The effect of hypovitaminosis D normalization on diabetic neuropathy

Abstract

Background Few data on the association between vitamin D levels and peripheral nerve function are available from human studies, although diabetic peripheral neuropathy (DPN) is a common complication of diabetes mellitus. Unfortunately, pharmacological treatment is often partially effective or accompanied by unacceptable side effects, and a new concept for the management of DPN is imperative. The purpose of this study was to clarify the impact of hypovitaminosis D correction on DPN in type 2 diabetic (DM2) patients. Materials and methods Fifty patients with a mean age of 54.72 ± 9.00 years with DM2 (disease duration 14.62 ± 5.95 years) were recruited. They were assessed clinically for neuropathy using the Michigan Neuropathy Screening Instrument, the Toronto Clinical Score System, and nerve conduction study (NCS) of the sural, popliteal, and ulnar nerves. At same sitting, vitamin D was assessed by measuring 25-dihydroxy, and then repeat Toronto Clinical Score System and NCS were carried out after vitamin D correction. Results Neuropathy severity was significantly improved after vitamin D supplementation. The mean ± SD neuropathy severity was 11.60 ± 2.90 before treatment and 10.82 ± 3.31 after treatment. Moreover, there was improvement of NCS in mild DPN after vitamin D correction but failed to show the same effect in moderate and severe cases. Conclusion Normalization of low vitamin D level has a potential beneficial effect in reducing neuropathy severity in DM2, and hence serum 25-hydroxyvitamin D level should be tested and low levels should be corrected to improve neuropathy symptoms. Further studies in a larger scale are required to confirm these results and re-evaluate patients with severe and moderate DPN.