Vitamin D Supplementation: A Potential Prevention Method against Contagious Viral Respiratory Illnesses

This narrative review explores the protective value of Vitamin D (VD) and its metabolites, such as Vitamin D2 (VD2) and Vitamin D3 (VD3), and their preventive health potentials backed by evidence-based medicine against viral respiratory illnesses (VRI). With the recent events of late 2019, a severe acute respiratory illness began to sweep the globe. This SARS illness was of coronavirus-2 variant known as SARS-CoV-2 (COVID-19). With COVID-19 in mind, the purpose of this paper was to explore a preventative health model utilizing evidence-based medical research to safeguard against similar viral catastrophes. The knowledge gained is essential for the future education of the general population and necessary for a more preemptive and protective approach to VRIs. Google Scholar, PubMed, and DuckDuckgo were the most often utilized internet search engines and databases to collect sources. Twelve evidence-based medical articles were selected based on specific inclusionary and exclusionary criteria. More specifically, eleven systematic-review and meta-analyses (SRMA) and one Randomized Controlled Trial (RCT) were selected. The data extracted from the eleven articles were analyzed to understand the relationship between VD, VD3, and Viral Respiratory illnesses (VRIs). VD is known to have various protective actions on the immune system (IS). First, VD activates gene transcription upon innate immune cells to increase viral defensive proteins such as Defensins and Cathelicidins (Laaski, 2011; Liu, 2006; NIH, 2020). More importantly, VD down-regulates certain specific adaptive immune cells named T helper 2 (Th2). The Th2 cellular pathway indirectly downregulates T helper 1 (Th1), cell pro-inflammatory cytokine storms, thus assisting with viral clearance (Huang, Wang, Li et al., 2020). More EBM research displays an inverse relationship between VD status and VRI, like incidences, severity, and duration of VRIs (Abioye, Bromage & Fawz 2021). Recommendations for future research were presented to understand VD better and its possible use as a potential therapeutic or preventive medicine modality for the public. Proposals on health policy changes within health agencies like the United States Preventative Task Force (USPTF) were also provided. Changes included mandatory health VD screens tables and their metabolites for patients of different ages and breeds to achieve proper VRI protection to prevent future pandemics