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More Evidence That Plant Estrogens Don't Reduce Hot Flashes

Two isoflavone-containing dietary supplements were no more effective than placebo in decreasing hot-flash counts.

In the wake of findings from the Women's Health Initiative (Journal Watch Women's Health Aug 7 2002 ), the literature is teeming with studies designed to evaluate alternatives to hormone therapy for treating hot flashes (Journal Watch Women's Health Aug 6 2003, Aug 6 2003, and May 7 2003). Isoflavones, polyphenol compounds that are structurally similar to estrogen, have been shown to bind to estrogen receptors; those derived from soy or red clover are marketed widely to treat menopausal symptoms. In this randomized, double-blind, manufacturer-supported trial, researchers evaluated the efficacy of 2 over-the-counter, red-clover-derived dietary supplements in treating hot flashes.

A total of 252 postmenopausal women who were experiencing at least 35 hot flashes per week were assigned to receive Promensil (82 mg isoflavones/day), Rimostil (57 mg isoflavones/day), or placebo. At 12 weeks, the reductions in mean hot-flash count did not differ significantly among the 3 groups. The Promensil group showed a significantly faster reduction in hot-flash count than did the placebo group.

Comment: Although well-designed, this study has limitations. All of the women were postmenopausal, so applicability of the findings to perimenopausal women is unknown. In addition, the study group was predominantly white and highly educated. Further, there is evidence that, given the short half-life of isoflavones (6-10 hours), dosing several times daily might be more beneficial than the once-daily dosing used here. The faster reduction in hot-flash count in the Promensil group does support a biologic effect of the product. However, the supplements at these dosages were not efficacious in these postmenopausal women. Our patients need to understand that heavy marketing of a supplement is not necessarily based on conclusive scientific evidence that the product actually works.

— Ann J. Davis, MD

Published in Journal Watch Women's Health September 4, 2003

Citation(s):

Tice JA et al. Phytoestrogen supplements for the treatment of hot flashes: The Isoflavone Clover Extract (ICE) study: A randomized controlled trial. JAMA 2003 Jul 9; 290:207-14.

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