Estrogen's effects on human health are not a new concern. Premarin, the first estrogen-containing pill, was released to the U.S. market in 1942. In 1966, Dr. Robert Wilson, a New York gynecologist, published "Feminine Forever," a book extolling the virtues of estrogen-replacement therapy. However, subsequent research linked estrogen therapy to uterine and breast cancers, and the Women's Health Initiative was discontinued in 2002 when it was discovered that study subjects who took estrogen were also at higher risk for ovarian cancers, heart disease and strokes. Many women have turned to soy to avoid the risks of estrogen.
Phytoestrogens
According to Dr. Duane Townsend, author of "A Maverick of Medicine Speaks to Women," several hundred plants are known to contain phytoestrogens, which are isoflavones that exert estrogen-like effects in your body. Townsend contends that soy is the premier source of high-quality phytoestrogens, and soy-based genistein is superior to other isoflavones for conferring health benefits in humans. Ostensibly, genistein's chemical properties allow it to balance your body's estrogen needs without the risks that accompany prescription hormones.
Estrogen Dominance
Regardless of your gender, many of the cells in your tissues contain receptors that respond to estrogen stimulation. Estrogen receptors regulate an array of physiologic responses in your body, and they play a role in the development of breast and prostate cancers. Townsend suggests that premenstrual syndrome, uterine fibroids, fibrocystic breasts, lack of libido and other hormonally mediated symptoms are caused by an excess of estrogen stimulation, otherwise known as estrogen dominance. Genistein occupies the same receptors that estrogen does, but it alleviates estrogen dominance because its effects are weaker.
Estrogen Deficit
One of the primary reasons women turn to hormone-replacement therapy -- or soy, for those who want to avoid the risks of hormones -- is menopause. As estrogen levels decline, so does the stimulation of cellular receptors in your tissues. This estrogen deficit leads to hot flashes, mood changes, vaginal dryness and other menopausal symptoms. Because genistein also binds to estrogen receptors, albeit less avidly, it reduces the troubling consequences of menopause for some women.
Breast Cancer
Soy isoflavones, particularly genistein, mimic some of the effects of estrogen in your body. The long-term safety of soy consumption is a matter of controversy, with some scientists asserting that isoflavones increase the risk of breast cancer. However, a 2011 Kaiser Permanente review reinforces earlier studies showing that soy is safe, even for women previously diagnosed with breast cancer.
Considerations
Although they have not been proved to cure or prevent any condition, soy isoflavones may offer benefits for individuals with issues of estrogen imbalance. Townsend recommends daily doses of soy isoflavones that are proportionate to the soy consumed in populations where breast cancer is uncommon: 35 mg of genistein, in addition to 3 to 5 mg of daidzein, the other principal soy isoflavone. Since isoflavones are rapidly metabolized and eliminated from your body, they must be consumed daily. If you are considering adding soy to your daily regimen, ask your doctor if it is appropriate for you.
References
- U.S. Food and Drug Administration: Conjugated Estrogens -- Letter from Dr. Janet Woodcock
- National Institutes of Health: NHLBI Stops Trial of Estrogen Plus Progestin Due to Increased Breast Cancer Risk, Lack of Overall Benefit; July 2002
- "A Maverick of Medicine Speaks to Women"; Duane Townsend, M.D.; 2003
- "Cancer Epidemiology, Biomarkers and Prevention"; Soy Food Consumption and Breast Cancer Prognosis; B.J. Caan, et al; February 2011
