Prevalence of vitamin D insufficiency in obese children and adolescents

Objective: Recent studies have shown a broad prevalence of vitamin D deficiency in adults. Serum 25-hydroxyvitamin D (25-OHD) levels were reported to be inversely related to body mass index (BMI) and body fat content and correlated directly with hypertension, degree of insulin resistance and progression to diabetes mellitus. We sought to determine the prevalence of vitamin D insufficiency and markers of metabolic syndrome in an obese pediatric population. Methods: Charts of 217 obese (weight > 95(th) percentile for age and sex) children (118 females, 99 males; mean BMI 32.2 +/- 6.4 kg/m(2); mean age 12.9 +/- 5.5; age range 7-18 years) who had received a standard physical examination at the pediatric endocrine clinic of the Infants and Children's Hospital of Brooklyn at Maimonides, Brooklyn, NY, were retrospectively analyzed. Data obtained included age, sex, weight, BMI, height and systolic and diastolic blood pressure. The routine bloodwork panel for obesity at our pediatric endocrine facility includes fasting 25-OHD, total cholesterol, high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), triglycerides, ALT, AST, thyroid stimulating hormone (TSH), total T-4, and insulin and glucose. Insulin sensitivity as calculated by quantitative insulin-sensitivity check index (QUICKI = 1/[log(I-0) + log(Go)], where 10 is fasting insulin and Go is fasting glucose) was computed following the visit. Results: Overall, 55.2% of patients were vitamin D insufficient (25-OHD < 20 ng/ml). Severely low vitamin D levels (25-OHD ! 10 ng/ml) were seen in 21.6% of 217 patients, which represents almost half of the insufficient group. In the 25-OHD < 20 ng/ml group age, BMI, and SBP were significantly higher than in the 25-OHD >= 20 ng/ml group, while QUICKI (< 0.35 is consistent with insulin resistance) was borderline low in the < 20 ng/ml group. HDL-C was significantly lower in the 25-OHD <= 10 ng/ml group. The 25-OHD levels correlated negatively with BMI and positively with HDL-C. No other findings were significant. Conclusion: More than half of the obese children had vitamin D levels < 20 ng/ml with equal gender distribution. Vitamin D insufficiency was associated with increased age, BMI, and SBP, and decreased HDL-C.