A daily dose of S-equol (13.1 mg), delivered via a fermented soy germ-based nutritional supplement to manage menopause symptoms, showed no impact on reproductive or thyroid hormones or the menstrual cycles of premenopausal women, according to a peer-reviewed study reported in a poster at the Academy of Women's Health 2014 annual meeting in Washington, D.C.
Previous controlled clinical trials documented that daily doses of the supplement containing S-equol, a metabolite of the soy isoflavone daidzein, relieved menopausal symptoms, specifically hot flash frequency and muscle discomfort, in both U.S. and Japanese postmenopausal women.
"These data demonstrate that in premenopausal women, use of this supplement does not impact levels of specific endocrine hormones. Furthermore, the S-equol supplement does not impact menstrual cycles of premenopausal women which helps to confirm and expand what we know about safety of the S-equol supplement from previous studies," said coauthor Belinda H. Jenks, Ph.D., director of scientific affairs and nutrition education at Pharmavite LLC, the makers of Nature Made® vitamins and minerals and a subsidiary of Otsuka Pharmaceutical Co. Ltd., which supported the study.
S-equol has the ability to bind to the same estrogen receptors as naturally occurring estrogen, with a strong affinity to the estrogen receptor beta. On binding to the receptor, S-equol mimics some, but not all, activities of estrogen. Because of these actions at the receptor, it has been proposed that S-equol may alleviate some menopause symptoms caused by diminished estrogen production.
No impact from S-equol supplements on reproductive or thyroid hormone levels and menstrual cycle in premenopausal women
During the treatment period and post-treatment period, each of which was lasted for one menstrual cycle in each subject, a dose of a supplement containing 13.1 milligrams (mg)S-equol daily did not significantly alter the levels of five reproductive and three thyroid hormones from pre-treatment values, which remained within the normal range and did not differ from levels in women receiving a placebo in a study of 35 Japanese women aged 20 to 38 years. Moreover, neither the supplement nor the placebo affected the length of the women's menstrual cycles, which averaged 28.4 to 30.0 days, p=0.430 for the difference between groups and p=0.921 for the differences in the three cycle phase measures.
Specifically, the women receiving the supplement did not differ from the 18 women receiving the placebo in delta changes of the levels of luteinizing hormone (treatment minus pre-treatment: p=0.260 and post-treatment minus pre-treatment: p=0.486), follicle stimulating hormone (p=0.322 and p=0.456), estradiol (p=0.712 and p=0.703), progesterone (p=0.085 and p=0.462) and testosterone (p=0.720 and p=0.764). Additionally, the two groups did not differ in measures for levels of thyroid stimulating hormone (p=0.082 and p=0.111), free T3 (a form of triiodothyronine) (p=0.197 and p=0.416) and free T4 (a form of thyroxine), (p=0.223 and p=0.724).
Investigators took blood samples from each woman during the early follicular phase, about three to five days after onset of the period, the late follicular phase, about 10 to 13 days after onset of the period, and the luteal phase, about seven to 10 days after ovulation. The investigators repeated these blood samples during the course of three sequential cycles. During the first and last cycles, the women did not take any treatment, while during the middle cycle; the women received either the supplement or a placebo based on random assignment to a treatment group. This treatment lasted approximately four weeks, depending on the duration of the women's individual cycles.
Only women who had regular menstrual cycles, 28 to 35 days, were accepted and enrolled and of these, 12 were natural equol producers after soy consumption. All of the women self-checked their ovulation cycles using commercial urine tests.
The complete data will be submitted to a peer-review journal for publication.