COVID-19 and Vitamin D- a Systematic Review.

Introduction: The COVID-19 pandemic has strongly affected global healthcare systems. Prior epidemiological studies on different infectious diseases have shown a strong correlation between serum vitamin D levels and the incidence of certain infectious diseases. Vitamin D has an important immunomodulatory effect on innate immunity and exhibits several other mechanisms in the pathogenesis of the cytokine storm, which is one of the main contributing factors to fatality in COVID-19 patients. Methods: A keyword search was conducted in the PubMed and Google Scholar research databases. The abstracts and/or full texts of selected papers were further evaluated. Articles that fulfilled the inclusion criteria were included in the systematic review. Results: The 28 studies summarized in this review provide observational findings that vitamin D levels are related to the incidence, severity, and mortality rate of COVID-19 infection. The literature does not suggest that COVID-19 could be eliminated with supplementation of vitamin D, but there are implications that vitamin D deficiency might increase the risk for COVID-19 infection and severity of the disease progression. Discussion: Current literature and several guidelines support the supplementation of vitamin D as a reasonable strategy for correcting and preventing vitamin D deficiency. The recommended dose for maintaining normal 25(OH)D levels by consensus is 1000 to 2000 IU vitamin D daily for at-risk teens and adults. Conclusion: Vitamin D supplementation might play an important role in protecting from acute respiratory infections like the SARS CoV2, and in high-risk individuals with COVID 19 from progressing to critical clinical condition and reducing mortality.