How Effective is Red Clover Extract for Hot Flashes?

Menopausal women who take an extract of red clover (Trifolium pratense) may experience a more rapid reduction in hot flashes, according to a new study in Journal of the American Medical Association (2003;290:207–14). However, the total number of hot flashes per day didn’t decrease any more in this group than it did in women taking a placebo, which calls into question whether red clover extract is really beneficial to menopausal women.

Hot flashes are the most common reason women visit their physicians for treatment of menopausal symptoms. The cause of hot flashes is not completely known, but may be in part due to a drop in estrogen levels. More than 70% of women in Western societies experience hot flashes at the onset of menopause, compared with less than 20% of women in Asian countries. Some scientists believe that the high consumption of soy in these countries accounts for the lower incidence of hot flashes but studies are inconclusive. Soy and red clover both contain substances called isoflavones, which are believed to have weak estrogen-like activity. The most common isoflavones found in red clover include genistein, daidzein, and biochanin A.

In the new study, 252 menopausal women between the ages of 45 and 60 years were randomly assigned to receive 82 mg per day of isoflavones from red clover, 57 mg per day of isoflavones from red clover, or a similar looking placebo for 12 weeks. All participants kept a daily diary to record the frequency and number of hot flashes.

The number of hot flashes was significantly lowered in those taking 82 mg per day of isoflavones, 57 mg per day of isoflavones, and placebo by 41, 34, and 36%, respectively. There was no statistically significant difference between the three groups, suggesting that red clover was no better than placebo at decreasing the number of hot flashes. However, women taking the higher amount of isoflavones experienced a more rapid reduction in the number of hot flashes compared with the women in the other two groups. That finding indicates that red clover does have biological activity and raises the possibility that other dosage regimens might be more effective. Those taking the higher amount of isoflavones did experience fewer hot flashes per day, compared with women taking placebo, but the reduction in hot flashes was not statistically significant. Obese women taking red clover isoflavones had a more pronounced drop in the number of hot flashes than thinner women, suggesting the benefits of red clover may be limited to women who are overweight.

Other small studies have shown that red clover isoflavones do reduce the number of daily hot flashes. It is not clear why women in the new study did not respond favorably. Possibly, the amount of red clover isoflavones used in the new study was too low to produce optimal results. Several studies suggest that isoflavones are cleared from the body relatively quickly; it may, therefore, be necessary to take the red clover extract more than once a day to realize benefits. While more research is necessary to determine the optimal amount and timing, red clover isoflavones are relatively safe and may help menopausal women feel more comfortable.

Darin Ingels, ND, MT (ASCP), received his bachelor’s degree from Purdue University and his Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. Dr. Ingels is the author of The Natural Pharmacist: Lowering Cholesterol (Prima, 1999) and Natural Treatments for High Cholesterol (Prima, 2000). He currently is in private practice at New England Family Health Associates located in Southport, CT, where he specializes in environmental medicine and allergies. Dr. Ingels is a regular contributor to Healthnotes and Healthnotes Newswire.

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