Vitamin D: A Potential Mitigation Tool for the Endemic Stage of the COVID-19 Pandemic?

Abstract

The impact of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic and associated development of clinical symptoms of COVID-19 have presented an enormous global impact on our health care systems, public health and economy. To date several observational epidemiological studies consistently found that vitamin D deficiency, measured as low levels of circulating 25-hydroxyvitamin D, is associated with cardiovascular diseases, diabetes, certain cancers, autoimmune diseases and many infectious diseases, including acute respiratory infections. Since vitamin D is not merely immunosuppressive but also acts as an immunomodulator in tolerance and homeostasis, many experts have considered a role of vitamin D in the prevalence and severity of immune mediated inflammatory diseases, such as SARS-CoV-2, adding to the evidence of the importance of vitamin D in the immune response against viral respiratory infections and reinforcing the need for targeted vitamin D supplementation, with a focus on high-risk populations and a high-dose supplementation treatment for COVID-19 hospitalized patients. The expected transition to endemicity of SARS-CoV-2 even further corroborates as a potential of vitamin D as an potential mitigation tool for the prevention of COVID-19. The aim of this paper is to analyse the current evidence regarding vitamin D and present a hypothesis of its potential role in the current COVID-19 pandemic and in the future as a potential preventive measurement in public health.

Keywords: COVID-19; SARS-CoV-2; endemic; immunomodulation; vitamin D; vitamin D deficiency; vitamin D supplementation.

Figure 1

Vitamin D sources, synthesis and metabolism. CYP27B1, cytochrome P450 Family 27 Subfamily B Member 1; CYP24A1, Cytochrome P450 Family 24 Subfamily A Member 1; VD, vitamin D; VDBP, vitamin D binding protein; VDR, vitamin D receptor; VDRE, vitamin D response element; RXR, retinoid-X receptor.

Figure 2

Vitamin D-dependent Immunomodulation. AMP, antimicrobial peptides; APCs, antigen presenting cells; DC, dendritic cells; Th1, type 1 T helper cells; Th17, type 17 T helper cells; Treg, regulatory T cells.

Figure 3

Vitamin D-dependent Protective vs. Hypovitaminosis D-dependent Detrimental Immune Response against SARS-CoV-2. AMPs, antimicrobial peptides; GM-CSF, granulocyte-macrophage colony-stimulating factor; IL-6, IL-8, IL-17A, interleukin 6, 8 and 17A; IFNγ, interferon-gamma; Th1, Th2, Th17, type 1 T helper cells, type 2 T helper cells, type 17 T helper cells; Th; TNFα, tumor necrosis factor alpha.

Figure 4

Authors recommendations regarding vitamin D research and supplementation.

Figure 5

Forecasting the future for the COVID-19 pandemic, including the possible role for vitamin D supplementation.

Figure 6

Summary of key review points.