Effects of Vitamin D Supplements on IL-10 and INFγ Levels in Patients with Multiple Sclerosis: a Systematic Review and Meta-Analysis

Abstract

Background:Vitamin D is one of the considerable environmental factors exhibiting immunomodulatory and anti-inflammatory effects. Objective: To conduct a systematic review and meta-analysis to estimate the effect of vitamin D supplements on IL-10 and INFγ levels in patients with multiple sclerosis. Methods: We searched PubMed, Scopus, EMBASE, CINAHL, Web of Science, Ovid, The Cochrane Library and gray literature, including references of selected studies, conference abstracts which were published up to May 2019. We included single- or double-blinded RCTs or open-label trials in which one of the main outcomes was INFγ and/ or IL-10 levels after vitamin D supplementation. Only articles that had been published in English were included. Results: The literature search yielded 369 articles, that were monitored by us. After eliminating duplicates, 128 studies remained; from these, we excluded observational studies, reviews, case reports and non-randomized trials, and 33 studies remained. Finally, only three articles were included. The mean difference for INFγ was 268.4 and 95 % CI 200.6-336.1. There was no significant heterogeneity (I ² = 0 %, Chi ² = 0.1, p = 0.7). The mean difference for IL-10 was 398.3 and 95% CI -528.05-1324.8). There was significant heterogeneity (I2 = 94 %, Chi2 = 31.1 p < 0.001). Conclusion: The results of this systematic review were not satisfactory. More clinical trials are further needed to evaluate the effects of vitamin D supplements on IL-10 and INFγ levels in patients with multiple sclerosis.