Does vitamin D level have effect on COVID-19 outcomes?

The severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), a type of coronavirus that causes the condition known as coronavirus disease, was first reported in Wuhan, China in 2019. It commonly affects the respiratory system and is known to produce, in some cases, pneumonia like symptoms, and even death. However, 25 hydroxyvitamin D commonly known as vitamin D, is, when in its hormonal form, involved in many processes throughout the body, including bone health and immune function. Several studies have linked vitamin D to increased resistance to infection, but the link between vitamin D levels and COVID-19 infection, severity and mortality is yet to be fully ascertained. Several studies have linked vitamin D serum levels and deficiency to differing levels of COVID-19 outcome. This review seeks to investigate these claims made in these studies to help add to the body of knowledge and come to a greater understanding of the link between vitamin D and COVID-19 infection.