Daidzein-rich isoflavones improve hot flash frequency and severity.
Daidzein-rich isoflavone aglycones (DRIs), 40 or 60 mg a day, improved hot flash frequency and severity by about 40% after 8 weeks of treatment and by about 50% after 12 weeks, without causing any significant changes in endogenous sex or thyroid hormones.
The findings come from a randomized, double-blind, placebo-controlled trial involving approximately 150 menopausal women between the ages of 38 and 60 years. The two active groups were given an isoflavone-rich supplement made from soy germ. The researchers calculated that 40- and 60-mg DRIs reduced hot flash frequency by 43% and 41%, respectively, at 8 weeks versus 32% for placebo (P not significant). At 12 weeks, the reductions were 52%, 51%, and 39% for 40-mg DRIs, 60-mg DRIs, and placebo, respectively (P=.07 and .09 vs. placebo).
Reports about isoflavones effectively treating menopausal symptoms have been conflicting. Reasons for the inconsistencies may include differences in methods used to isolate isoflavones, concentrations of bioavailable isoflavones, or the composition of isoflavones used. Since no studies have reported harmful effects of isoflavones on menopausal symptoms, they may represent an alternative or adjunct to hormone therapy.