Soy Does a Body Good
Eating soy-based foods is one of the simplest things you can do for your health. High in protein, low in fat, and packed with isoflavones, soy can lower cholesterol and protect against heart disease, and there may be a host of other benefits as well.
By March 1, 2001 - last reviewed on June 9, 2016published
In recent years, psychologists and other health professionals have made us realize that our health depends largely on our behavior. Eating soy, it now appears, is one of the simplest things we can do to boost our health.
Once revered as a sacred crop in China, soybeans are one of the richest plant sources of protein. In fact, the World Health Organization considers it on par with meat and dairy proteins. But not only is this low-fat dietary protein great news for vegetarians or dieters, a growing body of research indicates that soy may help prevent many chronic diseases. Many of its therapeutic benefits are believed to come from its vast stores of isoflavones. These bioactive plant chemicals function like weak estrogen -- a female hormone necessary for normal growth and development -- by adjusting the hormone's effects when levels are too high or low.
To get the most out of soy, health experts suggest eating whole foods like tofu, soymilk and tempeh because they contain higher levels of isoflavones than processed foods or supplements. Fortunately, there are now a variety of soy and tofu products that are both convenient and tasty. Soymilk can be found nationally in refrigerated sections of supermarkets, and it easily replaces cow's milk for both drinking and cooking.
The biggest news is that soy lowers cholesterol and protects against heart disease. An analysis of 38 studies published in the New England Journal of Medicine found that eating soy lowers total levels of cholesterol by 10% and LDL or "bad" cholesterol by 13%. In 1999, the FDA gave soy the green light, stating definitively that eating 25 grams of soy protein each day as part of a low-fat, low-cholesterol diet reduces the risk of heart disease. Recently, the American Heart Association revised its dietary guidelines to recommend soy as part of a heart-healthy diet.
While research on other diseases isn't yet conclusive, scientists believe that soy may also help with the following:
OSTEOPOROSIS: A 1998 study published in the American Journal of Clinical Nutrition found that postmenopausal women who ate 40 grams of soy protein a day significantly increased the bone density in their spines. And a University of Iowa study found that women who consumed soy with isoflavones maintained bone density, while those who didn't consume isoflavones actually lost bone density. "The isoflavones in soy are identical to a drug called Ipriflavone, a synthetic isoflavone used for bone loss, so there's reason to think that isoflavones will do something for bone health," says Mark Messina, Ph.D., an adjunct associate professor of nutrition at Loma Linda University in California and former program director for the National Cancer Institute (NCI). "In general, if you substitute soy for animal protein, you'll lose less calcium from your bones because animal protein causes calcium loss."
MENOPAUSE: Although some studies suggest that soy isoflavone pills are no more effective than a placebo in fending off menopausal symptoms like hot flashes and night sweats, several other studies suggest otherwise. A 12-week-long Italian study found that postmenopausal women taking soy containing 76 mg of isoflavones experienced a 45% reduction in their symptoms, while those taking placebos reported only a 30% reduction. And a study of 177 menopausal women presented at the Third International Symposium on the Role of Soy in Preventing and Treating Chronic Disease found that those who took 50 mg of soy isoflavones had fewer and less severe hot flashes and night sweats than those who didn't take isoflavones.
"Soy won't make hot flashes and night sweats go away, but it will make them milder and slightly less frequent," says Gregory Burke, Ph.D., chairman of the Department of Public Health Sciences at Wake Forest University School of Medicine in North Carolina. "And that may be enough for many women."
CANCER: According to the NCI, soy is believed to coax cancerous cells to revert to normal. It may also prevent tumors from obtaining nutrients and block free radicals -- compounds that normally attack bacteria and viruses -- from damaging healthy cells. "There are several potent anti-cancer compounds in soy," says Clare Hasler, Ph.D., executive director of the Functional Foods for Health program at the University of Illinois. "I suspect that when the ongoing trials are completed, we'll see that soy may protect against cancer." Because of its estrogenic properties, soy appears most effective against hormone-related cancers like prostate and colon. Another study presented at the same symposium on soy found that soy reduced tumors by 40% to 60% in mice with prostate or bladder cancer.
Epidemiological studies suggest that soy also protects against breast cancer, and researchers often point to Japan and China where soy consumption is high and breast cancer rates are low. Even so, scientists recently discovered that, because consuming soy promotes breast cell growth, doing so later in life may actually raise the risk of breast cancer for postmenopausal women with a personal or family history of the disease. To play it safe, consult your doctor if you're at risk for breast cancer.
For those who want to stock up on soy, now's the time. April is National Soy Foods Month, and supermarkets typically carry a wide variety of soy foods like soy nuts, snack bars and instant shakes, all ready to grab on the go. One easy -- and satisfying -- way to include 25 grams of soy protein in your daily diet is to down a shake made with instant soy protein powder. Other convenience foods like soy-based burgers, hot dogs, deli meats and bacon have a taste and texture that's very similar to real meats. So this April, think health and think soy.