Purpose: In observational studies, higher S-25-hydroxyvitamin D [S-25(OH)D] has been associated with a more favorable cardiometabolic profile in childhood, but results may be confounded. We examined effects of vitamin D supplementation on cardiometabolic outcomes in children and adolescents. 

Methods: We systematically searched relevant databases for randomized controlled trials (RCTs) examining effects of vitamin D supplementation compared to placebo or a lower dose of vitamin D on blood glucose, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), glycated hemoglobin, cholesterol [total, high-density, and low-density lipoprotein (LDL-C)], triglycerides, or blood pressure. We conducted random-effects meta-analyses of weighted mean differences in all participants and in subgroups of overweight/obese versus normal weight participants with or without baseline S-25(OH)D < 50 nmol/L. We also explored associations between responses in S-25(OH)D and outcomes by meta-regression. 

Results: Fourteen RCTs with a total of 1088 participants aged 4–19 years were included. In the meta-analysis, vitamin D supplementation increased S-25(OH)D by 27 nmol/L [95% CI 16; 37] (P < 0.0001) and increased LDL-C by 0.11 mmol/L [0.02; 0.20] (P = 0.02) without any subgroup differences and a generally low to moderate heterogeneity. Vitamin D supplementation had no other effects. However, in the meta-regression analysis, HOMA-IR decreased by 0.51 points [− 0.97; − 0.04] per 10 nmol/L increase in the endpoint S-25(OH)D among overweight/obese participants (P = 0.04). 

Conclusions: These results do not support the use of vitamin D supplementation for improving cardiometabolic health in childhood. Indicated beneficial effects on insulin resistance in those with obesity could be investigated further, while unfavorable effects on LDL-C may be a concern.