Aims: To review current research on the effects of soy consumption on menopausal symptoms.
Methods: To review results of recent meta-analyses and individual clinical trials.
Main results: One recent meta-analysis reported that isoflavone supplementation was associated with a 34% reduction in hot flashes, with increased efficacy as the baseline number of flashes and isoflavone dose increased. A second review concluded that consumption of at least 15 mg genistein, rather than total isoflavones, is responsible for the reduction in symptoms. Results of these two reviews are supported by most subsequent randomized controlled trials.
Conclusions: Consumption of 30 mg/day of soy isoflavones (or at least 15 mg genistein) reduces hot flashes by up to 50 %. This total reduction includes that provided by "the placebo effect". The greatest benefit may be realized when the isoflavone-rich food or supplement is taken in divided doses by subjects who experience at least four hot flashes/day.