Black cohosh same as placebo for hot flushes, says study
cohosh supplements, say results from the largest and longest trial
for the herb to date.
The 12-month randomized, double-blind, placebo-controlled Herbal Alternatives (HALT) for Menopause Study, funded by the National Institute on Aging (NIA) and the National Center for Complementary and Alternative Medicine (NCCAM), looked at the effects of several herbal regimens and menopausal hormone therapy (oestrogen with or without progesterone) in women ages 45 to 55.
Writing in the Annals of Internal Medicine, lead author Katherine Newton said: "Black cohosh used alone or as part of a multi-botanical supplement shows little potential as an important therapy for relief of hot flashes."
Black cohosh (referred to by the European Medicines Agency, or EMEA, as Cimicifugae racemosae rhizome) is a member of the buttercup family, and is a perennial plant native to North America. It has a long history of use for by women to reduce menopausal symptoms such as hot flushes.
Historically it has been a popular alternative to hormone replacement therapy (HRT) in many countries including the UK, where it is estimated that 9 million days worth of black cohosh supplements were purchased in 2004.
The new study randomly assigned 351 pero-menopausal or post-menopausal women (age range 45-55) to one of five intervention groups: black cohosh (160mg daily); multi-botanical supplement (black cohosh (200 mg daily), alfalfa, boron, chaste tree, dong quai, false unicorn, liquorice, oats, pomegranate, and Siberian ginseng); the multi-botanical supplement plus diet counselling to increase consumption of soy; menopausal hormone therapy (oestrogen with or without progesterone); or placebo.
The women were evaluated after three, six, and 12 months of intervention, and the researchers report that the herbal supplements reduced the daily occurrence of the hot flushes by 0.6 episodes per day. However, this was not statistically significant, they said.
On the other hand, the women receiving the hormone therapy significantly reduced the number of hot flushes by about four episodes per day when compared to placebo.
Newton said that the researchers were disappointed by the results, since many women seek an alternative to hormone therapy, and many have assumed that black cohosh was a safe, effective choice.
"While hormone therapy is still the most effective treatment for hot flashes, recent studies have shown that it poses serious risks," she said.
Acting director of the NCCAM, Ruth Kirschstein, said: "While this study found that black cohosh alone or with other herbs did not reduce menopausal hot flashes, it highlights the importance of studying herbs using well-designed research to find out what works and what does not.
"With this information women and their physicians can have a meaningful discussion of complementary and alternative medicine approaches to menopause."
However, Mark Blumenthal, executive director of the American Botanical Council, told Reuters Health that the design of the study was faulty and pointed out that the results were inconsistent with the majority of science about black cohosh and menopause.
"It is definitely not the last word," he said.
Daniel Fabricant, vice president, scientific affairs for the US-based trade association Natural Products Association (NPA), echoed Blumenthal when he told NutraIngredients.com: "This study should not be determined as conclusive by any stretch."
"Over 3,000 women have been randomized for clinical trials using black cohosh for climacteric/vasomotor symptoms, and the weight of the evidence from those studies has been overwhelmingly positive," he said.
"It is disappointing that none of the data on the secondary outcomes of the study were included in the 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," said Fabricant.
According to the American Herbal Products Association's (AHPA) most recent Tonnage Survey of Select North American Wild-Harvested Plants, the herb was the second most harvested plant, with 159 tons from wild sources and 0.2 tons from cultivated sources.
Source: Annals of Internal Medicine Volume 145, Issue 12, Pages 869-879 "Treatment of Vasomotor Symptoms of Menopause with Black Cohosh, Multibotanicals, Soy, Hormonal Therapy, or Placebo: A Randomized Trial" Authors: K.M. Newton, S.D. Reed, A.Z. LaCroix, et al.
