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Black Cohosh a Bust for Hot Flashes

Millions of women have taken black cohosh to reduce hot flashes and other menopause-related symptoms, but the most rigorous study of the herbal supplement ever conducted shows no evidence that it works.
WebMD Health News
Reviewed by Louise Chang, MD

Dec. 18, 2006 -- Millions of women have taken black cohosh to reduce hot flashes and other menopause-related symptoms, but the most rigorous study of the herbal supplement ever conducted shows no evidence that it works.

The federally funded trial was designed to compare black cohosh to other herbal supplements, traditional hormone therapy, and placebo treatment for menopausal symptoms.

Hormone therapy was the only treatment that clearly reduced hot flashes, night sweats, and other related symptoms.

The study appears in the Dec. 19 issue of the journal Annals of Internal Medicine.

"Our finding that black cohosh did not work will be disappointing news to many women," researcher Katherine M. Newton, PhD, tells WebMD. "It would be nice to find a clearly effective alternative to hormone therapy."

Looking for Alternatives

Most women experience hot flashes and related symptoms around the time of menopause, which typically occurs between ages 45 and 55.

Hormone therapy involving estrogen or estrogen plus progestin is very effective for reducing hot flashes, but concerns about safety have caused millions of women to abandon the treatment.

Those concerns appeared to be bolstered late last week with the news of a dramatic drop in breast cancers among American women.

Although the reason for the drop is not yet clear, many experts speculate that it is related to the decline in hormone use following the 2002 publication of the Women's Health Initiative study, which found an increase in both breast cancers and heart problems among users.

Many symptomatic women turned to black cohosh and other herbal supplements when they stopped taking hormones, but few well-designed clinical trials have been done evaluating the effectiveness of these products.

Studying Treatments for Menopause Symptoms

In an effort to address this, Newton and colleagues with the Seattle-based health care system Group Health Cooperative recruited 351 menopausal and newly postmenopausal women for their study.

The women were between the ages of 45 and 55 when they entered the trial, and all were experiencing at least two menopause-related symptoms a day.

Without knowing which treatment they were getting, all of the women took one of five therapies for a year. The treatments were:

  • Black cohosh alone (160 milligrams daily)
  • A combination herbal supplement that included 200 milligrams of black cohosh daily, plus alfalfa, boron, dong quai, ginseng, and other herbal ingredients
  • A combination herbal supplement that did not include black cohosh but did include recommendations to increase the consumption of soy-based foods
  • Traditional hormone therapy
  • Placebo

The researchers found no significant difference in the number of daily hot flashes experienced by women on any of the treatments, with the exception of hormone therapy.

Women taking herbal supplements had an average of half a hot flash a day less than women taking placebo -- an amount not considered significant. By comparison, the women on hormone therapy had about four fewer hot flashes a day.

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