The impact of vitamin D administration on mortality in COVID-19 patients: a systematic review and meta-analysis of randomized controlled trials

Introduction: Vitamin D, known for its role in bone health, is now being explored for its immunomodulatory effects. This study aimed to evaluate the impact of vitamin D supplementation on mortality in coronavirus disease 2019 (COVID-19) patients through a systematic review and meta-analysis of randomized controlled trials. Methods: A comprehensive search was conducted across PubMed, Scopus, Web of Science, and preprint servers for eligible trials up to July 8, 2024. Two investigators independently screened the records and assessed the risk of bias using the Cochrane Risk of Bias Tool. Trials were eligible if they compared vitamin D with control interventions in adults with COVID-19. Data extraction and analysis were carried out independently, employing a random-effects model to estimate pooled odds ratios for mortality. Results: Nineteen randomized controlled trials with 2495 participants were included. The meta-analysis showed a significant reduction in all-cause mortality with vitamin D supplementation (pooled OR 0.72, 95% CI 0.53–0.98; I² = 20%). Subgroup analysis for severe COVID-19 cases also indicated significant mortality reduction (pooled OR 0.57, 95% CI 0.35–0.92; I² = 18%). Conclusion: Vitamin D supplementation appears to reduce mortality in COVID-19 patients, especially in severe cases. These findings highlight the potential benefits of vitamin D as an adjunct treatment in COVID-19, though further large-scale trials are needed to confirm these effects and determine optimal dosing.