Factors to Consider in the Association Between Soy Isoflavone Intake and Breast Cancer Risk

Chisato Nagata

doi:10.2188/jea.je20090181

Abstract

It has been suggested that soy isoflavones have protective effects against breast cancer. However, data from epidemiological studies are not conclusive. A recent meta-analysis showed that soy intake was inversely associated with breast cancer risk in Asian but not Western populations, which indicates that protection against breast cancer may require that women consume levels of soy typical in Asian diets. In addition to the amount of soy isoflavones consumed, the form and food source of isoflavones, timing of isoflavone exposure, estrogen receptor status of tumors, and equol-producer status and hormonal profile of individuals may modify the association between soy isoflavone intake and the risk of breast cancer. These factors might explain the heterogeneity of results from studies. This present report contrasts background data from Japanese and Western women to identify the potential modifying of these factors.

Highlights

There has been much interest in the potentially protective role of soy in breast cancer development
Isoflavones have been shown to be anti-proliferative,[3] proapoptic,[4] antiangiogenic,[5] anti-oxidative,[6] and anti-inflammatory.[7]. These findings indicate that soy isoflavone may be a potent agent for preventing breast cancer
6 studies have assessed the association of soy or isoflavone with breast cancer risk, with regard to the estrogen receptor status of tumors.[34,64,65,66,67,68]