The soybean has been a known health food for centuries. Recognized early as a low-saturated-fat, high-fiber and highly bioavailable
source of protein, it's also an eco-friendly and eco-versatile plant easy to grow in a wide range of climates.
Lately, however, the positive relationship between soy and health has been challenged by the American Heart Association (AHA). And, because phytoestrogens in soy are analogs of human estrogen, there are reports of negative associations with breast cancer and hormone imbalances. But "sound-bite science" stories shouldn't keep you from enjoying soy's substantial health properties. While it may not be a proven miracle cure for heart disease or cancer, it is certainly a nutritious food that can contribute significantly to good health.
The most investigated compounds in soy are isoflavones, which research connects to a wealth of potential health assets. For women's needs, this includes stronger bones via influencing bone mineral retention and bone density, enhanced arterial health and relief from menopause-related hot flashes. Recently, it was determined the iron in soy is more bioavailable than previously believed. In men, isoflavones could possibly help reduce risk of prostate cancer.
For all, other health advantages abound. "Soy protein modestly lowers cholesterol, soy foods are great sources of high-quality protein while low in saturated fat. And soy is a good source of fiber, which further reduces cholesterol," says Mark Messina, PhD, director of Nutrition Matters, Inc., and one of the world's leading experts on soy and health. "New data suggest soy may also lower blood pressure and mitigate other risk factors for heart disease."
Soy Foods also are good choices for people with diabetes because of their low glycemic index. Most exciting, however, is research showing that as little as one serving of soy per day during childhood and/or adolescence may substantially reduce breast cancer risk later in life.
Soy Myths and Facts
In 2007, the AHA petitioned the Food and Drug Administration (FDA) to revoke approval of labeling soy products as helping reduce risk of coronary heart disease. At issue were the results of prospective studies concluding the net effect of regularly including soy in the diet amounted to no more than a few percentage points reduction in cholesterol. (Curiously, other ingredients approved for similar health claims boast comparable levels of activity.)
But AHA contradicts its own advice: that for every percentage point we reduce dietary cholesterol we get double or greater the reduction in cardiovascular disease risk. Studies show soy protein lowers LDL-cholesterol 3 to 5 percent. This equates to around 10 percent reduction in heart-disease risk–definitely a number you can live with. Plus, you get displacement effects when soy is substituted for high-saturated fat foods.
Another recent aspersion against soy is that it causes breast enlargement in men. However, this was based on a single case of one man drinking nearly a gallon of soymilk daily. "Contrary to what's often presented in the popular media, clinical studies show soy doesnâ€™t affect reproductive hormone levels–estrogen or testosterone–in men," says Messina.
Soy also has raised concerns of possible negative effects for some women, such as breast cancer patients. "But," adds Messina, "recently conducted epidemiologic studies suggest soy food intake after diagnosis either has no effect on, or actually improves prognosis."
David Feder. R.D. is director of S/F/B Communications Group, a national co-operative of food, health and nutrition experts.