Dietary Magnesium Intake in Relation to Plasma Insulin Levels and Risk of Type 2 Diabetes in Women

OBJECTIVE — Higher intake of magnesium appears to improve glucose and insulin ho-meostasis; however, there are sparse prospective data on the association between magnesium intake and incidence of type 2 diabetes. RESEARCH DESIGN AND METHODS — In the Women’s Health Study, a cohort of 39,345 U.S. women aged45 years with no previous history of cardiovascular disease, cancer, or type 2 diabetes completed validated semiquantitative food frequency questionnaires in 1993 and were followed for an average of 6 years. We used Cox proportional hazard models to estimate multivariate relative risks (RRs) of type 2 diabetes across quintiles of magnesium intake com-pared with the lowest quintile. In a sample of 349 apparently healthy women from this study, we measured plasma fasting insulin levels to examine their relation to magnesium intake. RESULTS — During 222,523 person-years of follow-up, we documented 918 confirmed incident cases of type 2 diabetes. There was a significant inverse association between magnesium intake and risk of type 2 diabetes, independent of age and BMI (P 0.007 for trend). After further adjustment for physical activity, alcohol intake, smoking, family history of diabetes, and total calorie intake, the multivariate-adjusted RRs of diabetes from the lowest to highest quintile