In a recent test, a pill containing soy and black cohosh was no better at curbing menopause symptoms than a fake pill.
The researchers don't dismiss plant estrogens (phytoestrogens). Instead, they raise a lot of questions in their report in Menopause.
Did the two plant estrogens they studied -- soy isoflavones and black cohosh -- cancel each other out? Did patients' hopes trigger a "placebo effect?" Was the study long enough?
Those issues will likely get more attention,with many women seeking menopausal treatments without prescription hormone replacement therapy, write the researchers.
They included Marieke Verhoeven, MD, of the obstetrics and gynecology department of Amsterdam's VU University Medical Center.
Verhoeven's study included 124 healthy women who had at least five menopausal hot flashes daily.
The women randomly got a phytoestrogen supplement or a fake pill (placebo) that only contained olive oil. They didn't know which pill they'd gotten.
The supplement contained soy extract, black cohosh, evening primrose oil, calcium, vitamin D, and vitamin E. The pills looked, smelled, and tasted exactly the same.
The women took the pills for 12 weeks. Data came from their menopausal symptom diaries, blood tests, and quality-of-life surveys.
Similar Results for Both Groups
Women in both groups reported similar improvements. The supplement apparently offered no advantage over the placebo.
That's why the researchers write that "the supplement was not effective" in easing the women's hot flashes.
Most women had taken the pills as instructed (89 percent of the placebo group and 97 percent of the supplement group), write Verhoeven and colleagues.
Daily hot flashes dropped 36 percent in women taking the fake pill.
Other phytoestrogen studies have also shown high response rates to placebos, write the researchers.
SOURCES: Verhoeven, M. Menopause, July/August 2005; vol 12: pp 412-420. News release, The North American Menopause Society.