The risk-benefit ratio of isoflavone preparations in menopausal women is currently under examination. The heterogeneity in the design and outcome of the published clinical trials has been addressed. We identified and analyzed eight clinical placebo-controlled double-blind trials with a minimum duration of 12 weeks, from which the daily frequency of hot flushes and their standard deviation before and after the trial could be derived. The data was submitted to a metaanalysis. Difference between verum- and placebo-treated groups was found statistically significant (p <0.0001), and the overall outcome (medium and 95% CI) clearly favoured verum.
On the risk side the extrapolation of findings from pure estrogen receptor alpha models must be questioned, as the results do not sufficiently reflect the situation in the human body. Likewise, the few clinical results which may be interpreted as giving hints to potential carcinogenic risks stand in contrast with the broad experience from toxicological and safety trials. Safety of isoflavone preparations has been clinically confirmed with daily doses up to 900 mg of isoflavones and a duration of supplementation of up to three years.
In conclusion, women with menopausal vasomotor symptoms may profit from supplementation, either with soy preparations alone or in combination with hormones.
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