Associations of intakes of fat, dietary fiber, soy isoflavones, and alcohol with levels of sex hormones and prolactin in premenopausal Japanese women.

OBJECTIVE: Endogenous sex hormones have been implicated in the etiology of breast cancer. Dietary factors such as fat, dietary fiber, soy isoflavones, and alcohol have been suggested to influence endogenous estrogen and other steroid hormone levels. We examined the relationship among these dietary factors and plasma sex hormone levels in premenopausal Japanese women.
METHODS: We measured the plasma concentrations of estradiol, estrone, testosterone, dehydroepiandrosterone sulfate, sex hormone-binding globulin, a follicle-stimulating hormone, a luteinizing hormone, and prolactin among 393 premenopausal women who had regular menstrual cycles fewer than 40 days apart. The dietary intakes were estimated with a validated food frequency questionnaire.
RESULTS: After controlling for age, BMI, phase of the menstrual cycle, number of births, age at first birth, history of breastfeeding, and smoking status, the saturated fat intake was significantly positively associated with total estradiol and free estradiol levels. Intakes of the other types of fat, dietary fiber, soy isoflavones, and alcohol were not significantly associated with levels of any hormone measured.
CONCLUSIONS: These data suggest that a high intake of saturated fat is associated with increased estradiol levels in premenopausal Japanese women. Saturated fat intake may have implications in the etiology of breast cancer.