The tide of bad news swamping hormone replacement therapy has led more and more women to seek alternative treatments for hot flashes, night sweats, and other woes of menopause. But new research calls into question the safety of one of the most promising options: Black cohosh.

In mice with breast cancer, a daily dose of the herb seemed to promote the spread of the disease, according to a study by Vicki Davis of Duquesne University in Pittsburgh. The news is especially troublesome because black cohosh appeared to be the one safe bet for women with breast cancer. Unlike red clover and soy, it doesn’t contain phytoestrogens, substances that mimic estrogen and are linked with certain cancers.

Does this mean all women should steer clear of black cohosh? Many experts say no. Stacie Geller, a researcher at the University of Illinois at Chicago who is studying the herb, points out that black cohosh was only linked to the spread of tumors in mice that already had breast cancer. Healthy mice were not more likely to develop the disease. “It doesn’t give me pause to continue to recommend it for most women,” she says. What’s more, an extensive review published in the journal Menopause concluded that the herb is safe for menopausal women.

The review was written before the mouse study was made public. But physician and author Tieraona Low Dog of Integrative Medicine Associates in Corrales, N.M., says that while the results of the mouse study warrant concern and further research, she stands by the overall safety of black cohosh for women who have neither breast cancer nor a history of the disease. Since women in the early stages of the disease may be unaware they have it, though, any woman who takes black cohosh should be sure to get regular checkups.

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