December 2006

Black cohosh study faulty says ABC

A recently-published clinical trial testing the popular herb black cohosh is inconsistent with the positive outcomes for treating menopause symptoms seen in the majority of published clinical trials, says the American Botanical Council.

“The medical literature contains many controlled and uncontrolled trials that support the efficacy of the two leading black cohosh preparations for treating menopause symptoms,” said Mark Blumenthal, founder and executive director of ABC.

A number of herb experts cautioned that this trial must be seen in context of the entire body of clinical research on black cohosh. According to Mary Hardy, MD, a physician in Los Angeles who has been researching herbal dietary supplements for over a decade, and an expert on black cohosh clinical trials, “This study should not be considered the definitive study on black cohosh. These results should be placed in the context of all of the black cohosh trials—many of which have shown efficacy for other commercially available products.”

Gail Mahady, PhD, an associate professor of pharmacognosy at the University of Illinois, said, “Since 2003 there have been about 10 clinical studies on black cohosh published and all were positive.”

The year-long trial did not show any significant benefit in reducing hot flashes or night sweats for two different black cohosh preparations — one a black cohosh extract and the other black cohosh with other herbs added — a combination of the black cohosh/herbal mixture with an enhanced soy diet. (The authors acknowledged that it was difficult to ensure compliance of the added soy diet for an entire year.)

One group of women in the trial used conventional hormone replacement therapy (HRT) but this treatment was terminated after researchers in another trial on HRT discovered adverse cardiovascular and cancer effects associated with the conventional hormones in 2002.

Called the “Herbal Alternatives for Menopause Trial”(HALT), the study, published in the Annals of Internal Medicine on December 19, was a one-year, randomized, double-blind, placebo-controlled, 5-arm trial.

Daniel Fabricant, PhD, vice-president of Scientific Affairs at the Natural Products Association with a doctorate in pharmacognosy from the University of Illinois, which is also conducting an NCCAM-funded grant on the same black cohosh extract, said in an e-mail to ABC, “The body of clinical evidence on black cohosh preparations spans more than 3,000 subjects and 50 years using the herbal extract for relief from climacteric (menopausal)/vasomotor symptoms. The weight of the evidence from those studies has been overwhelmingly positive.”

Fabricant also noted that a potentially significant flaw in the trial is the lack of data on secondary trial outcomes in this article.

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