High intakes of Isoflavone-rich soy foods are associated with delayed menstrual cycle and lower breast cancer risk in premenopausal women.
This study examined the effect of isoflavone-rich soy protein on menstrual cycle and breast cancer risk in premenopausal women. Researchers fed 6 females with soy protein containing 45 mg of isoflavone for 1 month.
Researchers discovered that high consumption of soy protein increased serum concentrations of estradiol in the follicular phase and delayed menstrual cycle. Reduced plasma levels of cholesterol, luteinizing, and follicle-stimulating hormones were found in all the subjects during their ovulation period. In this study, these actions of isoflavone were linked to low breast cancer incidence, commonly found in Chinese and Japanese women who consumed large quantities of soy foods.