Many menopausal women who are afraid that hormone replacement therapy could increase their risk of breast cancer have turned to the herbal supplement black cohosh an alternative in recent years.
But a large, NIH-sponsored, carefully controlled study published in the Annals of Internal Medicine Monday reports that, unlike HRT, the supplement doesn't work to help hot flashes or other menopausal symptoms.
The study measured the effect of three different combinations of black cohosh, an extract from the roots of a plant native to North America. Lead researcher Katherine Newton, of the Group Health Center for Health Studies in Seattle, says women in the study were randomly broken down into several groups. Some received one of the black cohosh blends; others took a placebo. None of them knew if they were getting the real thing or not.
At the end of the study, Newton says, "There was no difference between the herbal supplements and placebo in relieving hot flashes in women at any of our study points. And we looked at 3, 6 and 12 months."
Newton says she went into the study with a very open mind. The prior research on black cohosh was inconclusive. So she didn't know what she'd find.
"I wouldn't say it was either a surprise or not a surprise," Newton says, "but it was disappointing.... It would have been nice to find a therapy other than hormone therapy to help women through the menopause transition."
Doctors who specialize in treating the symptoms of menopause say they're increasingly left with an empty bag of tricks. Hormone therapy may be safe only at low doses for short periods of time. And anti-depressants, while effective, often bring side effects.
Gynecologist Gail Greendale of UCLA says she is convinced by the new study published today. But she points out that the study also found that women in both the placebo and black cohosh groups experienced mild relief — up to two fewer hot flashes per day. Perhaps the relief is simply a product of expectation, she says.
"It points up an existential question in medicine," Greendale says, "which is: If something works by a placebo effect, should we just smile and say that's good — and not complain too much?" Greendale says that in the case of black cohosh, it's a tricky call.
Although total sales of the supplement run into the tens of millions of dollars every year, there have never been any long-term studies to determine whether its safe.