Westerners have been slow to put tempeh, soy milk, tofu, and other soybean products on the table. But as evidence mounts that compounds in soy isoflavones have impressive health benefits, so too does consumption of this Asian dietary staple.
Soy isoflavones are powerful plant substances chemically similar to the female hormone estrogen. Their presence in soy foods may help to explain why people in countries where soy is a big part of the diet suffer from relatively few menopausal symptoms such as hot flashes. It may also explain why rates of certain hormone-related cancers are much lower in Asia than they are in many parts of the West, including the United States.
While soy isoflavones are now available in supplement form, it remains to be determined whether these pills can provide the same health benefits as soy isoflavones consumed as part of the diet. In fact, most research has been done on people who eat soy products rather than take soy supplements. It's possible that isoflavones are just one of several therapeutic compounds in soy.
Health Benefits
Two particularly important isoflavones in soy genistein and daidzein appear to protect against hormone-related disorders such as breast cancer and endometriosis. They do this by competing for the same place on cells (receptor sites) that the body's own estrogen does. Some of the risks of excess estrogen, including breast and uterine cancer, can apparently be lowered in this way.
Similarly, when the body's natural levels of estrogen drop, as they do with menopause, soy isoflavones can compensate by binding to some of the cell receptor sites that estrogen once did. Menopausal symptoms may improve as a result.
Research findings suggest that soy isoflavones may also inhibit cancer-causing enzymes, provide antioxidant protection, and enhance the immune system.
Specifically, soy isoflavones may help to:
Control symptoms of menopause and perimenopause. When regularly ingested, soy may reduce the frequency and severity of hot flashes and other menopausal difficulties. In one study, women who added 45 grams of soy flour to their daily diet experienced a 40% reduction in hot flashes. The isoflavones in soy are believed to be responsible for these effects.
Guard against osteoporosis. Soy isoflavones may aid women (and men) in maintaining bone mineral density. One study of postmenopausal women found that consuming 40 grams of soy protein a day resulted in a significant increase in bone mineral density in the spine, an area often weakened by osteoporosis. If the spine is weak, stooped posture and myriad complications may develop.
