Posted by Chantel M. Contributed by US National Library of Medicine National Institutes of Health
In the study of "Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis" by Hooper L, Ryder JJ, Kurzer MS, Lampe JW, Messina MJ, Phipps WR, Cassidy A., posted in US National Library of Medicine National Institutes of Health, found that In premenopausal women, meta-analysis suggested that soy or isoflavone consumption did not affect primary outcomes estradiol, estrone or SHBG concentrations, but significantly reduced secondary outcomes FSH and LH [by approximately 20% using standardized mean difference (SMD), P = 0.01 and 0.05, respectively]. Menstrual cycle length was increased by 1.05 days (95% CI 0.13, 1.97, 10 studies). In post-menopausal women, there were no statistically significant effects on estradiol, estrone, SHBG, FSH or LH, although there was a small statistically non-significant increase in total estradiol with soy or isoflavones ( approximately 14%, SMD, P = 0.07, 21 studies). CONCLUSIONS Isoflavone-rich soy products decrease FSH and LH in premenopausal women and may increase estradiol in post-menopausal women.