Prospective Evaluation of the Effect of Short-Term Oral Vitamin D Supplementation on Peripheral Neuropathy in Type 2 Diabetes Mellitus

OBJECTIVE: We aimed to assess the efficacy of short-term oral vitamin D supplementation on peripheral neuropathy in patients with type 2 diabetes. MATERIALS AND METHODS: This prospective, placebo-controlled trial included 112 type 2 diabetic patients with diabetic peripheral neuropathy (DPN) and vitamin D [25(OH)D] deficiency. Patients were sequentially assigned to a treatment group (n = 57) and a placebo group (n = 55). DPN was assessed using a neuropathy symptom score (NSS), a neuropathy disability score (NDS) and a nerve conduction study (NCS). Vitamin D status was determined by measuring the serum total 25(OH)D concentration. Patients received either oral vitamin D(3) capsules or starch capsules once weekly for 8 weeks. The primary outcome was changes in NSS and NDS from baseline. The secondary outcome was changes in the NCS result. RESULTS: Serum 25(OH)D concentrations significantly improved after oral vitamin D supplementation in the treatment group when compared to the placebo group (32.8 ± 23.7 vs. 1.1 ± 3.6, p < 0.0001). Similarly, the improvement in NSS values was significantly greater in the treatment group than in the placebo group (−1.49 ± 1.37 vs. −0.20 ± 0.59, p < 0.001). No improvement was observed for NDS and NCS between the 2 groups after treatment. CONCLUSION: Short-term oral vitamin D(3) supplementation improved vitamin D status and the symptoms of neuropathy in patients with type 2 diabetes.