Vitamin D supplementation in individuals with type 1 diabetes mellitus (T1DM): a systematic review and meta-analysis focusing on pediatrics.

BACKGROUNDS: Type 1 diabetes mellitus (T1DM) is a significant global health concern, particularly among pediatric populations. Emerging evidence suggests that vitamin D supplementation may support glycemic control in individuals with T1DM; however, existing findings are inconsistent, underscoring the need for further investigation.

METHODS

A comprehensive search of PubMed, Scopus, Cochrane Central, and Web of Science was conducted up to January 2024 to identify relevant English-language randomized controlled trials (RCTs). Risk of bias (ROB) was assessed using the ROB-2 tool. A random-effects model was employed for the meta-analysis using Stata version 17.

RESULTS

From 2,744 records screened, twelve RCTs including 485 participants with T1DM were included. Vitamin D supplementation did not significantly impact HbA1c levels (-1.60 [-3.78, 0.57]; I² = 98.07%) but was associated with significant reductions in C-peptide levels (-2.54 [-4.97, -0.11]; I² = 97.03%), fasting blood sugar (FBS) (-1.44 [-2.67, -0.22]; I² = 91.10%), and daily insulin requirements (-0.44 [-0.82, -0.06]; I² = 58.64%). Moreover, 25(OH)D concentrations significantly increased following supplementation (4.19 [3.26, 5.13]; I² = 82.85%). No serious adverse events were reported, supporting the safety of supplementation.

CONCLUSION

Vitamin D supplementation showed potential benefits in reducing insulin requirements and fasting blood glucose in pediatric T1DM populations. However, its effect on HbA1c remains inconclusive, and the observed reduction in C-peptide levels requires cautious interpretation due to high heterogeneity and possible confounding factors. The certainty of evidence for all outcomes was rated as “low” to “very low” per GRADE assessment. Further large-scale, long-term RCTs are warranted.