Black Cohosh: Good News and Bad News

May 3, 2005


Subject: Extracts of Black Cohosh can change the cytotoxicity of chemotherapy.


Black Cohosh or to use the scientific name, Cimicifuga racemosa , is a popular herb for relieving menopausal symptoms, especially hot flashes. Women undergoing chemotherapy for breast cancer are often thrown into menopause as a side effect of treatment. When they go into menopause suddenly the symptoms experienced can be very pronounced and they are desperate for relief. Cimicifuga is generally considered safe to use with breast cancer and many of these women end up taking it. A new study just published in Breast Cancer Research [i] should make us pause and reconsider this option.


The researchers, working at the Cancer Center at Yale University , examined the effect of Cimicifuga extracts on cancer cells in combination with various chemotherapy drugs. Results varied. With some drugs the combination increased the effectiveness of the drug, with other drugs, effectiveness decreased. No change was seen with radiation treatments.


The Cimicifuga extracts increased the cytotoxicity of Doxorubicin (Adriamycin) and Docetaxel (Taxotere) but decreased the cytotoxicity of Cisplatin or 4-HC (an analog of cyclophosphamide).



The effect of the Cimicifuga with Doxorubicin was not mild. In measurements of surviving fractions of breast cancer cells incubated with Doxorubicin adding the Cimicifuga decreased the surviving faction from 1 in 100 to 1 in 10,000 or from 10 -2 to 10 -4 . That's a hundred-fold increase in the effectiveness of doxorubicin!


Interestingly the researchers did not leap for joy with excitement as they reported these findings. They acknowledged that increasing the cytotoxic effect is attractive but they expressed concern that the combination might increase the undesirable side effects on the bone marrow. We aren't as worried as they are.


With other herb/drug combinations that increase cancer cell death, the increased effect has been on the cancer cells and not on healthy cells. Women have been using Cimicifuga during chemotherapy for years. If the toxic effect on bone marrow was of similar hundred-fold magnitude as the cytotoxic effect on cancer cells, someone would probably have noticed by now.


The researchers also compared several different brands of Cimicifuga extract. As expected the “better” companies had more striking action. Gaia had the most effect while Nature's Answer the least action.


Although Cisplatin action and Docetaxel action were inhibited by Cimicifuga , the inhibition was relatively small in comparison to the combined action with Doxorubicin. Rather than powers of ten the changes are expressed in tenths of a power. Let me try and write this in scientific notation. For example at 30 microM of Cisplatin, the surviving fraction increased from about 10 -1..9 to 10 -1.8 when Cimicifuga was added to the experiment. Although this is a statistically significant difference, it may or may not be clinically significant.


Of course all these experiments were done on cells in test tubes. Will the same effect be seen in living animals? The implications of these early findings are important; we can expect to see animal studies in the near future.



[i] Breast Cancer Research and Treatment. Alteration of the effects of cancer therapy agents on breast cancer cells by the herbal medicine black cohosh. Sara Rockwewll, Yanfeng Liu, Susan Higgins. (2005) 90:233-239

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