Approximately 70% of all women experience hot flashes and/or night sweats (also called vasomotor symptoms or VMS) during the menopause transition.  Although estrogen-containing hormone therapy is highly effective in managing these symptoms, various studies have raised concerns regarding the risks associated with prolonged use of hormone therapy and many women now use other non-hormonal options to manage their symptoms, including over-the-counter complementary and alternative medicines (CAMs), including soy isoflavones, black cohosh, and omega-3 fatty acids.  However, the data regarding the effectiveness of these alternative treatments has been mixed.

Soy-based products have long been touted as a treatment for menopausal symptoms.  However, many of the clinical studies measuring the effectiveness of dietary sources of soy isoflavones (e.g., soy beverages, soy powder) for the treatment of menopausal vasomotor symptoms (i.e., hot flushes, night sweats) have been negative.  It must be noted, however, that in many of the trials, hot flashes improved in both placebo and treatment groups, indicating high placebo response rates in these studies.  Thus, it is difficult to distinguish between the beneficial effects of soy, placebo response, and non-specific effects of monitoring and study participation.

S-equol has recently received attention for its ability to alleviate VMS in menopausal women. S-equol is found in only trace amounts in very few foods; S-equol is produced in the body as an intestinal bacterial metabolite of the soy isoflavone, daidzein.  Not everybody can produce S-equol: only about 50% of Asians and 25% of non-Asians host the intestinal bacteria that convert daidzein into S-equol.  What has excited researchers about S-equol is that some studies indicate equol producers are more likely to benefit from soy consumption than non-producers with respect to both cardiovascular disease and osteoporosis.

Clinical trials evaluating the effectiveness of an S-equol have demonstrated improvement in VMS; however, these trials were small in size and primarily included Japanese women for whom hot flashes are less bothersome. The only randomized controlled trial carried out in the United States found that S-equol significantly reversed the severity and frequency of hot flashes, but the study lacked a placebo group, although it did include an active control.

The daily dose of S-equol used in most trials has been 10?mg; however, it appears that women receiving higher dosages of S-equol (40 mg in one study, up to 200 mg in another) experience greater benefit.  Because its half-life is 7–10 hours, it is typically given twice daily. The safety data for S-equol is limited but do not suggest cause for concern, especially with regard to its effects on breast and endometrial tissue.  S-equol is thought to have estrogenic activity; thus, its use is typically avoided in women with a personal of family history of breast cancer.

Further studies are essential before we can draw definitive conclusions regarding the effectiveness of S-equol for the management of VMS, but the preliminary studies are promising and suggest the S-equol is well-tolerated by most women.

Ruta Nonacs, MD PhD

Crawford SL, Jackson EA, Churchill L, Lampe JW, Leung K, Ockene JK.  Impact of dose, frequency of administration, and equol production on efficacy of isoflavones for menopausal hot flashes: a pilot randomized trial.  Menopause. 2013 Sep;20(9):936-45.

Jenks BH, Iwashita S, Nakagawa Y, Ragland K, Lee J, Carson WH, Ueno T, Uchiyama S.  A pilot study on the effects of S-equol compared to soy isoflavones on menopausal hot flash frequency.  J Womens Health (Larchmt). 2012 Jun;21(6):674-82. doi: 10.1089/jwh.2011.3153.

Utian WH, Jones M, Setchell KD.  S-equol: A Potential Nonhormonal Agent for Menopause-Related Symptom Relief.  J Womens Health (Larchmt). 2015 Mar;24(3):200-8.