A recent study suggests the herb does not relieve symptoms of menopause; the American Botanical Council issues a response, citing the wealth of research supporting its use.
As the public increasingly turns to herbal and nutritional supplements as alternative or adjunct treatments to conventional Western medicine, it's important that all health care providers give patients an accurate picture of the efficacy and safety of those supplements. While clinical/experiential evidence might lead you to utilize a particular herb in the treatment of particular conditions or patients, what happens when the latest research shows otherwise?
Results of the Herbal Alternatives for Menopause Study (HALT), published recently in the Annals of Internal Medicine, suggest that black cohosh, whether used alone or in conjunction with other botanical supplements, does not relieve hot flashes in postmenopausal women or those approaching menopause. The study was funded by the National Institute on Aging (NIA) and the National Center for Complementary and Alternative Medicine (NCCAM), both components of the National Institutes of Health (NIH). Katherine M. Newton, PhD, of the Group Health Center for Health Studies in Seattle and the University of Washington, led the investigation. The 12-month randomized, double-blind, placebo-controlled trial compared several herbal regimens and menopausal hormone therapy (estrogen with or without progesterone) to placebo in 351 women ages 45 to 55.
"In recent years, scientific studies have raised questions about the safety of certain types of menopausal hormone therapy in some women. Interest has grown in alternatives to hormones, including herbal supplements, for controlling hot flashes and other symptoms of menopause," said NIA Director Richard J. Hodes, MD. "Testing the safety and efficacy of various treatments in randomized clinical trials such as HALT is critically important in helping women in mid-life and their doctors to make informed choices."
Following the publication of the HALT study, the American Botanical Council (ABC) issued a response stating that the study findings were contradictory to the majority of results from other studies of black cohosh. Mark Blumenthal, executive director of the ABC, faulted the design of the study and said the findings were at odds with existing evidence about black cohosh. In an interview with Reuters News, he said, "It is definitely not the last word on the subject."
In the original study by Newton, et al., 351 women were randomized to five groups: 160 mg of black cohosh daily; a multi-botanical with black cohosh, 200 mg daily; a multi-botanical and dietary soy counseling; estrogen, 0.625 mg daily; and placebo. The researchers found no significant difference between the placebo or any of the herbal formulations in alleviating symptoms of menopause, such as hot flashes and night sweats.
The ABC's official response regarding the HALT study results is excerpted as follows. The full text of the release is available on the council's Web site.
American Botanical Council Clarifies Recent Clinical Trial
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.1
"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, the leading herbal nonprofit research and education organization.
Numerous 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 assistant 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."
Dr. Mahady, one of the principal authors of the black cohosh monograph for the World Health Organization, has reviewed these trials in several journal publications.2,3 She added, "Thus, one negative study does not neutralize all of the other 10 positive trials."
Although this study appears to be the longest placebo-controlled trial on black cohosh and one of the largest, there are still some potentially serious limitations, which the trial authors have acknowledged. By dividing the total number of women into 5 groups (arms) to test 4 different therapies (including HRT) against placebo, the number of women in each group drops to a point where the statistical significance of the outcomes (whether positive or negative) are greatly diminished. The authors wrote, "The study was too small to detect small changes in symptom frequency (less than 1.5 hot flashes per day)."1
Dr. Hardy also noted that "despite the relatively large number of participants, the complex design (5 arms) means that each group had relatively few participants and thus the study was not powered to find any but large effects." The trial had set a criteria for inclusion at a minimum of 2 hot flashes per day, a relatively low level at which reductions are more difficult to produce and/or monitor in a trial like this (although the actual median level was actually 6).
In a corresponding editorial, Carol M. Magione, MD, MSPH of the David Geffen School of Medicine in Los Angeles wrote, "Black cohosh is not effective" - basically relying on this trial as the sole arbiter of the efficacy of black cohosh.4 Dr. Mangione's conclusion contrasts with other randomized controlled trials (RCTs) that have shown measurable efficacy for the two most well-researched black cohosh preparations (e.g., Remifemin® and Klimadynon®, both from Germany). At least 15 clinical trials attest to the efficacy of Remifemin (Schaper and Bruemmer, Salzgitter, Germany, imported by Enzymatic Therapy, Green Bay, WI) and 6 do so for Klimadynon® (Bionorica, Neumarkt, Germany, imported by Bionorica USA, Eugene, OR).
