Dietary fiber intake and endogenous serum hormone levels in naturally postmenopausal Mexican American women: The multiethnic cohort study

This study investigated dietary fiber intake in association with serum estrogen levels in naturally postmenopausal Latina women with a wide range of fiber intake. Estrone (E-1), estradiol (E-2), and sex-hormone-binding globulin (SHBG) were measured in 242 women. Associations between estrogen levels and intake of dietary fiber, including insoluble and soluble fractions, quantified from a food frequency questionnaire, were examined. The biomarker enterolactone was also measured. After adjustment for age, weight, and other nondietary factors, dietary fiber intake was inversely associated with E, and E2; there was a 22% and 17% decrease (2P(trend) = 0.023 and 0.045) among subjects in the highest quintile of intake compared with the lowest. Fitting dietary fiber together with soluble and insoluble nonstarch polysaccharides (NSP) showed a much greater decrease in E-1 and E-2 (47% and 41%, respectively) while increased soluble NSP intake showed increases in E-1 and E-2 (64% and 69%, respectively). Two foods, avocado and grapefruit, showed significant positive associations with El (2P(trend) = 0.029 and 0.015, respectively). This study suggests that different components of dietary fiber may have very significant different effects on serum estrogen levels. The suggestive findings relating increased estrogen levels to avocado and grapefruit intakes need confirmation.