Vitamin D supplementation for the treatment of COVID-19: A systematic review and meta-analysis of randomized controlled trials
What this study found
Vitamin D supplementation did not show a statistically significant overall benefit for mortality or other key clinical outcomes in adults with COVID-19. The review noted a non-significant trend toward lower mortality, with the most favorable signal seen for repeated dosing after diagnosis. Across studies, the evidence was low to moderate quality and heterogeneous, so firm conclusions about clinical benefit or optimal dosing could not be made.
- Study & population
- Systematic review and meta-analysis of 8 randomized controlled trials including 657 adults with confirmed COVID-19.
- Intervention
- Vitamin D was evaluated in multiple forms across 8 randomized controlled trials: calcifediol, calcitriol, and cholecalciferol.
- Key limitation
- The evidence base was small and heterogeneous, with different vitamin D forms, doses, timing, and patient settings across only 8 trials.
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Open PDFOriginal abstract
Vitamin D supplementation and its impact on immunoregulation are widely investigated. We aimed to assess the prevention and treatment efficiency of vitamin D supplementation in the context of coronavirus disease 2019 (COVID-19) and any disease-related complications. For this systematic review and meta-analysis, we searched databases (PubMed, Embase, Scopus, Web of Science, The Cochrane Library, medRxiv, Cochrane COVID-19 Study Register, and ClinicalTrial.gov) for studies published between 1 November 2019 and 17 September 2021. We considered randomized trials (RCTs) as potentially eligible when patients were tested for SARS-CoV-2 infection and received vitamin D supplementation versus a placebo or standard-of-care control. A random-effects model was implemented to obtain pooled odds ratios for the effect of vitamin D supplementation on the main outcome of mortality as well as clinical outcomes. We identified a total of 5,733 articles, of which eight RCTs (657 patients) met the eligibility criteria. Although no statistically significant effects were reached, the use of vitamin D supplementation showed a trend for reduced mortality [odds ratio (OR) 0.74, 95% confidence interval (CI) 0.32–1.71, p = 0.48] compared with the control group, with even stronger effects, when vitamin D was administered repeatedly (OR 0.33, 95% CI 0.1–1.14). The mean difference for the length of hospitalization was −0.28 (95% CI −0.60 to 0.04), and the ORs were 0.41 (95% CI 0.15–1.12) and 0.52 (95% CI 0.27–1.02) for ICU admission and mechanical ventilation, respectively. In conclusion, vitamin D supplementation did not improve the clinical outcomes in COVID-19 patients, but trends of beneficial effects were observed. Further investigations are required, especially studies focusing on the daily administration of vitamin D.