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December 8, 1999
Soy Power: The Benefit of the Bean
By Elizabeth Smoots, M.D.

Simply put, soybeans are a powerhouse of good nutrition. They're cholesterol free, and they're rich in fiber and vitamin E. When substituted for meat, soy protein helps reduce the fat in your diet. And soybeans are packed full of all the essential amino acids found in animal protein -- the only vegetable that can make that claim.

Adding to its powerful punch, soy is the most plentiful source of natural plant hormones called phytoestrogens. One of these substances, an isoflavone called genistein, acts like a weak version of the female hormone estrogen. Like estrogen, genistein has a beneficial effect on the bones, brain, bladder, heart, and blood vessels. But studies indicate that unlike estrogen, genistein may help block the adverse effects of hormone activity on the breasts and on the prostate gland.

In Asian countries, where soy products containing plant estrogens are a dietary staple, there is a reduced incidence of several chronic ailments. Early research suggests the following health benefits of soy:

Heart disease. Consuming soy protein containing genistein regularly can help lower cholesterol about 10 percent, according to studies. Soy decreases both total cholesterol and bad (LDL) cholesterol and works to maintain healthy levels of good (HDL) cholesterol. It also helps prevent the formation of blood clots and arterial plaque, both of which increase your risk of suffering a heart attack or stroke.

Cancer. Scientists have known for years that countries where people consume soy products regularly have a decreased incidence of cancer of the breast, colon, and prostate. Currently, several U.S. studies are testing the effects of soy on the prevention of breast cancer and prostate cancer. Early data indicate that soy products may act to inhibit enzymes involved in the formation, growth, and spread of tumor cells.

Menopause. Further research is needed to determine soy's effect on the symptoms of menopause, and more studies are underway. Studies performed thus far indicate that soy's mild estrogen-like activity may ease menopausal symptoms; one study showed about a 45 percent reduction in hot flashes among menopausal women who consumed soy products regularly. Soy may help preserve an aging woman's memory and mental faculties as well. Scientists are studying soy as a possible natural alternative to hormone replacement therapy.

Osteoporosis. Preliminary research suggests that soy may be effective in both the prevention and treatment of menopausal bone loss in women. Some forms of soy, such as tofu, are also good sources of calcium, a mineral needed for strong bones.

Soy food


Tofu -- a spongy food made by curdling soy milk; absorbs the flavors of the foods it is cooked with

Firm: stir-fries, casseroles, and soups; soft: dips, dressings, and custards; silken: pureed or blended dishes

Tempeh -- a dense, chewy cake made from fermented soybeans

Often marinated, then grilled, steamed, or baked

Whole soybeans -- a bland legume best cooked with robust ingredients

Soups and casseroles; can be roasted as a snack

Soy milk -- a mixture of pureed soybeans and water; comes in flavored and nonfat varieties

Milk substitute used in shakes and baked goods and on cereal

Texturized vegetable protein (TVP) -- a dried, granular soy product

Ground-meat substitute used in burgers, soups, chili, tacos, and casseroles

Soy powder -- a concentrated food supplement

Fruit smoothies

Miso -- paste made from cooked, aged soybeans

Soups, sauces, marinades, and dips

Soy sauce (tamari) -- liquid condiment

Stir-fries, rice, and vegetable dishes

*Check labels for the amount of soy protein -- the part that contains the isoflavone genistein. Some soy products, such as soy sauce, have little or none.

More research is needed to determine the amounts of soy that are safe and optimal for various health conditions. Many authorities suggest that eating as little as one serving of soy protein a day may help preserve good health. A cholesterol-lowering effect may be achieved with 25 grams of soy protein a day given in divided doses, according to some studies. Until long-term effects are known, talk to your health care provider before consuming large amounts of soy supplements.

For recipes and answers to your soy questions, visit or call 1-800-TALKSOY.

Elizabeth Smoots is a family physician and medical writer in Seattle, Washington