A cross-sectional study of vitamin D and insulin resistance in children.

OBJECTIVE Vitamin D deficiency is common and has been associated with several non-bone/calcium related outcomes. The objective was to determine the association between serum 25-hydroxyvitamin D (25-OH-D) and fasting glucose, insulin and insulin sensitivity in obese and non-obese children. PATIENTS/SETTING/DESIGN: Cross-sectional study of 85 children aged 4-18 years recruited from the local Philadelphia community and Sleep Center. MAIN OUTCOME MEASURES Fasting blood glucose, insulin and 25-OH-D were measured. Insulin resistance was calculated using homeostasis model assessment (HOMA). Body mass index standard deviation scores (BMI-Z) and pubertal stage were determined. Multivariable linear regression was used to determine factors associated with decreased 25-OH-D and to determine the association of vitamin D with HOMA. RESULTS Median 25-OH-D was 52 nmol/l (IQR 34-76). 26% of subjects were vitamin D sufficient (25-OH-D ≥75 nmol/l), 27% had intermediate values (50-75 nmol/l) and 47% were insufficient (25-50 nmol/l) or frankly deficient (<25 nmol/l). In the multivariable model, older age, higher BMI-Z and African-American race were all negatively associated with 25-OH-D; summer was positively associated with 25-OH-D. Lower 25-OH-D was associated with higher fasting blood glucose, insulin and HOMA after adjustment for puberty and BMI-Z. CONCLUSION Low 25-OH-D, common in the paediatric population at risk for diabetes (older children, African-Americans, children with increasing BMI-Z) is associated with worse insulin resistance.