Effects of soy isoflavones on breast cancer risk

 

The effects of soy isoflavones on breast cancer risk are controversial, with evidence supporting both estrogen agonist and antagonist properties.  

In our study we used an established postmenopausal primate model to investigate whether these effects are mediated by estrogen context.  Different doses of soy isoflavones were given within either a low or high postmenopausal estrogen environment.  The primary endpoint was breast epithelial proliferation.  Dietary isoflavones had minimal to no effect in the low estrogen environment but significantly blocked estrogen effects in the high estrogen environment, suggesting that dietary soy isoflavones may exert antiestrogen effects on breast tissue.  

Our results identify key isoflavone dose relationships and establish that estrogen context is a critical determinant of isoflavone effects.  This information should provide context for future clinical trials on soy isoflavones and breast cancer prevention.

 

Bibliographical reference:

Woood CE et al.: "Dietary soy isoflavones inhibit estrogen effects in the postmenopausal breast", Cancer Res. 2006 Jan 15;66(2):1241-9

 

Charles E. Wood

 

Department of Pathology / Comparative Medicine, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem , North Carolina, USA