Several experts noted that some information on this trial has been published previously. According to Dr. Hardy, "This is the second time data from this trial has been reported in the medical literature, so care must be taken not to count this study twice in looking at the whole body of literature."
Referring to the relatively large placebo response in this trial (about 30% of the women on placebo reported beneficial effects, Dr. Hardy stated that "Research in menopausal treatments, besides estrogen, are often confounded by very large placebo effects."
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."
Dr. Fabricant also noted that a potentially significant flaw in the trial is the lack of data on secondary trial outcomes in this article: "Vaginal cytology; serum lipids (total cholesterol, HDL and LDL cholesterol, triglycerides); bone mineral density (hip and spine dual energy X-ray absorptiometry scan); glucose metabolism (insulin, fasting blood glucose); and coagulation factors (fibrinogen, PAI-1) would all provide valuable information regarding both the botanicals and the risks that have been seen with conjugated equine estrogens (CEE) in previous studies."
Another question about the study was raised by Francis Brinker, ND, of the University of Arizona Program for Integrative Wellness and author of several highly-regarded reference books on herbal medicine, including Herb Contraindications & Drug Interactions 3rd ed. Dr. Brinker states, "I do not have a problem with acknowledging the negative outcome, but I reject the extrapolation of the results to all forms of black cohosh products. The more medical (and herbal) minds are challenged on this sort of lazy assumption, the sooner they'll recognize legitimate distinctions among various herbal preparations and their effects. Not all products from the same herb are created equal, so we shouldn't blame, say, Peter Cohosh for the failings of Paul Cohosh (or reward Peter for Paul's success), unless there is some good evidence for bioequivalency" - the ability to show that one preparation has the same physiological effect as another. That has not been demonstrated in this trial, so it is not possible to extend the results of this trial to other clinically tested black cohosh products.
Dr. Brinker also commented that the extract studied in this trial was a daily dose of 160 mg of a 70% ethanolic extract, whereas the positive studies with Remifemin tablets used 40 mg daily of a 40% isopropanolic extract in an amount equivalent to 40 mg of the herbal material.
Eckehard Liske, PhD, international medical director at Schaper & Bruemmer, the German company that manufacturers and markets Remifemin, the most clinically-researched black cohosh product, observed that the black cohosh product used in this trial did not appear to have met stability testing that should have been required of any herbal substance that was being employed for a 12-month trial. "This type of packaging does not protect the study medication as well as a blister packaging," he wrote. This was acknowledged by the trial authors in their writing that they were not able to detect several characteristic [chemical] marker substances. Thus, this absence of blistered medication, according to Dr. Liske, suggests a possible instability of the study medication (i.e., the black cohosh extract may have degraded in some manner over time).
Fredi Kronenberg, PhD, professor of clinical physiology at Columbia University College of Physicians and Surgeons, an expert in menopause, and author of a review paper on complementary and alternative approaches to menopausal symptoms,5 cautions that in science one must look at the whole body of research in a field.
"This study," she said, "must be considered in the context of the other studies over years of research on black cohosh, the majority of which have positive outcomes. This study has a negative outcome on hot flash frequency. But each study uses slightly different populations of women, some only postmenopausal women, some, like this study, examining both menopausal and peri-menopausal women. Half of the women in this study were peri-menopausal - with estrogen levels still fluctuating and thus impacting hot flashes. While the investigators did control for this in their analysis, it points out the challenges for interpreting results across studies."
Dr. Kronenberg, who is also a Trustee of ABC, continued, "Of critical importance when reviewing black cohosh studies is that we know little about how the different extraction techniques of black cohosh preparations and resulting formulations may impact hot flash physiology. The extract in this study was an ethanolic extract. There have been positive studies with both ethanolic and isopropanolic black cohosh extracts. We are in a phase of poorly funded research, so we must accumulate the results of many relatively small studies since we do not have any large studies underway at this time. The media does a disservice to the public by using catchy headlines and not taking the time for the in-depth ana-lysis so needed in reporting on what are complex issues."
In sum, Dr. Fabricant emphasized, "This new study should not be called conclusive by any stretch."
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