Isoflavones extracted from soy have estrogenic effects, and on this basis they have been advocated for treating menopausal symptoms. However, studies that used isoflavones for this purpose have returned mixed results, with some trials showing marked benefits and others showing no benefits at all. Several theories have been put forth to explain these discrepancies. One of the leading candidates points to differences between soy isoflavone extracts.
There are three major isoflavones found in soy: genistein, daidzein, and glycitein. Each of these isoflavones can occur in two types or states. The first type, predominant in raw soy products, is called an “isoflavone glycoside.” In an isoflavone glycoside, the isoflavone is attached to a sugar-like substance known as a “glycone.” The second type, predominant in fermented soy products, is called an “isoflavone aglycone.” These consist of isoflavones without a glycone attached, and are also called “free isoflavones.”
A study published in the journal Menopause tested the effectiveness of an isoflavone product rich in the aglycone form of daidzen (DRI). In this double-blind, placebo-controlled study, 190 menopausal women were given either placebo or one of two doses of DRI (40 mg or 60 mg) daily for a period of twelve weeks. Participants kept a diary of the frequency of their hot flashes, and this was the primary means used by researchers to gauge outcomes.
The results indicated that both the 40 mg and 60 mg doses of DRI were equally effective in reducing hot flashes, reducing them by approximately 50%. By comparison, in the placebo group, hot flash frequency decreased by only 39%. This difference just missed standard cut-off for statistical significance when the two DRI groups were considered separately, but when they were combined the difference did become significant.
These are promising findings. However, the necessity of such careful statistical parsing suggests a relatively low level of effectiveness.
One limitation of this study was a relative high dropout rate: only 77% of the women completed the study. Another problem is that it didn’t compare this particular daidzen-aglycone-rich isoflavone against any other form of isoflavones.