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Estrogen Metabolism Affected by Supplemental Isofl

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From http://www.medscape.com/viewarticle/429873?srcmp=wh-031502


Estrogen Metabolism Affected by Supplemental Isoflavones



NEW YORK (Reuters Health) Mar 11 - Results of a recent study suggest that supplemental soy isoflavones alter the steroid hormone concentrations and menstrual cycle length in premenopausal women. The risk for breast cancer may therefore be reduced by these supplements, according to researchers.

Dr. Nagi B. Kumar and colleagues from the University of South Florida, Tampa, examined whether supplemental isoflavones produce a change in steroid hormones and menstrual cycle length in premenopausal women without breast cancer. Sixty-eight women between the ages of 25 and 55 years were randomized to receive either the soy supplement of genistein at 40 mg per day or placebo over 12 weeks.


The researchers assessed changes in the patients' anthropometric, nutritional, and hormonal biomarkers from early follicular phase at baseline and 12 weeks.


There was a moderate decrease in serum-free estradiol and estrone levels in the experimental group, according to the report in the February 15th issue of Cancer. There were increases of serum hormone-binding globulin levels in 41.4% and 37.5% of the experimental and placebo groups, respectively.


The team notes that 53.85% and 37.5% of the experimental and placebo groups, respectively, had decreases of free estradiol. Decreases in estrone were observed in 55.56% and 42.86% of the subjects, respectively.


"Those participants in the experimental group who consumed soy had their mean menstrual cycle length increased by 3.52 days compared with a mean decrease of 0.06 days in the placebo group (p = 0.04) from baseline to the third menstrual cycle," Dr. Kumar and colleagues explain.


The mean follicular phase increased by 1.46 days in the experimental group, compared with 0.14 days for the placebo group (p = 0.08), they add.


"An increase in menstrual cycle length would reduce the number of menstrual cycles during a lifetime, thereby reducing the total number of times the breast is exposed to estrogen," Dr. Kumar's group points out. Furthermore, "women will spend more days in the increased follicular cycle, when proliferation is at its lowest."


"These effects are mediated by the pituitary gland," they continued, "and long-term effects on the pituitary gland may result in an overall antiestrogenic effect and, thus, in a lower risk for breast carcinoma."

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