The Pharmaceutical Journal
Vol 271 No 7258 p76
19 July 2003

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Isoflavone supplements no better than placebo for reducing hot flushes

Women who take phytoestrogen supplements to combat menopausal symptoms may not gain any more benefit than if they took placebo, new data indicate.

American researchers tested the effects of two supplements (containing 82mg and 57mg of total isoflavones extracted from red clover) and placebo in 252 postmenopausal women who were experiencing at least 35 hot flushes per week.

They found that reductions in daily hot flushes were similar for all three groups (34 to 41 per cent over 12 weeks) and, on average, women were still experiencing more than five hot flushes per day at the end of the study. Heavier women appeared to benefit more from the supplements, a finding that surprised the researchers. "Postmenopausal women with higher body mass indexes tend to have higher circulating oestrogens due to conversion of androgens to oestrogens by aromatase in adipocytes," they explain.

Hot flushes were reduced most rapidly in women taking the supplement containing a higher level of isoflavones. The researchers suggest this could be down to chance or because the isoflavones contained in the first supplement — biochanin A and genistein — are more effective at reducing hot flushes than formononetin and daidzein — the isoflavones in the second. The study is published in JAMA (2003;290:207).