Vitamin D insufficiency is associated with insulin resistance independently of obesity in primary schoolchildren. The healthy growth study

Objectives: To explore the associations of vitamin D status and obesity with insulin resistance (IR) in children. Methods: A sample of 2282 schoolchildren (9-13 years old) in Greece was examined. Sociode-mographic, anthropometric (weight, height), biochemical (fasting plasma glucose, serum insulin and 25(OH)D), pubertal status and physical activity data were collected, using standard methods. The Vitamin D Standardization Program protocol was applied to standardize serum 25(OH)D values. Results: The prevalence of vitamin D insufficiency (serum 25(OH)D < 50 nmol/L) was higher in obese children compared to their over- and normal-weight counterparts (60.5% vs 51.6% and 51%, P=.017). Furthermore, children with IR (both obese and non-obese) had higher prevalence of vitamin D insufficiency compared to non-obese, non-insulin resistant children (66% and 59.2% vs 49.8%, P<.05), possibly indicating that IR is associated with vitamin D insufficiency, independently of obesity. In line with the above, the results from logistic regression analyses controlled for several potential confounders, showed a 1.48 (95% C.I: 1.2-1.84) higher likelihood for vitamin D insufficiency for insulin resistant children compared to the non-insulin resistant ones, while no significant association was observed with obesity. Conclusions: The present study revealed a high prevalence of vitamin D insufficiency among schoolchildren in Greece, particularly among obese and insulin resistant ones. In addition, it highlighted that the significant association of vitamin D insufficiency with IR is possibly independent of obesity. Further clinical trials are needed to confirm this possible independent association but also explore the potential beneficial effect of vitamin D supplementation on IR and possibly on weight management too.