Vitamin D and SARS-CoV2 infection, severity and mortality: A systematic review and meta-analysis
What this study found
Vitamin D supplementation was associated with lower COVID-19 severity and mortality, while low baseline vitamin D status was associated with higher infection, severity, and mortality risk. For severity, the pooled association was SRR 0.38 (95% CI 0.20-0.72; 6 studies), and for mortality it was SRR 0.35 (95% CI 0.17-0.70; 8 studies), both indicating reduced risk with supplementation. Low baseline vitamin D was associated with higher infection risk, SRR 2.18 (95% CI 1.55-3.06). The authors concluded that these findings are suggestive but not causal, and that randomized controlled trials are…
- Study & population
- Systematic review and meta-analysis of studies in individuals tested for SARS-CoV-2 or diagnosed with COVID-19, including hospitalized and non-hospitalized populations from multiple regions such as Asia, the United States, and Europe.
- Intervention
- Vitamin D supplementation was evaluated in heterogeneous regimens across included studies, including calcifediol and vitamin D3 (cholecalciferol).
- Key limitation
- The evidence was heterogeneous and relied heavily on observational data, limiting causal inference.
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Open PDFOriginal abstract
To assess the evidence on SARS-CoV2 infection and Covid-19 in relation to deficiency and supplementation of vitamin D, we conducted a systematic review up to April 2021. We summarised data from 38 eligible studies, which presented risk estimates for at least one endpoint, including two RCT and 27 cohort-studies: 205565 patients with information on 25OHD status and 2022 taking vitamin D supplementation with a total of 1197 admitted to the ICU or who needed invasive mechanical ventilation or intubation and hospital stay, and more than 910 Covid-19 deaths. Primary outcomes were severity and mortality and the main aim was to evaluate the association with vitamin D supplementation. Random effects models showed that supplementation was associated with a significant lower risk of both Covid-19 severe disease (SRR 0.38, 95% CI 0.20–0.72, 6 studies) and mortality (SRR 0.35, 95% CI 0.17–0.70, 8 studies). There were no statistically significant dose differences between studies: summary estimates with regular doses remain statistically significant, suggesting that higher doses are not necessary. For patients on vitamin D supplementation, a greater reduction in mortality risk emerged in older individuals and at higher latitudes. Regarding the quality of studies, assessed using the New Castle-Ottawa quality scale, the analysis revealed in most cases no statistically significant differences between low, medium or high quality studies. We found significant associations of vitamin D supplementation with Covid-19, encompassing risks of disease worsening and mortality, especially in seasons characterized by 25OHD deficiency and with not severe patients. Dedicated randomized clinical studies are encouraged to confirm these results.