Soy protein and isoflavone effects on vasomotor symptoms in peri- and postmenopausal women: the Soy Estrogen Alternative Study

Objective: To investigate the efficacy of dietary soy proteins containing differing amounts of isoflavones on the number and severity of vasomotor symptoms (hot flashes and night sweats) in peri- and postmenopausal women. Design: A double-masked, randomized, controlled, clinical trial was conducted. A total of 241 community-dwelling women reporting vasomotor symptoms at baseline were randomized into one of three groups. In all groups, participants consumed a daily supplement containing 25 g of soy protein and were randomly assigned to one of three groups: (a) isoflavone extracted soy protein (control), (b) soy protein with a medium dose of isoflavones (42 mg/day), or (c) soy protein with a higher dose of isoflavones (58 mg/day). The primary outcome measure in this trial was change in reported vasomotor symptoms. Results: A reduction in the number and severity of vasomotor symptoms was observed in all three treatment groups. No significant differences in the number and severity of vasomotor symptoms were observed among the high isoflavone, middle isoflavone, or control groups. The lack of a between-treatment group effect was observed even after stratified by number of baseline symptoms and use of traditional hormone replacement therapy. Conclusions: These data suggest that soy protein containing 42 or 58 mg of isoflavones is no more effective than isoflavone-extracted soy protein for improving the number and severity of vasomotor symptoms in peri- and postmenopausal women.