Relation of Dietary Carbohydrates Intake to Circulating Sex Hormone-binding Globulin Levels in Postmenopausal Women

Background Low circulating levels of sex hormone-binding globulin (SHBG) have been shown to be a direct and strong risk factor for type 2 diabetes, cardiovascular diseases, and hormone-dependent cancers, although the relation between various aspects of dietary carbohydrates and SHBG levels remains unexplored in population studies. Methods Among postmenopausal women with available SHBG measurements at baseline (n = 11,159) in the Women's Health Initiative, we conducted a comprehensive assessment of total dietary carbohydrates, glycemic load (GL), glycemic index (GI), fiber, sugar, and various carbohydrate-abundant foods in relation to circulating SHBG using multiple linear regressions adjusting for potential covariates. Linear trend was tested across quartiles of dietary variables. We used Benjamini and Hochberg's procedure in calculating the false discovery rate (FDR) for multiple comparisons. Results Higher dietary GL based on total and available carbohydrates, dietary GI based on total and available carbohydrates, and higher intake of sugar and sugar sweetened beverages were associated with lower concentrations of circulating SHBG (all Ptrend < 0.05; q-value after FDR correction = 0.04, 0.01, 0.07, 0.10, 0.01, <.0001, respectively). In contrast, women with greater intake of dietary fiber tended to have elevated SHBG levels (Ptrend = 0.01, q-value after FDR correction = 0.04). There was no significant association of total carbohydrates or other carbohydrate-abundant foods with SHBG concentrations. Conclusions These findings suggest that low GL/GI diets with low sugar and high fiber content may be associated with higher serum SHBG concentrations among postmenopausal women. Future studies investigating whether lower GL/GI diets increase SHBG concentrations are warranted.