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, while some herbal supplements,
such as red clover, 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 told a meeting of the American Association for Cancer
Research.
She said a woman who did not know she had cancer could be endangered by
taking the supplement.
"This stresses that we really need more research into herbal therapies and
natural therapies."
Davis and colleagues in her lab and in Canada fed black cohosh to female mice
bred so that they are prone to breast cancer. They gave them the daily equivalent of 40 mg 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 percent of mice that ate black cohosh had the cancer
spread to the lung, compared to 11 percent 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 who have 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.
