Breast cancer, estrogen, soy genistein, and other dietary factors

Purpose The purpose of this literature review is to examine underlying mechanisms through which soy may affect breast cancer risk. Design/methodology/approach The approach taken is to summarize the emerging mechanisms of how isoflavones, such as genistein, interact with processes leading to breast cancer. Findings The key finding of this analysis is that these mechanisms include a multitude of contrasting effects of genistein on estrogenic and non‐estrogenic signaling pathways controlling cell growth. Furthermore, several of these mechanisms are also regulated by additional dietary factors, such as omega‐3 fatty acids (found e.g. in fish) and various other phytochemicals (factors found generally in plant‐based foods). The available mechanistic information supports (i) a potent effect of dietary factors on cell growth and (ii) a synergistic effect of different dietary components, such as soy, fish, and plant‐based foods. Practical implications In conclusion, the practical implication of this analysis is the conclusion that the mechanistic information available at this time does not support a recommendation for an isolated increase in soy to decrease breast cancer risk. Originality/value This article should be of value for health care providers, nutritionists, and consumers.