Effects of Vitamin D Supplementation on COVID-19 Related Outcomes: A Systematic Review and Meta-Analysis
What this study found
Primary prevention: Vitamin D supplementation did not significantly reduce risk of SARS-CoV-2 infection (RR 0.91; 95% CI 0.81–1.02; I2=0). Secondary prevention: insufficient data for hospitalization outcomes; one NRIS reported no significant effect on hospital admission (adjusted OR 1.30; 95% CI 0.51–3.32). Tertiary prevention (hospitalized patients): mortality reduced (RR 0.52; 95% CI 0.36–0.75; I2=54%) and ICU admission reduced (RR 0.35; 95% CI 0.20–0.62; I2=75%). Overall, mortality benefit (RR 0.52; 95% CI 0.36–0.75) was observed in tertiary prevention with some heterogeneity. Subgroup…
- Study & population
- Systematic review and meta-analysis.
- Intervention
- Vitamin D supplementation regimens included oral vitamin D3 (cholecalciferol) and active vitamin D forms (calcitriol, calcifediol), delivered as bolus, daily, or monthly dosing across primary, secondary, and tertiary prevention contexts.
- Key limitation
- High heterogeneity across studies (e.g., ICU mortality I2 up to 82%); reliance on non-randomized studies with risk of bias; wide variation in dosing regimens and populations; incomplete reporting for some outcomes; potential publication bias suggested by funnel plots; results not generalizable to children or younger…
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Open PDFOriginal abstract
The COVID-19 outbreak has rapidly expanded to a global pandemic; however, our knowledge is limited with regards to the protective factors against this infection. The aim of this systematic literature review and meta-analysis was to evaluate the impact of vitamin D supplementation on COVID-19 related outcomes. A systematic search of relevant papers published until January 2022 was conducted to identify randomized controlled trials (RCTs) and non-randomized studies of intervention (NRISs). The primary outcomes included the risk of COVID-19 infection (primary prevention studies on uninfected individuals), hospital admission (secondary prevention studies on mild COVID-19 cases), and ICU admission and mortality rate (tertiary prevention studies on hospitalized COVID-19 patients). We identified five studies (one RCT, four NRISs) on primary prevention, with five (two RCTs, three NRISs) on secondary prevention, and 13 (six RCTs, seven NRISs) on tertiary prevention. Pooled analysis showed no significant effect on the risk of COVID-19 infection. No meta-analysis was possible on hospitalization risk due to paucity of data. Vitamin D supplementation was significantly associated with a reduced risk of ICU admission (RR = 0.35, 95% CI: 0.20, 0.62) and mortality (RR = 0.46, 95% CI: 0.30, 0.70). Vitamin D supplementation had no significant impact on the risk of COVID-19 infection, whereas it showed protective effects against mortality and ICU admission in COVID-19 patients.