Basic characteristics of included literatures.

ObjectivesOur aim was to analyze the results of published randomized controlled trials (RCTs) on vitamin D supplementation for psoriasis in order to explore its effectiveness and safety.Patients and methodsAs of July 7 2023, we conducted a systematic literature search in PubMed, Cochrane, Embase, and Web of Science Core Collection databases. The study outcomes included change values in Psoriasis Area and Severity Index (PASI) (at 3 months, 6 months, and end of follow-up)/Dermatology Life Quality Index (DLQI)/Psoriasis disability index (PDI)/C-reactive protein (CRP), and adverse events.Results333 patients from 4 studies were evaluated. Pooled analyses showed no significant effect of DLQI/PDI/CRP change value (P > 0.05) or PASI change value (3 months, end of follow-up; P > 0.05). Sensitivity analyses and statistical tests did not support the results of the PASI change values (6 months, P = 0.05). However, the results of subgroup analyses should not be ignored(supplementation with vitamin D2 or Asia would be more effective; P = 0.03). There were no serious adverse effects, and only a few individuals experienced nausea.ConclusionsThe efficacy and safety of vitamin D supplementation in the treatment of psoriasis remains unremarkable. The search for a new prognostic index that combines clinical and laboratory factors is needed to compensate for the shortcomings of existing measures and provide stronger evidence of validity.