In a study, women who took black cohosh to reduce their menopausal symptoms were about 60% less likely to develop breast cancer than women who didn't take black cohosh. Does this mean black cohosh lowers breast cancer risk? Maybe. But this study all by itself DOESN'T answer that question.
This small study does show that taking black cohosh was ASSOCIATED with a decrease in breast cancer risk. This isn't the same thing as concluding that black cohosh caused the decrease in risk. As the researchers point out, much more research needs to be done to prove conclusively that black cohosh lowers breast cancer risk.
Black cohosh seems to help decrease menopausal symptoms because it contains phytoestrogens, substances that act a lot like estrogen. When you go through menopause, your estrogen levels drop significantly. This is why many women experience hot flashes. Herbal remedies such as black cohosh that contain phytoestrogens are thought to help because the phytoestrogens take the place of the missing estrogen. Phytoestrogens also can have anti-estrogen effects. Since estrogens can cause hormone-receptor-positive breast cancer to develop and grow, it's possible that the anti-estrogen effects of black cohosh explain the reduced risk in the women who used it.
Very little research has been done on the effectiveness and safety of black cohosh or other supplements to treat hot flashes. Until doctors know more, we can't recommend black cohosh to lower breast cancer risk. If you're considering taking black cohosh or any other herbal supplement for menopausal symptoms, talk to your doctor before taking the supplement. Some dietary supplements can interfere with breast cancer treatment and prescription medications. To learn more about supplements, visit the breastcancer.org Nutrition Section. To learn more about risk reduction, visit the breastcancer.org Lower Your Risk Section.