A Pilot Study on the Effects of S-Equol Compared to Soy Isoflavones on Menopausal Hot Flash Frequency

Background: S-equol, a metabolite of the soy isoflavone daidzein, has been proposed as having potential for relief of menopausal symptoms. This study compared the efficacy of the natural S-equol supplement, SE5-OH, with isoflavones for relieving hot flashes and other menopausal symptoms. Methods: An 8-week randomized, double-blind, active comparator trial with SE5-OH was conducted in postmenopausal women (aged 45-65 years), who experienced 5 hot flashes/day. Participants (n = 102) were assigned to one of four treatment groups: 10 (n = 24), 20 (n = 27), or 40 (n = 25) mg S-equol/day or soy isoflavones (n = 26). Participants recorded their hot flash frequency and rated their menopause symptom severity. Results: Reductions in hot flash frequency at week 8 were similar for all treatment groups. However, based on analyses of the cumulative effect for the 8-week period, 40mg/day S-equol had a greater reduction of hot flash frequency compared to isoflavones (p = 0.021). A subgroup analysis further indicated that for subjects with > 8 hot flashes/day at baseline, 20 and 40 mg/day S-equol were superior to isoflavones in reducing hot flash frequency (p = 0.045 and p = 0.001, respectively). In addition, 10 and 20mg/day S-equol improved muscle and joint pain score compared with isoflavones (p = 0.003 and p = 0.005, respectively). Conclusions: S-equol, 10mg/day, appears to be as effective as soy isoflavones at reducing hot flash frequency and more effective for relieving muscle and joint pain in postmenopausal women. S-equol, 20mg/day, alleviates hot flashes to a greater extent than soy isoflavones in those women who experience > 8 hot flashes/day.