SEATTLE—The popular herbal supplement black cohosh does not relieve hot flashes among women going through menopause, according to a study by researchers from Group Health Cooperative, a Seattle-based health care system.
Published in the December 19 issue of the Annals of Internal Medicine, this study is the first of its kind to compare various forms of black cohosh to a placebo and to hormone therapy (estrogen with or without progestin).
"Black cohosh used alone or as part of a multibotanical supplement shows little potential as an important therapy for relief of hot flashes," the researchers concluded. The herbal interventions were no better than placebo. Hormone therapy, on the other hand, significantly reduced the frequency of hot flashes.
"We were disappointed by the findings because many women want an alternative to hormone therapy, and many have assumed that black cohosh is a safe, effective choice," said Katherine M. Newton, PhD, associate director of Group Health Center for Health Studies and the principal investigator of the study. "While hormone therapy is still the most effective treatment for hot flashes, recent studies have shown that it poses serious risks."
Newton estimates that 80 percent of women experience hot flashes around the time of menopause, which typically happens between ages 45 and 55. The average age of menopause is 51.
To conduct the study, the researchers randomly assigned 351 peri-menopausal or post-menopausal women, aged 45 to 55, to one of five therapies:
4) menopausal hormone therapy (estrogen with or without progestin)
The study was double-blinded, meaning that the study participants and the staff did not know which treatment was assigned to any given woman. Evaluating the women at three, six, and 12 months, the researchers found no significant difference between the numbers of daily hot flashes in any of the herbal supplement groups when compared to the placebo group. Specifically, women taking the herbal treatments reduced their hot flashes by about one half an episode per day when compared to women taking the placebo. The women taking hormone therapy reduced their hot flashes by about bout four episodes per day when compared to placebo.
"Prior to our study, the trials of black cohosh were small and of short duration," explains Susan Reed, MD, MPH, co-investigator and professor of obstetrics and gynecology at the University of Washington. "Our study was the largest and longest to date. Plus, we had good controls with both the placebo and hormone therapy arms, allowing us to definitively show differences between the groups taking herbs and the placebo group."
With no strong evidence that herbal alternatives work for hot flashes, Newton suggests several behavioral changes women can make. These include dressing in layers, sleeping in a cooler room, keeping ice water and a fan nearby, and avoiding possible triggers such as very hot liquids and alcohol.
Newton also notes that hot flashes decreased during the 12-month course of participation in all the study groups, including the placebo group. "We call this the ‘tincture of time'—that is, over time, hot flashes nearly always go away on their own," Newton said.
The study was funded by the National Institute on Aging and the National Center for Complementary and Alternative Medicine.
In addition to Reed, co-investigators were Andrea LaCroix, PhD, Louis Grothaus, MS, Kelly Ehrlich, MS, of Group Health; and Jane Guiltinan, ND, of Bastyr University.
Group Health Cooperative
Founded in 1947, Group Health is Seattle-based, consumer-governed, nonprofit health care system that coordinates care and coverage. The Group Health Center for Health Studies conducts research related to prevention, diagnosis, and treatment of major health problems. It is funded primarily through government and private research grants.
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