(See also Overview of Dietary Supplements.)
Black cohosh is the underground stem of a plant that can be ingested directly in powdered form or extracted into tablet or liquid form. It should be standardized to contain certain triterpenes. Black cohosh contains no phytoestrogens that can account for its purported estrogen-like effects, but it contains small amounts of anti-inflammatory compounds, including salicylic acid.
Black cohosh is said to be useful for menopausal symptoms (eg, hot flushes, mood lability, tachycardia, vaginal dryness), for menstrual symptoms, and for arthralgias in rheumatoid arthritis or osteoarthritis.
Evidence regarding benefit in relieving menstrual symptoms is conflicting (1). There are few reliable data on its effectiveness for other disorders and symptoms.
A recent review included 16 randomized controlled trials of women (n=2027) using oral preparations of black cohosh (average dose 40 mg). There was no significant difference between black cohosh and placebo in the frequency of hot flushes (3 trials; 393 women) or in menopausal symptom scores (4 trials; 357 women) (1). A lack of standardization of the supplement product used between studies indicates that more research is necessary to reach definitive conclusions.
Adverse effects are uncommon. The most likely are headache and GI distress. Dizziness, diaphoresis, and hypotension (if high doses are taken) may occur.
Theoretically, black cohosh is contraindicated in patients with aspirin sensitivity, liver disease, hormone-sensitive cancers (eg, certain kinds of breast cancer), stroke, or high blood pressure. The US Pharmacopeia (USP), based on a few case reports (2), has recommended that black cohosh products be labeled with a warning declaring that they may be hepatotoxic.
There is little clinical evidence that black cohosh interferes with drugs. However, a recent in vitro study suggests that black cohosh may inhibit the biotransformation or effectiveness of tamoxifen and irinotecan, both chemotherapy drugs (3).
Leach MJ, Moore V. Black cohosh (Cimicifuga spp.) for menopausal symptoms. Cochrane Database Syst Rev9:CD007244, 2012.
Lim TY, Considine A, Quaglia A, et al. Subacute liver failure secondary to black cohosh leading to liver transplantation. BMJ Case Rep, Published online: 5 July 2013. doi:10.1136/bcr-2013-009325.
Gorman GS, Coward L, Darby A, et al. Effects of herbal supplements on the bioactivation of chemotherapeutic agents. J Pharm Pharmacol 65(7):1014-1025, 2013.