Usual consumption of plant foods containing phytoestrogens and sex hormone levels in postmenopausal women in Wisconsin

Abstract

Consumption of phytoestrogens may reduce hormone‐dependent cancer risk through alterations in the actions or metabolism of steroid hormones. Studies in humans of phytoestrogen‐hormone interactions have been limited and inconsistent. Relations between the consumption of phytoestrogen‐containing foods and serum sex hormones and sex hormone‐binding globulin were studied in a population‐based sample of postmenopausal women who participated in the Nutritional Factors in Eye Disease Study of the Beaver Dam Eye Study. Information on phytoestrogen‐containing foods (broccoli, carrots, cauliflower, chili, dark bread, peas, and dried beans) was collected by interviewer‐administered food‐frequency questionnaires. Estrone, sex hormone‐binding globulin, dehydroepiandrosterone sulfate, and total and free testosterone were measured. Analyses included 246 postmenopausal women not taking hormone replacements. Partial correlations between hormones and intake of phytoestrogen‐containing foods were computed, with adjustment for age, body mass index, years since menopause, and total energy intake. Number of standard servings per week of whole‐grain products from the dark bread group was inversely associated with total testosterone (r = ‐0.20, p = 0.002). Although not statistically significant, other hormones displayed similar inverse associations with dark bread consistent with a common metabolic pathway. Although the magnitude of association was small, the data are consistent with the possibility that consumption of some phytoestrogen‐containing foods may affect levels of testosterone in postmenopausal women.