High intake of diets rich in genistein-containing isoflavones may decrease Japanese women susceptibility to breast cancer.

This study examined the relationship between serum concentrations of specific isoflavones, such as genistein and diadzein, and breast cancer risk in Japanese women. Researchers estimated the plasma levels of genistein and diadzein in 24,226 women between the ages of 40-69 years, all of whom were recruited from the Japan Public Health Center-based Prospective Study Group. The breast cancer hazard ratios of all the subjects were also measured.

Researchers found a low prevalence of breast cancer among subjects with high circulating levels of genistein. According to this study, plasma diadzein concentrations did not have any significant effect on breast cancer risk. The results of this study show that increased dietary exposure to genistein-containing foods may decrease the odds of developing breast cancer in Japanese women.