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Black Cohosh Safety
Black Cohosh Safety

Do black cohosh preparations require a warning for possible liver toxicity? Yes, according to some regulators, and no, according to many herb experts. The popular herb used for menopausal symptoms is under increased scrutiny. We reported in our last issue that Australian health authorities issued a required label warning in February. Then agencies in the EU and UK issued label warnings in July. In August, Health Canada released a consumer advisory but did not go so far as to require a label warning. They acknowledged that there is simply inadequate data to prove a causal link between the use of black cohosh and the reported liver toxicity cases, many of which were poorly documented. The identity of the herbal material in most implicated preparations lacked adequate confirmation, a persistent problem with such reports.

In September a lawsuit against two dietary supplement manufacturers, whose products were implicated by a patient who received a liver transplant in Nebraska, was dismissed by the presiding judge who stated that the plaintiff’s case and the testimony of her scientific experts failed to meet the test for adequate scientific merit. This is reasonable, as no published scientific evidence to date shows any confirmed molecular or mechanistic basis for suspecting black cohosh rhizome or its extracts as being hepatotoxic, nor any hint thereof. Human clinical trials in which the levels of liver enzymes have been monitored reveal no basis for suspected hepatotoxicity.

As reported in our last issue, the US National Institutes of Health (NIH) conducted a one-day workshop in November 2004 on the safety of black cohosh, concluding that there was inadequate evidence to suggest a causal link to the reported cases of liver toxicity, but also requiring that all NIH-funded clinical trials begin to monitor liver enzymes (elevated liver enzymes are an indicator of liver dysfunction).

At least two reasons can be offered to explain the appearance >of a potential problem. One is that in any population of humans, there will be unexplainable cases of spontaneous liver toxicity. One study of adults in a Canadian health care system concluded that there are 24 such cases per every 100,000 patients, with the etiology of these cases being unrelated to any detectable organic dysfunction, hepatotoxic drugs, etc.

Another potential explanation is the possibility that the “black cohosh” in some of the implicated products may have been another herb, or possibly a different species of black cohosh. A recently published study analyzed 11 “black cohosh” preparations sold in the United States and found that 3 of the products contained different species of Actaea> (A. cimicifuga, A. dahurica>, and A. yunnanensis>) but not the proper species (A. racemosa>, syn. Cimicifuga racemosa>) required by US industry trade policy and FDA regulation for the name “black cohosh.” Whether these other species of Actaea >might contain some hepatotoxic compounds or not remains unclear at this time.

Nevertheless, the evidence thus far strongly supports the overall safety of properly manufactured herbal preparations containing black cohosh. The world-renowned Professor Norman R. Farnsworth of the University of Illinois at Chicago, a founder and trustee of ABC and the principle investigator of an NIH-funded clinical trial on black cohosh, has said that insufficient scientific and clinical evidence currently exist to confirm the alleged hepatotoxicity of black cohosh, and any regulatory policy suggesting required warnings is premature and “not rational.” Numerous other experts agree.

Nevertheless, some companies have begun to consider adding warnings on black cohosh preparations, not because the currently available evidence warrants such action, but because they are concerned about product liability exposure. Ironically, the presence of such warnings on herb products may reduce consumer usage—an unfortunate development considering that black cohosh is one of the safest and probably the most effective alternative treatments to conventional hormone therapy for menopausal symptoms.