Hot Flash News Flash: The Soy Myth

Around age 30, women’s estrogen levels begin to drop. Estrogen plays an important role for women to maintain healthy, strong bones. It has been hypothesized that increasing soy intake may help minimize bone loss in post-menopausal women, and therefore provide a safer alternative therapy to hormone replacement. However, a recent meta-analysis in the Journal of Women’s Health found otherwise.

Soy is a large part of traditional Asian cuisine, and as such, researchers often cite the soybean to explain why Asian women have relatively low incidence rates of osteoporosis, despite lower intake of dairy products, when compared to Western women.  Soy contains plant compounds called “phytoestrogens,” a class of which are called isoflavones.  These isoflavones have structures similar to estrogen, and as such, can mimic its action in our bodies.

Due to these estrogenic properties, the isoflavones found in soy are of particular interest to post-menopausal women. During menopause, estrogen levels naturally decrease.  Lower levels of estrogen are associated with lower bone mineral density, and therefore, an elevated risk of developing osteoporosis.

The study included 12 randomized, controlled trials which examined supplementation of isolated soy isoflavones and its effect on bone mineral density in peri- and post-menopausal women.  Sample sizes and study durations varied greatly, but as a body of research, they spoke louder than each individual study could ever on its own.  Of the 12 studies, seven found no significant effect on bone mineral density with isoflavone supplements compared to placebo, while five of the studies did.  Based on the pooled data, the authors found that evidence does not support a benefit of isoflavone supplements on bone mineral density.

These studies were not without their flaws. Several of the participants dropped out of the study due to upset stomach from the supplements, or just simply not liking the taste of the food provided.

One isoflavone in particular, genistein, showed potentially promising results, however. In two of the studies, genistein was supplemented apart from the other soy isoflavones as opposed to being given in a mixture of many different isoflavones.  This difference in dosing appears to have affected the outcomes.  In studies in which genistein was given as a mixture, no significant benefits on bone density were noted.  But in one of the two studies in which genistein alone was supplemented, the women in the test group had significantly higher bone mineral density measurements than those in the placebo group.

Based on these findings, the authors suggested that genistein, when supplemented alone, may be a promising therapy in improving bone mineral density, but significantly more research would be needed to validate these findings and identify what dose, if any, would be considered safe and efficacious.  Alas, the supplement industry may be jumping the gun. Citracal already has a product on the market called Citracal Bone Density Builder, which contains genistein.  The company claims that genistein can increase bone density by up to 5 percent, although no source material for this claim is noted on the company’s website.

In the meantime, the saga regarding bone health continues. We’ve investigated dietary factors which can improve or hinder your bone strength, and covered the controversy related to calcium supplements. As always, it’s important to talk to your doctor before adding any new supplements to your diet.

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