High soy intake and breast cancer risk

A review of high soy consuming Asians and the risk of breast cancer in 8 studies. The highest intake, 20 mg of isoflavones per day or more, was associated with the lowest risk. Decreased risk was not seen in studies in Western populations that had lower isoflavone intake.

Epidemiology of soy exposures and breast cancer risk.
Br J Cancer. 2008 Jan 15;98(1):9-14.