Review the Research
Get summaries of key research on vitamin D and COVID-19
Prognostic and Therapeutic Role of Vitamin D in COVID-19: Systematic Review and Meta-Analysis
Take Home Message
This meta-analysis found vitamin D deficiency/insufficiency increased susceptibility to COVID-19 and severe COVID-19, however there was a high risk of bias and heterogeneity.
Results
- 76 studies satisfying eligibility criteria were included. Seventy-two observational studies were included in the meta-analysis.
- Vitamin D deficiency/insufficiency increased the odds of developing COVID-19, severe disease and death.
- 25-hydroxy vitamin D (25(OH)D) concentrations were lower in individuals with COVID-19 compared to controls, in patients with severe COVID-19 compared to controls with non-severe COVID-19, and in non-survivors compared to survivors.
- The association between vitamin D deficiency/insufficiency and death was insignificant when studies with high risk of bias or studies reporting unadjusted effect estimates were excluded. Risk of bias and heterogeneity were high across all analyses.
- Discrepancies in timing of vitamin D testing, definitions of severe COVID-19 and vitamin D deficiency/insufficiency partly explained the heterogeneity.

Who
76 observational studies including almost 2 million adults.
Things to Keep in Mind
The authors point out that risk of bias was very high in all studies and that the main source was the timing of vitamin D testing in relation to onset of COVID-19 which makes it difficult to determine if the vitamin D levels were a result of the illness itself.
Author’s Conclusions
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Multiple observational studies involving nearly two million adults suggest vitamin D deficiency/insufficiency increases susceptibility to COVID-19 and severe COVID-19, although with a high risk of bias and heterogeneity. Association with mortality was less robust. Heterogeneity in RCTs precluded their meta-analysis.
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Study Design
- A systematic review and meta-analysis was conducted to determine the association between vitamin D deficiency/insufficiency and susceptibility to COVID-19, its severity, mortality and role of vitamin D in its treatment.
- CINHAL, Cochrane library, EMBASE, PubMED, Scopus, and Web of Science were searched up to 30.05.2021 for observational studies on association between vitamin D deficiency/insufficiency and susceptibility to COVID-19, severe disease and death among adults, and, randomized controlled trials (RCTs) comparing vitamin D treatment against standard care or placebo, in improving severity or mortality among adults with COVID-19.
Reference
Dissanayake HA, de Silva NL, Sumanatilleke M, de Silva SDN, Gamage KKK, Dematapitiya C, Kuruppu DC, Ranasinghe P, Pathmanathan S, Katulanda P. Prognostic and Therapeutic Role of Vitamin D in COVID-19: Systematic Review and Meta-analysis. J Clin Endocrinol Metab. 2022 Apr 19;107(5):1484-1502. doi: 10.1210/clinem/dgab892. PMID: 34894254; PMCID: PMC8689831.