The health benefits of soybeans are legion, but too much of the food may have a downside.
A new study finds that large doses of the estrogenlike hormones that occur naturally in soybeans weaken the immune systems of mice. The finding has yet to be proven relevant to people, but soy's widespread use makes the finding worthy of further investigation, some researchers say.
Most U.S. infants either are breastfed or receive cow's-milk-based formulas, but about 25 percent are fed soy-based formulas. Some postmenopausal women take soy-derived supplements. These products contain substantial quantities of plant estrogens, such as genistein. Soy-fed infants may ingest 10 times as much genistein per kilogram of body mass as do adults on high-soy diets