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.
(See also Overview of Dietary Supplements.)
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 menopausal 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 2016 review of botanical products that included black cohosh also found no benefit for menopausal symptoms (2). A 2017 network meta-analysis in women with an intact uterus found that, compared to placebo, black cohosh decreased vasomotor menopausal symptoms. However, black cohosh was not as effective as hormonal treatments (3). 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 gastrointestinal 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 (4) 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 (5).
Leach MJ, Moore V: Black cohosh (Cimicifuga spp.) for menopausal symptoms. Cochrane Database Syst Rev9:CD007244, 2012. doi: 10.1002/14651858.CD007244.pub2
Franco OH, Chowdhury R, et al: Use of plant-based therapies and menopausal symptoms: a systematic review and meta-analysis. JAMA 315(23):2554-63, 2016. doi: 10.1001/jama.2016.8012
Sarri G, Pedder H, Dias S, et al: Vasomotor symptoms resulting from natural menopause: a systematic review and network meta-analysis of treatment effects from the National Institute for Health and Care Excellence guideline on menopause. BJOG 124(10):1514-1523, 2017. doi: 10.1111/1471-0528.14619
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. doi: 10.1111/jphp.12055
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institutes of Health (NIH), National Center for Complementary and Integrative Health: General information on the use of black cohosh as a dietary supplement