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How Much Soy Isoflavones Per Day?

Jul 28, 2011 | By Stephen Christensen
How Much Soy Isoflavones Per Day?
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Isoflavones are organic molecules produced by plants, such as soy, wild yam, red clover and kudzu. Isoflavones act as antioxidants in the tissues of their parent plants, and they may confer some protection from grazing animals by altering these predators' reproductive activity. In your tissues, isoflavones mimic some of the activities of your own estrogen, earning them the nickname, "phytoestrogens." Soy isoflavones -- genistein and daidzein -- have received a great deal of scientific scrutiny for their potential use in human medicine. Ask your doctor if soy isoflavones are appropriate for you.

Menopause

For decades, doctors have prescribed hormone replacement therapy, or HRT, to reduce the hot flushes, vaginal dryness, mood changes and other symptoms associated with menopause. However, in 2003 a large clinical trial was prematurely halted when researchers discovered that HRT increased a woman's risk for heart disease and breast cancer. Subsequently, many women turned to soy isoflavones as a presumably safe alternative to HRT. Although the results of clinical trials are conflicting, a study published in the March 2009 issue of "Menopause" demonstrated a reduction in hot flushes among women who took 54 mg of genistein daily for 12 months.

Osteoporosis

One of HRT's principal benefits is its ability to preserve bone mass in postmenopausal women, delaying the development osteoporosis and reducing the risk for bone fractures. In 2002, scientists at Italy's University of Messina demonstrated that daily consumption of 54 mg of genistein for 12 months prevented loss of bone mass in postmenopausal women. A March 2010 review in "Journal of Osteoporosis" indicates that daidzein, the other principal isoflavone in soy, may be even more effective than genistein for preserving your bone mass.

Dosages

Dr. Duane Townsend, author of "A Maverick of Medicine Speaks to Women," is an avid supporter of soy isoflavone use among women who suffer from premenstrual syndrome, menopausal symptoms and other disorders of hormonal imbalance. He recommends that women begin with isoflavone doses that are equivalent to what Asian women consume in their diets: 35 mg of genistein daily along with 3 to 5 mg of daidzein. Many supplements combine these two isoflavones. You may need to double your dosage if your symptoms do not subside.

Considerations

Soy isoflavones exert estrogen-like effects in your tissues. This has raised concerns about the safety of these compounds in women at risk for breast cancer or other estrogen-sensitive malignancies. Although some studies indicate soy products are safe, even in women already diagnosed with breast cancer, not all physicians are comfortable recommending them to their patients. The optimal dosage of soy isoflavones for different conditions has not been established, but 35 to 70 mg of genistein daily, combined with 3 to 7 mg of daidzein, appears to be useful for most women. Seek medical advice before adding soy isoflavones to your daily regimen.

References

Article reviewed by Eric Lochridge Last updated on: Jul 28, 2011

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