Impact of high-dose vitamin D supplementation initiated shortly after diagnosis on residual beta cell function and partial remission rates in children with type 1 diabetes.

Objectives: We aimed to determine the effect of high-dose cholecalciferol supplementation starting soon after diagnosis on residual β-cell function (RBCF) and partial remission (PR) rates in children with type 1 diabetes (T1D).

Methods: A prospective, randomized, open-label study was conducted in children aged 2-12 years with newly-diagnosed T1D. Cases received additional cholecalciferol (60,000 IU every fortnight) for six months, while age-matched controls received standard care. Primary outcome variables included change in RBCF (measured by stimulated C-peptide, SCP) and the proportion of patients with PR (insulin dose-adjusted HbA1c, IDAA1c ≤9.0 %) at study endpoint. Secondary outcomes included change in mean daily insulin dose (DID) and mean HbA1c levels.

Results: The mean serum vitamin D concentrations achieved in cases (n=32, mean age 7.2 ± 2.8 years) were higher at 6 months (44.91 ± 5.36 vs. 24.87 ± 4.10 ng/mL, p<0.001). Compared to controls (n=31, mean age 6.6 ± 2.5 years), children receiving vitamin D exhibited a slower decline in SCP levels (mean decrease -0.28 ± 0.10 vs. -0.50 ± 0.10 ng/mL, p<0.001). The mean decrease in IDAA1c was higher in cases (-11.1 ± 0.56 %) compared to controls (-10.1 ± 0.52 %), but the difference in mean decrease (-1.1 ± 0.61) did not attain statistical significance (p=0.08). At 6 months, PR rates were significantly higher in cases compared to controls (19, 59.4 % vs. 6, 19.4 %, p<0.001). Regression analysis revealed baseline SCP as strong predictor of SCP at the study endpoint (r=0.92, p<0.001).

Conclusions: High-dose vitamin D supplementation may preserve RBCF and prolong PR in children with newly diagnosed T1D. Large-scale randomized controlled trials are warranted.