Evidence that soy eases hot flashes inconclusive

Despite supplement makers' claims and popular perceptions, the benefits of soy in fighting hot flashes in women going through menopause remain unproven, according to a new analysis of 19 studies.

Soy contains estrogen-like compounds, and researchers have proposed that the amount of soy a woman consumes may influence her risk of having hot flashes and night sweats during menopause. These symptoms are related to the sharp drop in estrogen levels that occurs as women stop menstruating, making it possible that high consumption of estrogen-like compounds could reduce their severity - or eliminate them.

To investigate, Dr. Rafael Bolaños of San Marcos University in Lima, Peru, and colleagues searched the medical literature for clinical trials lasting at least 12 weeks in which soy products were compared with inactive placebo in menopausal women.

The researchers divided the studies into three groups based on the type of supplement used: concentrate of soy isoflavones, the estrogen-like compounds found in soy (3 studies); soy extract (6 studies), or soy dietary supplement (10 studies).

Within each group, women using soy products showed significant improvement of their hot flashes compared to the women on placebo. The extract seemed to have the strongest effects, while soy isoflavones came in second place, and soy dietary supplements came in last.

But because the various studies were so different from one another in terms of dosages used, outcomes measured, and other factors, the researchers say, firm conclusions can't be drawn from the current analysis.

They call for more studies in which these factors are standardized to better establish whether or not soy is helpful to women with menopausal symptoms.

SOURCE: Menopause, online March 1, 2010.