The Benefits of Add-on Therapy of Vitamin D 5000 IU to the Vitamin D Levels and Symptoms in Diabetic Neuropathy Patients: A Randomized Clinical Trial

BACKGROUND: Previous studies have demonstrated a significant relationship between vitamin D deficiency and the development of diabetic peripheral neuropathy (DPN). However, current studies are limited regarding the potential therapeutic benefits of vitamin D therapy in these patients. OBJECTIVE: This study aimed to assess the effect of oral vitamin D supplementation in patients with diabetic peripheral neuropathy in addition to standard treatment. METHODS: This study was a controlled, open-label, randomized clinical trial with an active comparator randomly allocated with a 1:1 ratio. The experimental group received an add-on oral vitamin D 5000 IU once daily and standard treatment (pregabalin, gabapentin, or amitriptyline) over eight weeks. The control group received standard treatment alone. The measured outcomes were the change in the score of the visual analog scale (VAS), numerical rating scale (NRS), and brief pain inventory (BPI). Vitamin D levels were also measured before and after the trial. RESULTS: Data from 68 subjects with DPN was collected and analyzed. Most of them (60.3%) were female, aged 64.96 ± 8.3 years. After eight weeks of treatment, the experimental group showed a more significant reduction of mean VAS (−3.34 ± 2.03 vs −2.37 ± 2.2, p=0.044) and burning pain (1.76 ± 7.16 vs 6.18 ± 13.93, p=0.046) scores compared to controls. Mood also improves better in the experimental group (88.2% vs 70.6%, p=0.031). At the end of the study, vitamin D levels were also improved more significantly in the experimental group (40.02 ± 15.33 ng/mL vs 18.73 ± 6.88 ng/mL; p<0.001) with greater changes from the baseline to week 8 (+24.14±13.68 ng/mL vs +3.10±4.20 ng/mL; p<0.001) compared to control group. The intervention group showed a negative correlation between vitamin D level and VAS score (r = −0.403, P = 0.018). There were no adverse events recorded in this study. CONCLUSION: The addition of oral vitamin D 5000 IU to standard treatment significantly improves pain, mood, and vitamin D levels more effectively than standard treatment alone in patients with diabetic neuropathy. TRIAL REGISTRATION: ClinicalTrials.gov.no NCT04689958.