Herbal group reacts to black cohosh study
offer no benefit for hot flushes was probably too short to measure
any effect, says the herbal science group the American Botanical
Council.
The group said that the double-blind, placebo-controlled clinical trial on 132 women conducted by researchers at the Mayo Clinic in Scottsdale, Arizona, and reported at this weeks' meeting of the American Society of Clinical Oncology in Orlando, Florida had numerous weaknesses.
The trial was only four weeks in length, probably too short to measure any effect from the product tested, since most clinical trials on black cohosh have run for three to six months, said ABC.
In addition, the trial's results have not yet been subjected to the peer-review process required for publication in a journal.
Black cohosh preparations have been approved by the German government as nonprescription medications for treatment of menopausal symptoms and are among the most widely-used natural alternatives to hormone replacement therapy (HRT).
However the new study suggested that the herbal was no more effective than a placebo.
ABC says there may also have been problems with the product tested. According to its correspondance with the researchers, they attempted to produce a replica of Remifemin, the market-leading black cohosh product with the most clinical research, which had shown positive results in a pilot trial.
They were unable to obtain this product from its manufacturer for the larger trial and therefore chose to try to produce a duplicate product. It is not clear to what extent the researchers were actually successful in replicating an exact match of Remifemin, claims ABC.
Remifemin has been shown effective in numerous clinical trials, including a larger and longer trial just published in Obstetrics and Gynecology (2005;105:1074-83), it added.
This randomized, multicentre, double-blind, placebo-controlled trial on 304 menopausal women demonstrated that 40 mg of the German black cohosh preparation produced clinically significant benefits, particularly in women in early stages of menopause, with no significant adverse side effects.
"Most of the clinical trials published to date on black cohosh have demonstrated positive results in helping to treat various symptoms of menopause," said Mark Blumenthal, founder and executive director of ABC. "The evidence supporting the benefits and relative safety of this traditional herb is becoming increasingly clear."
At least 14 clinical trials on black cohosh preparations support their safety and efficacy in treating menopause-related symptoms, including hot flashes, perspiration and mood swings, according to Gail Mahady, assistant professor of Pharmacy Practice at the University of Illinois at Chicago, who has reviewed most of the research on black cohosh for a monograph for the World Health Organization.
