OBJECTIVE: Many treatment modalities have been used to manage psoriasis; however, there is, to our knowledge, no pooled estimate for the effectiveness of oral vitamin D supplements in patients with psoriasis. Hence, the aim of the present study was to systematically review and meta-analyze the efficacy of oral vitamin D supplementation in improving disease severity of patients with psoriasis.METHODS: A systematic literature review was performed on the electronic databases PubMed, Embase, and Cochrane Central and the gray literature for retrieving randomized controlled trials comparing oral vitamin D supplementation with placebo. The primary outcome was the change of Psoriasis Area and Severity Index (PASI) score. We used the random effects model for synthesizing the evidence.RESULTS: Of the total 5018 search results, 4 studies were included in the qualitative and 3 studies in quantitative analysis. Vitamin D supplementation was effective in ameliorating the PASI score after 6 mo of intervention (mean difference [MD] = -0.92, 95% confidence interval [CI] = -1.72 to -0.11). However, after the Hartung-Knapp adjustment, the results became non-significant (MD = -0.92, 95% CI = -2.21 to 0.38).CONCLUSIONS: A favorable effect of oral vitamin D supplementation in patients with psoriasis could not be verified. More randomized controlled trials with larger sample sizes are needed to produce robust results.