Several studies have documented the efficacy of the supplement containing S-equol to reduce the incidence and frequency of menopausal symptoms, particularly hot flashes and neck and shoulder muscle stiffness. These include clinical trials in both Japanese and U.S. post menopausal women. Here are details.

  1. Japanese postmenopausal women, all of whom were S-equol non-producers, significantly improved several of their menopausal symptoms after 12 weeks of daily 10 mg doses (5 mg BID) of S-equol via a supplement. In this randomized, double-blind, placebo-controlled study, the 66 women taking the supplement reduced their frequency of hot flashes by 58.7 percent, significantly more than the 34.5 percent reduction experienced in the 60 women receiving a placebo (P=0.009). The women were prescreened for S-equol production and were non-producers of equol and they were screened prior to the study for placebo response. Of the 34 women who enrolled with at least three hot flashes daily, the women receiving S-equol had a 62.8 percent reduction in their daily hot flash frequency, significantly greater than 23.6 percent reduction experienced by the 28 women in the placebo group (P=0.009). Women receiving the supplement also had significant decreases in the severity of their hot flashes (P=0.012), as measured by the Climacteric Symptom Evaluation Form Checklist, which measured the severity of 22 menopausal symptoms as well as the hot flash frequency. The women receiving S-equol had significant improvements in the severity of their neck or shoulder muscle stiffness scores compared to those in the placebo group (P=0.004). Of note, women in Japan in general experience fewer hot flashes but experience more neck and shoulder stiffness than women in the United States. Six weeks after the treatment ended, the investigators observed the return of both the women's hot flashes and their neck or shoulder stiffness. No adverse events were reported in this study and the supplement was well tolerated.1
  2. Daily 10 mg doses of S-equol via a supplement improved menopausal symptoms, especially shoulder stiffness after six weeks of treatment, compared with the placebo group (P=0.034), in this double-blind, placebo-controlled study examining 105 women who took the supplements for 12 weeks. Also, measurements of the thickness of their uterine endometrial lining and analysis of their vaginal epithelium revealed no biological effects of the supplement on their reproductive organs. All of the women in this study were S-equol nonproducers.16
  3. Supplements containing S-equol had positive effects on menopausal symptoms and mood states in a randomized, double-blind, placebo-controlled study involving 127 healthy pre-, peri- and post-menopausal Japanese women. At the study start, women who were equol producers had significantly fewer total menopausal symptoms and anxiety scores than nonproducers. When compared with their measures at the study start, peri- and post-menopausal women who were nonproducers but who received daily 30 mg doses of S-equol showed significant decreases in psychological (P‹0.01), anxiety (P‹0.01), somatic (P‹0.05), vasomotor (P‹0.05) and total menopausal (P‹0.01) scores in Green Climacteric Scale. However, when compared with nonproducers who received a placebo, this group of women showed significantly lower somatic scores (P‹0.05), as well as significantly lower scores on measures of anxiety (P‹0.05), of dejection (P‹0.05) and of fatigue (P‹0.01) and increases in scores of vigor (P‹0.05). No adverse effects were reported in the study, except for a systemic rash in one woman.5
  4. Daily doses of 10, 20 or 40 mg of S-equol via supplements for eight weeks in 102 healthy postmenopausal U.S. women reduced the frequency of their moderate to severe hot flashes, as did 50 mg doses of a soy isoflavone supplement, used as a comparator in this double-blinded study. Women were prescreened for placebo response. More women in the 10, 20 and 40 mg S-equol groups achieved a 50 percent or more reduction in their average daily hot flash frequency than in the isoflavone group: respectively, 25.0, 27.3, 42.9 (P=0.056) and 16.0 percent. The 20 mg S-equol dose neared statistical superiority (P=0.076), the 10 mg dose was similar (P=0.503) and the 40 mg dose was significantly more effective than the soy isoflavones in reducing hot flash frequency (P=0.021). After stratifying by baseline frequency of hot flashes (≤8 or ›8/day), a comparison of treatment effects on mean daily hot flash frequency as determined over an entire 8-week treatment period showed superiority in subjects with >8/day hot flashes at baseline. For this subgroup, the difference in reduction of daily hot flash frequency compared to isoflavone treatment of the 20 mg and 40 mg S-equol dosages was demonstrated (P=0.045 and P=0.001, respectively). The effect of 10 mg S-equol approached superiority at P=0.063. Muscle and joint pain score reduced significantly in the 10 and 20 mg S-equol groups compared to those in the isoflavone group (P‹0.05). Investigators used the validated Greene Climacteric Scale. No trends or clinically meaningful changes were identified in the women's laboratory blood or urine tests, hormone levels, electrocardiographs, physical examinations or vital signs. The trial documented treatment-emergent adverse effects in participants of all the treatment groups. Such effects occurring in more than 5 percent of each group included abdominal distention, constipation and endometrial hypertrophy, the thickening of the lining of the uterus. The endometrial hypertrophy was identified by transvaginal ultrasounds and assessed by the study's medical monitor, and any changes observed were not considered to be clinically significant.17