The association between vitamin D levels and metabolic syndrome components among metropolitan adolescent population.

Objectives: Vitamin D promotes both lipolysis and lipogenesis, and some pediatric studies showed inconsistent associations between vitamin D and metabolic syndrome (MetS). This cross-sectional study aimed to examine the association between vitamin D levels and MetS components among metropolitan adolescents.

Methods: A total of 4,149 adolescents aged 10-18 years were recruited from 23 metropolises in China. The MetS conditions were assessed according to the International Diabetes Federation consensus definition, and the serum 25-hydroxy vitamin D (25(OH)D) concentrations were analyzed. The association between MetS components and serum 25(OH)D levels was analyzed by the logistic regression model. Restricted cubic spline was applied to the model nonlinear association.

Results: Prevalence of vitamin D deficiency was 74.9%, and 41.2% of study participants had at least one MetS component. After adjustment, the significant trend for a lower waist-to-height ratio was not observed in study participants with higher serum 25(OH)D quartile (p=0.57), but a significant nonlinear association between abdominal obesity and serum 25(OH)D levels was found (p=0.04): the highest risk of abdominal obesity occurred at 14.1 ng/mL of serum 25(OH)D. The association of serum 25(OH)D was significantly inverse with MetS (OR: 0.95; 95% CI: 0.92-0.98), but not with raised triglycerides (OR: 0.99; 95% CI: 0.96-1.01), raised blood pressure (OR: 0.99; 95% CI: 0.97-1.01) and impaired fasting glycemia (OR: 1.03; 95% CI: 1.01-1.04).

Conclusions: The net effect of vitamin D on lipid metabolism may be concentration-dependent, and the actual effect of vitamin D on MetS process may be complex among metropolitan adolescents, though serum 25(OH)D is inversely associated with MetS.