Most women experience hot flashes or night sweats during their menopause and perimenopause. Hot flashes can disturb sleep, resulting impaired concentration and other physical problems. Hormone treatment is often recommended to reduce hot flashes but can have side effects, such as increased breast cancer risk. As a result, many women are looking for alternative therapies, such as treatment with isoflavones. Previous studies have already observed that Asian women who consume more soyfoods than American women experience less hot flashes, suggesting that isoflavones may play a role in controlling hot flashes. Dr Taku and co-workers of the National Institute of Health in Tokyo conducted a review study of 17 randomized controlled trials on the effects of soybean isoflavones on the frequency and severity of hot flashes.
The meta-analysis showed that daily intake of about 54 mg soy isoflavones for 6 weeks to 1 year reduced the frequency of hot flashes by 20% and also reduced the severity of hot flashes by 26%. The researchers also found that isoflavones supplements containing more than 18.8 mg genistein were twice as affective in reducing the frequency of hot flashes that lower levels of genistein. Trials with intervention durations of more than 12 weeks showed threefold greater reduction in the frequency of hot flashes. The exact mechanism by which soy isoflavones reduce hot flashes has not been established but researchers speculate that it is related to the structural similarity of isoflavones and human estrogen. The study concluded that soy isoflavones supplements are significantly more effective that placebo in reducing the severity and frequency of hot flashes.
Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause. 2012 Mar 19.