Black Cohosh Side Effects and Warnings

Safety Issues

Black cohosh seldom produces any side effects other than occasional mild gastrointestinal distress. One rigorous study looked for possible deleterious effects on cholesterol levels, blood sugar, and blood coagulability, and did not find any.

Studies in rats have found no significant toxicity when black cohosh was given at 90 times the therapeutic dosage for a period of 6 months. Since 6 months in a rat corresponds to decades in a human, this study appears to make a strong statement about the long-term safety of black cohosh.

Unlike estrogen, black cohosh does not stimulate breast cancer cells growing in a test tube. However, black cohosh has not yet been subjected to large-scale studies similar to those conducted for estrogen. For this reason, safety for those with previous breast cancer is not known. Also, because of potential hormonal activity, black cohosh is not recommended for adolescents or pregnant or nursing women.

There are a growing number of case reports in which it appeared that use of a black cohosh led to severe liver injury. However, it is not clear whether the cause was black cohosh itself, or a contaminant present in the product.

One highly preliminary study found that black cohosh might reduce the effectiveness of the chemotherapy drug cisplatin.

Safety in young children or those with severe liver or kidney disease is not known.

Black cohosh should not be confused with blue cohosh (Caulophyllum thalictroides), which has different properties, treatment uses, and side effects. Black cohosh is sometimes used with blue cohosh to stimulate labor, but this therapy has caused adverse effects in newborns, which appear to be due to blue cohosh.

Interactions You Should Know About

Black cohosh might reduce the effectiveness of cisplatin.

6. http://nccam.nih.gov/health/blackcohosh/ataglance.htm, accessed 11/16/11