Scientists Warn About Herb for Menopause

Black cohosh, an herb popular for relieving the hot flashes and some other unpleasant symptoms of menopause, may make cancer more likely to spread, U.S. and Canadian researchers said Saturday.

The news is yet another blow to women looking for something to safely ease the symptoms of menopause, which range from hot flashes to a higher risk of heart disease and cancer.

Hormone replacement therapy has been found to worsen the risk of heart disease, stroke, some cancers and Alzheimer’s disease, while some herbal supplements have been found to do no good.

Many women had been taking black cohosh because it seemed to ease the hot flashes and, because it was herbal, many presumed it was safe.

Not so, researcher Vicki Davis of the Mylan School of Pharmacy at Duquesne University in Pittsburgh said at a meeting of the American Assn. for Cancer Research. She said a woman who did not know she had cancer could be at risk by taking the supplement.

“This stresses that we really need more research into herbal therapies and natural therapies,” Davis said.

Davis and colleagues in her lab and in Canada fed black cohosh to female mice bred so they are prone to breast cancer. They gave them the daily equivalent of 40 milligrams of the supplement, the amount normally recommended for menopausal symptoms.

The mice were not any more likely to develop breast cancer in the first place. But those that did develop it were more likely to see a deadly spread of the cancer, Davis said.

Her team found that 27% of mice that ate black cohosh had the cancer spread to the lungs, compared with 11% of the mice that did not eat the herb.

The findings do not prove that a woman with undiagnosed breast cancer could be endangered by using black cohosh, but Davis said it would be risky to take it. Women with breast cancer -- or any other form of cancer -- may need to be especially wary, she said.

It is not clear how black cohosh may make cancer more likely to spread, Davis said.

“And one thing we don’t know is whether it might accelerate a tumor that might be likely to metastasize or increase the numbers of tumors that would metastasize. But neither one is good,” she said.