Serum and dietary magnesium and the risk for type 2 diabetes mellitus - The atherosclerosis risk in communities study

Background: Experimental studies in animals and cross-sectional studies in humans have suggested that low serum magnesium levels might lead to type 2 diabetes; however, this association has not been examined prospectively. Methods: We assessed the risk for type 2 diabetes associated with low serum magnesium level and low dietary magnesium intake in a cohort of nondiabeti c middle-aged adults (N = 12128) from the Atherosclerosis Risk in Communiti es Study during 6 years of follow-up. Fasting serum magnesium level, catego rized into 6 levels, and dietary magnesium intake, categorized into quartil es, were measured at the baseline examination. Incident type 2 diabetes was defined by self-report of physician diagnosis, use of diabetic medication, fasting glucose level of at least 7.0 mmol/L (126 mg/dL), or nonfasting gl ucose level of at least 11.1 mmol/L (200 mg/dL). Results: Among white participants, a graded inverse relationship between se rum magnesium levels and incident type 2 diabetes was observed. From the hi ghest to the lowest serum magnesium levels, there was an approximate 2-fold increase in incidence rate (11.1, 12.2, 13.6, 12.8, 15.8, and 22.8 per 100 0 person-years; P = .001). This graded association remained significant aft er simultaneous adjustment for potential confounders, including diuretic us e. Compared with individuals with serum magnesium levels of 0.95 mmol/L (1. 90 mEq/L) or greater, the adjusted relative odds of incident type 2 diabete s rose progressively across the following lower magnesium categories: 1.13 (95% CI, 0.79-1.61), 1.20 (95% CI, 0.86-1.68), 1.11 (95% CI, 0.80-1.56), 1. 24 (95% CI, 0.86-1.78), and 1.76 (95% CI, 1.18-2.61) (for trend, P = .01) I n contrast, little or no association was observed in black participants. No association was detected between dietary magnesium intake and the risk for incident type 2 diabetes in black or white participants. Conclusions: Among white participants, low serum magnesium level is a stron g, independent predictor of incident type 2 diabetes. That low dietary magn esium intake does not confer risk for type 2 diabetes implies that compartm entalization and renal handling of magnesium may be important in the relati onship between low serum magnesium levels and the risk for type 2 diabetes.