A study conducted with 403 postmenopausal women has found that daily supplementation with 120 mg soy isoflavones reduces whole-body bone loss.

The 403 women were randomly assigned to receive either 80mg or 120mg of soy isoflavones plus calcium and vitamin D or an inert dummy tablet. Neither the participants nor the researchers were aware until the study end of which tablets the women were taking. The study was conducted over two years; the participants were assessed annually, changes in whole-body and regional bone mineral density (BMD), bone mineral content (BMC), and comparisons with average young adults at peak bone density were recorded. Changes in markers of bone metabolism in blood were also assessed. At the end of one year daily supplementation with 120 mg soy isoflavones was associated with a significantly smaller reduction in whole-body bone mineral density (BMD) compared to women supplemented with placebo. No effect was found on regional bone density or bone mineral content.

Isoflavones are phytoestrogens, plant compounds that are structurally similar to oestrogen; soy and red clover are rich sources. Isoflavones and other phytoestrogens can bind to estrogen receptors, mimicking the effects of estrogen in some tissues and antagonizing (blocking) the effects of estrogen in others.

Click here to read the study abstract.