S-equol: a potential nonhormonal agent for menopause-related symptom relief

Many women suffering from vasomotor symptoms (VMS) are now seeking nonpharmaceutical treatments for symptom relief. Recently, S-equol, an intestinal bacterial metabolite of the soybean isoflavone daidzein has received attention for its ability to alleviate VMS and provide other important health benefits to menopausal women. S-equol is found in very few foods and only in traces. About 50% of Asians and 25% of non-Asians host the intestinal bacteria that convert daidzein into S-equol. Clinical trials that evaluated the efficacy of an S-equol-containing product found that VMS were alleviated but these trials were limited in scope and primarily involved Japanese women for whom hot flashes are a minor complaint. The only trial in the United States evaluating hot flashes found symptoms were significantly reduced by S-equol, but the study lacked a placebo group, although it did include a positive control. The daily dose of S-equol used in most trials was 10 mg, and because the half-life of S-equol is 7-10 hours, to maximize efficacy, it was taken twice daily. Subanalysis of epidemiologic studies suggests that equol producers are more likely to benefit from soyfood consumption than nonproducers with respect to both cardiovascular disease and osteoporosis, although the data are inconsistent. The limited safety data for S-equol do not suggest cause for concern, especially with regard to its effects on breast and endometrial tissue. Further studies are needed before definitive conclusions of its effectiveness for VMS can be made, but the preliminary evidence warrants clinicians discussing the potential of S-equol for the alleviation of VMS with patients.