Hot flashes—a review of the literature on alternative and complementary treatment approaches

Alternative Medicine Review, August, 2003 by Hazel A. Philp

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Phytoestrogens are derived from dietary and botanical sources (Table 2). Major sources of dietary lignans include flaxseed and whole grain cereals, while legumes, such as soybeans and chickpeas, are major sources of isoflavones, and clover, alfalfa, and soybean sprouts are sources of coumestans. (5) Phytoestrogens are currently the most popular alternative to HRT. (42)

A relatively small but growing number of clinical trials have evaluated the role of phytoestrogens in relieving hot flashes associated with menopause. Most randomized, double-blind, placebo-control led trials indicate favorable reductions in the frequency, duration, and/or severity of hot flashes.

Soy Isoflavones and other Soy Products

Several published studies report improve merits in hot flashes with soy protein, soy foods, or soy isoflavone extract. In a randomized, double-blind, placebo-controlled study, 75 postmenopausal women (55 completed the study) experiencing at least seven hot flashes daily received either soy isoflavone extract (total of 70 mg genistin, the aglycone form of genistein, and daidzin, the aglycone form of daidzein, per day) or placebo. (43) After 16 weeks, women taking the soy extract had a 61-percent reduction in daily hot flashes, versus a 21-percent reduction in the placebo group. "Responders" (defined as patients whose hot flashes were reduced by at least 50 percent at the end of the treatment period) included 66 percent in the soy extract group and 34 percent in the placebo group.

Upmalis et al examined the safety and efficacy of an oral soy isoflavone extract on 177 postmenopausal women (mean age 55 years) experiencing live or more hot flashes per day. (44) In this double-blind, placebo-controlled study the women were randomized to receive either soy isoflavone extract (total of 50 mg genistin and daidzin per day) or placebo. Analysis after 12 weeks showed a statistically significant reduction in average hot flash severity and frequency in the soy isoflavone group compared with the placebo group. In addition, decreases in the incidence and severity of hot flashes occurred as soon as two weeks in the soy group; whereas, the placebo group experienced no relief the first four weeks. Endometrial thickness, measured by ultrasound, did not change in either group.

In another randomized, double-blind, crossover study, a statistically significant decrease in hot flashes occurred in 51 menopausal women consuming 20 g soy protein (containing 34 mg isoflavones) in single or split dosages compared to placebo (20 g complex carbohydrates). (45) After six weeks, a significant improvement was observed for the perceived severity of vasomotor symptoms (i.e., hot flashes) in both soy groups compared with placebo, although in the "twice dally" group the effect was greater. This suggests having consistent circulating levels of phytoestrogens may be more efficacious than a single higher dose. In addition significant improvements in lipid and lipoprotein levels, as well as blood pressure, were noted in the treatment groups.