Magnesium Deficiency in Obese Children May Be Linked to Insulin Resistance

Laurie Barclay, MD

May 09, 2005

May 9, 2005 — Magnesium deficiency in obese children is associated with the development of insulin resistance (IR), according to the results of a study published in the May issue of Diabetes Care. The investigators suggest that the deficiency is due to decreased dietary intake. "Magnesium deficiency has been associated with IR and increased risk for type 2 diabetes in adults," write Milagros G. Huerta, MD, from the University of Virginia in Charlottesville, and colleagues. "Obesity and dietary macronutrients clearly play a role in the risk for type 2 diabetes, but the role of micronutrients in this process is not clear. Magnesium is an important cofactor for enzymes involved in carbohydrate metabolism."

The investigators compared 24 obese nondiabetic children (body mass index [BMI] of 85th percentile or greater) with 24 sex- and puberty-matched lean control subjects (BMI <85th percentile) in terms of serum magnesium, indices of insulin sensitivity, dietary magnesium intake based on a food frequency questionnaire, and body composition reflected in air displacement plethysmography.

Mean serum magnesium level was 0.748 ± 0.015 mmol/L in obese children and 0.801 ± 0.012 mmol/L in lean children ( P = .009). Serum magnesium was inversely correlated with fasting insulin (r = –0.36; 95% confidence interval [CI], –0.59 to –0.08; P = .011) and directly correlated with quantitative insulin sensitivity check index (QUICKI) (r = 0.35; 95% CI, 0.06 to 0.58; P = .015).

Mean dietary magnesium intake was 0.12 ± 0.004 mg/kcal in obese children and 0.14 ± 0.004 mg/kcal in lean children ( P = .003). Dietary magnesium intake was inversely correlated with fasting insulin (r = -0.43; 95% CI, -0.64 to -0.16; P = .002) and positively correlated with QUICKI (r = 0.43; 95% CI, 0.16 to 0.64; P = .002).

Lean children consumed more magnesium from green leaf vegetables, fish, beans, yogurt, nuts, and peanut butter than did obese children. Although milk is an important source of magnesium, there were no differences in magnesium intake from milk or total dairy sources between groups.

Study limitations include cross-sectional design, higher proportion of African-American children in the obese group, and lack of measurement of intracellular magnesium.

"The association between magnesium deficiency and IR is present during childhood," the authors write. "Serum magnesium deficiency in obese children may be secondary to decreased dietary magnesium intake.... Further evaluation is required to determine whether increasing dietary consumption of foods with high magnesium content will be a useful approach in improving insulin sensitivity and preventing type 2 diabetes in children."

The University of Virginia General Clinical Research Center, Takeda Pharmaceuticals North America, and the University of Virginia Children's Hospital supported this study. Two of the authors are supported by the National Institutes of Health.

Diabetes Care. 2005;28:1175-1181

Reviewed by Gary D. Vogin, MD

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