The researchers compared the four isoflavones to a traditional bisphosphonate treatment, risedronate and estrogen plus progesterone. These traditional therapies decreased bone loss 22 percent to 24 percent, but only soy isoflavones from the cotyledon and germ significantly decreased bone loss by 9 percent and 5 percent, respectively. The findings are available online and will be published in the October edition of the Journal of Clinical Endocrinology and Metabolism.

The findings also indicate that the soy cotyledon was more effective because of its higher genistein content. Weaver's team is currently evaluating the role of genistein more closely.

"Before, we might have assumed that any isoflavone was equally effective, but we found that for a supplement to work it was because of the genistein content specifically," she said.

Source: Purdue University