July 8, 2003 -- Dietary supplements containing red clover aren't likely to cool hot flashes or provide an effective alternative to hormone therapy for women seeking relief from menopausal symptoms. A major new study shows the widely advertised supplements containing plant-based, estrogen-like substances called isoflavones are no more effective than a placebo pill in reducing hot flashes.
The study appears in the July 9 issue of The Journal of the American Medical Association.
Researchers say hot flashes are the main reason women seek medical help for menopausal symptoms. Until recently, hormone replacement therapy (HRT) had been the standard treatment for hot flashes and other menopause-related symptoms. But since the Women's Health Initiative and other studies have shown that HRT can increase a woman's risk of breast cancer and heart disease, there has been a heightened need for effective alternatives to HRT in reducing symptoms and improving the quality of life for postmenopausal women.
Researchers say dietary supplements containing isoflavones derived from red clover or soy have been heavily marketed as alternative treatments for menopausal symptoms. Isoflavones are plant estrogens that have estrogen-like activity in the body. Isoflavones are the most common form of plant estrogens.
Although previous studies have examined soy-based supplements, researchers say less is known about isoflavone supplements derived from red clover, which contain additional isoflavones not found in soy that may have some effect in reducing hot flashes.
Putting Red Clover to the Test
In this study, researchers compared the effects of two different commercial red clover extracts, Promensil (82 mg of isoflavones per day) and Rimostil (57 mg of isoflavones per day), vs. a placebo in reducing hot flashes among 246 postmenopausal women who were experiencing at least 35 hot flashes per week.
After 12 weeks of treatment, the study found no differences in reducing the average number of hot flashes reported by the three groups. Women who received Promensil reported an average of 3.4 hot flashes per day compared with 2.7 per day for the Rimostil group and 2.8 for those on the placebo.
By the end of the study, the average percent reduction in hot flashes was also similar across the groups. Women who took Promensil reported a 41% reduction vs. 34% in the Rimostil and 36% in the placebo group.
But researcher Jeffrey A. Tice, MD, of the University of California, San Francisco, and colleagues say Promensil reduces hot flashes more rapidly than the placebo or Rimostil.
The study also looked at how the red clover-based treatments affected the women's quality of life and found no major differences compared with placebo.
Researchers say heavier women seemed to benefit more from the isoflavone supplements than others but more research is needed to determine why.
"In conclusion, the overall reduction in hot flashes after 12 weeks of treatment was modest and similar between women in all 3 groups," write the researchers. "Although the study provides some evidence for a biological effect of Promensil, neither supplement had a clinically significant effect on hot flashes or other menopausal symptoms when compared with placebo."
SOURCE: The Journal of the American Medical Association, July 9, 2003.