Benefits of Soy

Last Updated: May 1, 2003

The decrease in estrogen production that signals menopause can produce a variety of symptoms. These include night sweats and hot flashes. However, the severity of menopause symptoms varies throughout the world. For example, Asian women are typically one-third as likely as American women to report symptoms. Although, to some extent, this may reflect cultural differences regarding willingness to discuss these symptoms, there appears to be an actual difference in the severity and incidence of symptoms.

Soy consumption has been proposed as one explanation for these differences. The estrogenic activity of soybean isoflavones may help to offset the effects of reduced estrogen production by the ovaries. Most important, in a recent Australian study, researchers found that women who consumed 45 grams of soy flour per day experienced a 40% decrease in menopause symptoms. Several studies examining the effects of soy on menopause symptoms are under way.

Reducing hot flashes
The hormonal changes that occur during menopause can cause a variety of symptoms including: hot flashes, night sweats, insomnia, vaginal dryness and headaches. Researchers have explored the question of whether consumption of soy with its weak, estrogenic properties, can reduce the number and severity of hot flashes. The results are inconclusive. Further studies are needed to clarify the role of soy in reducing the hot flash symptoms.

Cardiovascular effects
Since 1999, the U.S. Food & Drug Administration has allowed foods containing at least 6.25 grams of soy protein to claim that they reduce the risk of coronary heart disease. As part of a low saturated fat diet, 25 grams of soy protein per day can result in significant cholesterol reduction, according to the FDA. When comparing soy protein with and without isoflavones, studies found a decrease in total cholesterol and LDL cholesterol with increasing isoflavone dosage. These effects are similar to those of estrogen, but soy isoflavones do not increase HDL cholesterol or triglycerides.

In addition to lowering cholesterol, soy may lower cardiovascular risk in other ways. It may improve the function of cells that line the inside of arteries and it may decrease the formation of blood clots.

Protecting your bone health
Soy may help prevent osteoporosis. Because soy inhibits a substance called tyrosine kinase, it may offer bone effects beyond that of estrogen. However, studies have been relatively small and brief. Studies of two to three years are needed to evaluate bone-protecting effects.

Dose and drug interactions
The recommended daily dose to lower cholesterol is 25 grams of soy protein. To prevent osteoporosis, 40 grams per day is recommended. To treat osteoporosis and prevent hot flashes, 60 grams of soy protein per day is recommended.
According to the U.S. Soy Foods Directory of the Indiana Soybean Board, the following foods are excellent sources of isoflavones, providing a range of 30-50mg per serving.
- Roasted soy nuts (1 ounce)
- Soy flour (1/2 cup)
- Soy grits (1/4 cup)
- Textured soy protein (1/2 cup, cooked)
- Yellow, green vegetable or black soybeans (1/2 cup, cooked)
- Regular soymilk (1 cup)
- Tempeh (1/2 cup)
- Tofu (1/2 cup)

Be sure to tell your doctor if you are taking any kind of dietary supplement, including soy.

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