Low dietary magnesium is associated with insulin resistance in a sample of young, nondiabetic black Americans

In both humans and experimental animals, dietary induced magnesium deficiency is correlated with insulin resistance. The purpose of this study was to determine whether dietary magnesium intake is associated with insulin sensitivity or blood pressure in a sample of nondiabetic, young adult black Americans. We also examined dietary calcium, potassium, and sodium intake. The study was conducted on a sample (n = 179) of young adults aged 30 +/- 3.4 years who had been followed longitudinally. Nutrient intake was assessed by obtaining a 24-h recall interview of dietary intake. Intake data were entered in a nutrient analysis program (Nutritionist III), which quantitated micronutrients, macronutrients, and minerals. We classified the sample into insulin-sensitive (IS) and insulin-resistant (IR) groups, according to insulin-stimulated glucose use (M) measured during insulin clamp. M correlated positively with magnesium intake in mg/kg of fat-free mass (r = 0.15, P < .05 overall; in men, r = 0.25, P < .02). There was a significant negative correlation of total dietary magnesium intake with the sum of insulin levels measured during an oral glucose tolerance test (OGTT) (r = -0.13, P < .05). When corrected for body fat, in men there was also a significant correlation of dietary magnesium intake, measured in mg/kg of fat-free mass, with the sum of insulin concentrations on the OGTT (r = -0.22, P < .05). When cases were categorically classified as IS versus IR, magnesium intake in mg/kg of fat-free mass was lower in IR (2.97 +/- 1.4) than in IS (3.68 +/- 2.2; P = .022). These results suggest a possible role for dietary magnesium in insulin resistance. (C) 1999 American Journal of Hypertension, Ltd.