Black cohosh, an herb increasingly used by women as an alternative to estrogen replacement therapy, may reduce hot flashes by targeting serotonin receptors, according to a team of researchers from the University of Illinois at Chicago. The finding, the first to show a likely mechanism of action for the herb other than estrogen, increases the likelihood that the herb is safe to use, they say. Until now, many scientists thought that black cohosh worked by targeting receptors for estrogen, the same hormone used in commercial hormone replacement medicine that has recently been associated with adverse side effects, including breast cancer and stroke.

“This study shows that black cohosh does not appear to be estrogenic whatsoever and, as a result, is less likely to pose some of the dangers associated with traditional estrogen replacement therapy,” says study leader Judy L. Bolton, PhD, a professor at the university’s College of Pharmacy.

The researchers found that black cohosh had no estrogenic effects on a specially selected group of rats. In related lab studies, they also found that the extract is capable of binding to human serotonin receptors, including those that help regulate body temperature. Antidepressant medications, which some people believe may help reduce hot flashes, also bind to the same receptors.

Researchers still do not know the specific chemical or chemicals in black cohosh that target the serotonin receptors. Nor do they know if the herb may target hot flashes via additional mechanisms. Further studies are underway to find answers to these questions, they say.

American Chemical Society, Sep 7, 2003