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Effects of a standardized soy extract on hot flushes: a multicenter, double-blind, randomized, placebo-controlled study

Faure, Evelyne Drapier MD1; Chantre, Philippe MD2; Mares, Pierre MD3


Objective To investigate the effect of an oral soy isoflavone extract (Phytosoya) on hot flushes in menopausal women.

Design The study was conducted on outpatients according to a multicenter, randomized, double-blind, placebo-controlled, parallel-group design. A total of 75 patients in natural or surgical menopause suffering from at least seven hot flushes per day were randomized to receive during 4 months either soy isoflavone extract (total of 70 mg genistin and daidzin per day) or placebo.

Results There is evidence to suggest that 16 weeks of treatment with soy extract can help reduce the mean number of hot flushes per 24 hours in menopausal women. Withdrawals during this trial made it difficult to obtain an unbiased estimate of the true treatment effect, but numerous sensitivity analyses lend support to the suggestion that taking soy extract can be beneficial in the treatment of hot flushes. In particular, women taking soy extract had a 38% reduction in the mean number of hot flushes by week 4 and a 51% reduction by week 8. By the end of week 16, patients taking soy extract had a 61% reduction in their daily hot flushes versus a 21% reduction obtained with the placebo. “Responders” (defined as patients whose hot flushes were reduced by at least 50% at the end of treatment period) were 65.8% in the soy extract group and 34.2% in the placebo group (p < 0.005).

Conclusion Soy isoflavone extract may help to reduce the frequency of hot flushes in climacteric women and provides an attractive addition to the choices available for relief of hot flushes.

From the 1Department of Gynecology, Hospital Edouard Herriot, Lyon, France; 2Arkopharma Laboratories, Carros, France; and the 3Department of Gynecology, Hospital Caremeau, Nîmes, France.

Received May 24, 2001; revised and accepted April 1, 2002.

This study was funded by Arkopharma Laboratories.

Address reprint requests to: Philippe Chantre, MD, Arkopharma Laboratories, B.P. 28–F06511 Carros, France. E-mail: pchantre@

© 2002 Lippincott Williams & Wilkins, Inc.