Black cohosh is an herbaceous plant whose roots are purported to have anti-inflammatory and pain-relieving effects. Supplements containing black cohosh are often marketed for treatment of the symptoms of menopause. Some reports of liver toxicity have been reported with the use of supplements containing black cohosh; however, a review in the February 2008 issue of "Evidence-Based Complementary and Alternative Medicine" reports that in clinical trials with over 3,800 participants no adverse liver effects were reported. Black cohosh supplements should be taken under the advice of a physician; they may be contraindicated for some people who have pre-existing liver conditions.
Menopause Symptoms
Black cohosh supplements may alleviate menopausal symptoms, including hot flashes, sweating, sleep disturbances and depression. The National Center for Complementary and Alternative Medicine (NCCAM) reports that clinical studies have shown inconsistent results on the effectiveness of black cohosh for treating menopausal symptoms. A study funded by NCCAM did not find that black cohosh was effective in relieving hot flashes or night sweats, but NCCAM is currently funding a longer-term study to better evaluate the effectiveness of black cohosh supplements. Results from this study have not yet been made available. An analysis of seven clinical trials published in the January-February 2010 issue of "Alternative Therapies in Health and Medicine" concludes that supplements containing black cohosh improved menopausal symptoms overall by 26 percent, but there was significant variations in the results of these trials.
Dosage and Metabolism
An article in "Alternative Medicine Review" notes that the active chemicals in black cohosh are triterpene saponins and that the plant does not contain estrogenic substances. This source reports that in clinical trials black cohosh supplements were most commonly administered in doses ranging between 40 and 80 mg per day, which is equivalent to 2 to 4 mg of triterpene saponins. The Office of Dietary Supplements (ODS) reports that standardized commercially marketed black cohosh supplements contain 1 mg of total triterpene saponins, expressed as 26-deoxyactein in each 20 mg dose.The liver metabolizes triterpene saponins and other chemicals in black cohosh, and there is some concern that toxic metabolites may be produced; however the article in "Evidence-Based Complementary and Alternative Medicine" notes that in women administered doses up to 128 mg of black cohosh, liver metabolism did not produce any known toxic compounds that could be detected in the urine.
Possible Liver Toxicity
A review in the March 2010 issue of "Menopause" notes that 11 published case reports of liver toxicity and 58 reports of liver toxicity in national registries have been attributed to black cohosh supplements. The review in "Evidence-Based Complementary and Alternative Medicine" reports that some animal studies have demonstrated liver toxicity for black cohosh at doses exceeding 100 mg per kg, which approximates a dose of more than 5 g per day in a 50 kg woman.
Negative Studies
The authors of the review in "Menopause" conclude that because of poor case report quality, uncertainty of black cohosh product use and the lack of reporting of confounding variables such as alcohol and other medication use, the data do not support that black cohosh supplements are the cause of liver toxicity. The study in "Evidence-Based Complementary and Alternative Medicine" reports that at doses of dose of 500 to 1000 mg daily administered for the treatment of menopause symptoms black cohosh did not adversely affect markers of liver toxicity in 107 women. In this study, the black cohosh supplement contained 2.5 percent triterpenes, equivalent to between 12.5 and 25 mg, which is much greater than the more commonly used doses.
Other Adverse Effects
The ODS reports that in clinical trials black cohosh supplements cause few adverse effects. The noted effects were headaches, gastrointestinal upset and weight problems.
References
- "Alternative Medicine Review"; Cimicifuga racemosa; 2003
- Office of Dietary Supplements: Black Cohosh
- PubMed: Efficacy of Black Cohosh-Containing Preparations on Menopausal Symptoms: A Meta-Analysis
- The National Center for Complementary and Alternative Medicine: Black Cohosh
- PubMed: Black Cohosh and Suspected Hepatotoxicity: Inconsistencies, Confounding Variables, and Prospective Use of a Diagnostic Causality Algorithm. A Critical Review
- "Evidence-Based Complementary and Alternative Medicine"; Black Cohosh Hepatic Safety: Follow-up of 107 Patients Consuming a Special Cimicifuga racemosa rhizome Herbal Extract and Review of Literature; Fabio Firenzuoli et al.; February 2008
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