent years.
Soy protein has already earned one full-fledged FDA health claim for heart benefits. Since 1999, low-fat, low-cholesterol products containing at least 6.25 grams of soy protein per serving--equal to about a half-cup of tofu or a cup of soy milk--can carry a label that says: "Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease."
Since that claim went into effect, consumption of soy protein has more than doubled in the United States. If the new health claim is granted and soy consumption again doubles, industry sources project that U.S. soy intake could reach 4.5 grams per day -- or about half the daily amount consumed in Japan. That level "appears reasonable and presents no safety concerns," said the Solae Co., a soy protein research company, in petitioning the FDA for the new claim. But others are less sure.
Not only is soy a rich source of protein, it also contains complex carbohydrates that are less likely than processed products like white bread to send blood sugar soaring and boost insulin production. Soy has fiber, healthy fat and folic acid -- good for heart health and a protection against such birth defects as spina bifida. Soy also appears to help preserve bones and build muscle, and it can help lower blood pressure and blood cholesterol.
But it's the isoflavones in soy that may be of greatest benefit -- and concern. These substances have some of the same chemical properties as the female hormone estrogen.
Studies suggest isoflavones may offer some protection against breast, colon and prostate cancer in adults. But in laboratory and animal studies, isoflavones have been shown to affect immune function, the thyroid and sexual maturity. That's why in July, the Israeli Ministry of Health announced plans to recommend that young children limit soy products and advised that infants avoid them altogether. The French government recently recommended that soy products not be given to children under 3 to help minimize any risk from isoflavones.
In some quarters, these moves have been met with criticism.
"Soy really has some health benefits, and I think that it is absurd to suggest that soy should not be consumed by children," said Kenneth Setchell, professor of pediatrics at the Cincinnati Children's Hospital and a longtime researcher of soy proteins in animals and people.
A recent review of the health effects of soy infant formulas conducted by researchers at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., could find no ill effects from soy infant formula. Theoretically, soy-fed infants appear to be exposed to enough soy compounds to reach "pharmacologically active" levels, writes Aimin Chen and Walter J. Rogan in the 2004 Annual Review of Nutrition. But there is no indication that those levels have caused any problems in the 50 years the formulas have been used.
As the debate continues, here's what experts say to keep in mind when choosing soy products: