Vitamin D status and glucose homeostasis in obese children and adolescents living in the tropics.

BACKGROUND: Pediatric obesity continues to rise and has become a major health problem worldwide. Vitamin D deficiency has been increasing among obese non-Asian children and is associated with abnormal glucose homeostasis in obese adults. However, data on the vitamin D status and its association with glucose homeostasis in obese children residing in tropical Asian countries are unavailable.

OBJECTIVE: To assess vitamin D status and glucose homeostasis in obese Thai children.

PATIENTS AND METHODS: A total of 150 obese, and 29 healthy non-obese children and adolescents were enrolled. Weight, height, body mass index (BMI) and waist circumference were obtained. All obese children underwent an oral glucose tolerance test with glucose and insulin measurements. Plasma 25-hydroxyvitamin D (25-OHD) and calciotropic blood chemistries were measured in all participants. Insulin sensitivity indices were calculated from the measured glucose and insulin levels.

RESULTS: Approximately 25% of the obese children and adolescents had impaired glucose tolerance, impaired fasting plasma glucose (FPG) and diabetes. Seventeen out of 150 (11.3%) obese children and 3 out of 29 (10.3%) non-obese children had vitamin D deficiency, which was defined as a 25-OHD level of <50 nmol l(-1). Glucose tolerance and insulin sensitivity indices were comparable between obese children with sufficient vitamin D and those with vitamin D deficiency. There were no relationships among serum 25-OHD; weight, height, and BMI standard deviation scores; insulin sensitivity indices; FPG and insulin; and 2-h plasma glucose and insulin levels.

CONCLUSION: Vitamin D deficiency is not as prevalent in obese Thai children as in obese non-Asian children from high-latitude countries. Adiposity per se is unlikely to be a determinant of vitamin D status in these obese individuals. There was no association between vitamin D deficiency and abnormal glucose homeostasis.