The short-term effect of high dose vitamin D3 supplementation in improving Hypovitaminosis in patients with type 2 diabetes - A randomized clinical trial

Background: Type 2 diabetes (T2D) is an epidemic public health concern with considerable morbidity and mortality. Previous research has shown the association between T2D and vitamin D deficiency. This vitamin significantly affects insulin function, which plays a critical role in T2D development. Aims: A prospective double-blinded randomized controlled trial was conducted to test the hypothesis that vitamin D3 (VD3) supplementation can correct VD deficiency without the risk of hypervitaminosis. Methods: The participants of this study included 62 patients with T2D and hypovitaminosis D3. Of these patients, 30 received cholecalciferol (50,000 IU weekly for 8 weeks), and 32 received identical placebo tablets for 8 weeks. Before and after the intervention, patients were subjected to VD3 level assessment through fasting blood samples. Results: After 8 weeks of intervention, the mean changes in serum VD3 levels in the VD3 group were significant compared to the placebo group (i.e., 21.9 ± 10 vs. 1.2 ± 7 ng/ml, P < 0.001). Also, comparing serum D3 levels of the endpoint with the baseline revealed statistically significant changes in the VD3 group (40 ± 10 vs. 18.1 ± 6 ng/ml, P < 0.001) but no significant change in the placebo group (18.9 ± 7 vs. 20.1 ± 7, P = 0.37). Conclusion: The results showed that administering a weekly dose of VD3 supplement could improve serum levels above 30 ng/ml in patients with T2D and compensate for vitamin deficiency without the risk of hypervitaminosis, which occurs at the levels above 100 ng/ml of 25(OH)D. However, further large-scale studies are needed to determine if these findings are applicable.