The argument over soy
THESE days, soy goes far beyond the traditional soy milk and tofu. Breakfast cereals, bread, chips, frozen dinners, margarine, meatless burgers, desserts, canned tuna and even chocolate bars are just some of the popular foods that often contain soy.
But is it too much of a good thing?
That’s a question asked by some as the Food and Drug Administration considers a petition to give soy products a new boost: 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 points to, but doesn’t prove, health benefits. 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 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 half a 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 soy intake could reach 4.5 grams per day -- or about half the daily amount consumed in Japan. That 4.5 level appears reasonable and presents no safety concerns, contends the Solae Co., a soy protein research company, in petitioning the FDA for the new claim.
Not only is soy a rich source of high-quality protein, but it also contains complex carbohydrates that are less likely to send blood sugar soaring and boost insulin production than simple carbohydrates. Soy has fiber, healthy fat and folic acid -- good for heart health -- and protects a fetus against such birth defects as spina bifida. Soy also appears to help preserve bones, build muscle and 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 help protect soy plants against insects and have some of the same chemical properties of the female hormone estrogen.
“Most of the safety issues pertain to infants and young children,” said Mark Messina, an adjunct associate professor of nutrition at Loma Linda University in California who consults with the soy industry. “With adults, it’s hard to find any cause for concern.”
Studies point to 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 to one a day and advised that infants avoid them altogether. The French government recently advised that soy products not be given to children younger than 3.
But a recent review at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., reached a different conclusion. Though the researchers found that soy-fed infants are exposed to enough compounds that are pharmacologically active, they concluded that “there is no indication of such action in the 50 years the formulas have been used.”
While the debate continues, here’s what experts say to keep in mind when choosing soy products:
* A little goes a long way. Messina says to aim for 15 to 25 grams of soy per day -- about the amount found in one-half to one cup of tofu or a couple of cups of soy milk. If you’ve got high blood cholesterol, “shoot for 25 grams per day,” he said, noting “the limitation is not based on any safety concerns, but the dietetic principle of eating a varied diet.”
* Soy foods are not always low in fat or calories. Half a cup of soy nuts has about 250 calories. Many soy cereals contain added sugar. An eight-ounce glass of soy milk packs four grams of fat and 100 calories -- about 20% more calories than a glass of skim milk. The good news: Soy has healthy fat.
* Go traditional. Roasted soy nuts, soy milk, tofu (a fermented bean curd); tempeh; miso soup and edamame (the immature, green soybeans that can be steamed or stir-fried), are mainstays in Asian countries, including Japan. Few, if any studies, show that such new products as soy bread, crackers and cookies have the same long-term benefits as traditional soy sources, although eating soy burgers and hot dogs seems to help in lowering blood pressure.
