Introduction: Coronavirus Disease 2019 (COVID-19) pandemic remains a major public health threat in most countries. This article examines epidemiological and clinical observations as well as the link between vitamin D deficiency and covid-19.
Methods: COVID-19 disease is associated with the increased generation of pro-inflammatory cytokines, Creactive protein (CRP), acute respiratory disease syndrome (ARDS), pneumonia, and heart failure. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects pulmonary epithelial cells using the angiotensin converting enzyme-2 (ACE-2) receptor. Besides pulmonary epithelial damage, SARS-CoV-2 also infects macrophages through ACE-2 receptors and activates them. Macrophages, neutrophils, and T cells get activated through sustained elevation of cytokines including interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)alpha, resulting in type 2 pneumocyte apoptosis, and in some patients a path that leads to acute respiratory distress syndrome (ARDS). The host responses are sometimes amplified by an overwhelming expression of pro-inflammatory cytokines. This ‘cytokine storm’ is responsible for some of the serious manifestations of COVID-19 such as ARDS. Hypoxemia and bilateral lung infiltration are features reminiscent of severe viral pneumonia that result from endothelial injury, excessive cytokines, and immune overkill. Low levels of vitamin D can increase the likelihood of developing multiple acute and chronic ailments including cardiovascular and autoimmune diseases, diabetes, cancer, infectious diseases, dental caries (DC). Many retrospective studies have found an association between vitamin D levels and COVID-19 severity and mortality. In clinical studies, low levels of serum vitamin D were associated with acute respiratory tract infections including epidemic influenza.
Results: Studies in the pediatric population demonstrated that patients with COVID-19 had significantly lower vitamin D levels compared with controls. In addition, fever was significantly higher in patients who had deficient vitamin D levels compared with patients who had sufficient levels. Additionally, older adults with vitamin D deficiency and COVID-19 had worse morbidity outcomes compared with those who were not vitamin D deficient. A prospective, interventional study found that a high dose of calcifediol reduced the need for intensive care stays in patients infected with COVID-19. A few studies have also reported on a significant association between sun exposure, vitamin D, and susceptibility to and recovery from COVID-19.
Conclusion: Perhaps the most important finding was that vitamin D deficiency increased the risk of developing COVID-19 by a factor of 5 after adjusting for age. Prospective interventional studies are required to validate the hypothesis that vitamin D supplementation can be helpful for the prevention and treatment of COVID-19.
Keywords: COVID-19; acute respiratory disease syndrome (ARDS); vitamin D