Is Black Cohosh Effective for Hot Flashes?

Healthnotes Newswire (January 4, 2007)—A new study of the herb black cohosh has found that it is not effective for menopausal hot flashes. This is likely to come as disappointing news to the millions of women seeking effective alternatives to hormone replacement therapy (HRT). Although this was the largest study of its kind to test black cohosh, and funded by the National Institutes of Health, some natural medicine experts find flaws in the study’s design and argue that for some women black cohosh might still be a viable option for relieving symptoms.

The Herbal Alternatives for Menopause Trial (HALT) was designed to provide “rigorous evidence on the efficacy and short-term safety of commonly used naturopathic approaches for management of vasomotor symptoms.”

To this end, researchers enrolled 351 women ages 45 to 55 who had two or more menopausal symptoms daily; 52% of the women were transitioning into menopause (perimenopause) and 48% were postmenopausal. They were randomly assigned to receive one of five treatments for one year:

• 160 mg of black cohosh (Actaea racemosa; Cimicifuga racemosa) daily

• An herbal combination including 200 mg of black cohosh and nine other ingredients daily

• The same herbal combination plus advice to consume more soy products

• A type of HRT: 0.625 mg of conjugated equine estrogens (animal-derived) daily, with or without 2.5 mg medroxyprogesterone acetate daily

• An inactive substance (placebo)

A negative result for black cohosh

Menopausal symptoms, in particular hot flashes, did not differ between the herbal intervention and placebo groups, with one exception: at 12 months, symptoms were significantly worse among women taking the combination of herbs plus soy than among those taking placebo. The difference in symptoms per day between placebo and any of the herbal treatments at any time point within the year was less than one symptom per day. The study was published in the Annals of Internal Medicine, in which the authors concluded that black cohosh, used in isolation, or as part of a multibotanical regimen, “shows little potential as an important therapy” for relief of menopausal hot flashes.

The American Botanical Council described the study as “inconsistent with the positive outcomes for treating menopause symptoms seen in the majority of published clinical trials.” In response, Jane Guiltinan, ND, one of the authors on the study, points out that many of those studies were uncontrolled, short term, not randomized, and not double-blinded; had small numbers of participants; and were industry sponsored. “If you look at just those studies that were non–industry sponsored and that were placebo-controlled,” said Dr. Guiltinan, “the balance of results is negative for black cohosh.”

Despite the negative results, Guiltinan still uses black cohosh in her private practice. “I observe that it works in some women, especially if I use a higher dose. I also observe it does not work in a significant percentage of women, regardless of dose.” Guiltinan proposes that there may be responders and nonresponders to black cohosh, beyond the placebo effect.

Was the study flawed?

The authors acknowledged that the trial “did not simulate the whole-person approach used by naturopathic physicians.” But according to critics, the study also falls short of examining black cohosh as a single therapy.

“They tried to study too many things,” said Donald J. Brown, ND, a naturopathic physician, author of Herbal Prescriptions for Health and Healing, and founder of Natural Product Research Consultants. “Including so many treatment groups means there are fewer people in each group, and that reduces the statistical power of the study to demonstrate an effect of black cohosh.”

The authors themselves acknowledged this limitation in their paper. However, Guiltinan added, “The number of participants in this study was adequate to demonstrate statistical significance if the effect in the herbal arms was as little as 50% of the observed effect of conventional hormone therapy.”

Tori Hudson, ND, is a naturopathic physician, author of The Women’s Encyclopedia of Natural Medicine, and founder of Vitanica, a company that makes dietary supplements for women. Like Dr. Brown, she points to problems with the statistics in the study. “And there are differences between in-office practice and the mail questionnaires they used,” Dr. Hudson added. “They used less-than-ideal ingredients, and probably had unreasonable expectations of compliance with adding soy foods to the diet.”

Hudson also faults the study for comparing perimenopausal women with inconsistent symptoms to postmenopausal women. But Guiltinan says, “Very careful sensitivity analyses were conducted to determine whether age, severity of symptoms, or other variables may have affected the outcomes. No differences were seen when peri- and postmenopausal women were analyzed separately, nor were differences observed when data were analyzed by frequency of symptoms per day.”

Is this the last word?

Both Hudson and Guiltinan agree that the multiherb formula would have been better had it included herbs with more evidence of efficacy for treating hot flashes (for example, Hudson suggests a combination of black cohosh, red clover, and kava). This is a difficulty that sometimes occurs when practice guidelines change rapidly and the long process of designing, funding, carrying out, and publishing research cannot keep pace. “When this grant was originally written in the midnineties,” Guiltinan said, “the multibotanical product chosen was very commonly used by naturopathic doctors in the Puget Sound area.”

Brown also questioned the amount of black cohosh used in the study, which was four times the amount proven effective in previous research. There have been several clinical trials of black cohosh for menopausal symptoms since 2003, all of which reported positive results using only 40 mg per day. Guiltinan cautioned against comparing those previous results to those of the HALT study. “Most of those studies were uncontrolled and had small numbers of participants,” she said. “Moreover, the observed placebo response for vasomotor symptoms of menopause is huge, about 40 to 45% as evidenced by many studies over many years. This fact alone should make any uncontrolled study suspect.”

Regarding the discrepancy in the amount of black cohosh extract used, Guiltinan defended the HALT study’s protocol: “We used 160 mg per day because, in my experience in treating menopausal women, it is often necessary to increase the dose to see much benefit.”

“In the end,” Hudson concluded, “it was a disappointing result for black cohosh.”

(Ann Intern Med 2006;145:869–79; Obstet Gynecol 2005;105:1074–83; J Women Health Gender Based Med 2002;11:163–73)

Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.

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