Effect of Vitamin D Supplementation on Fatigue in Multiple Sclerosis: A Systematic Review and Meta-Analysis

Vitamin D supplementation has been considered a possible treatment to reduce the risk of disease activity and progression in people with multiple sclerosis (MS). However, its effect on disease symptoms remains unclear. The aim of this meta-analysis was to conduct a systematic review to assess the effect of vitamin D on fatigue in this population. The systematic review was conducted using the MEDLINE, Cochrane Library, Embase and Web of Science databases from inception to May 2023. Randomized controlled trials (RCTs) reporting pre-post changes in fatigue after vitamin D supplementation were included. Pooled effect sizes and 95% confidence intervals (95% CIs) were calculated by applying a random effects model with Stata/SE (Version 16.0; StataCorp., College Station, TX, USA). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. A total of five studies with 345 individuals (271 females; age range: 25.4-41.1 years) were included. A significant reduction in fatigue was perceived when vitamin D supplementation was compared with a control group: -0.18 (95% CI: -0.36 to -0.01; I² = 0%). Thus, our findings show that the therapeutic use of vitamin D on fatigue in people with MS could be considered. Nevertheless, due to the lack of agreement on the dose to be applied, it is recommended to use it under medical prescription.