A cytokine storm is an excessive release of pro-inflammatory molecules that occurs during severe COVID-19 and is a common cause of death. A new study suggests that vitamin D could reduce the risk of developing a cytokine storm and decrease COVID-19 mortality.

Vitamin D is a fat-soluble vitamin that plays essential roles in numerous physiological processes including the regulation of blood pressure, calcium homeostasis, and immune function. Previous work on other coronaviruses demonstrates that vitamin D can counteract a cytokine storm by strengthening the innate immune response and inhibiting the adaptive immune system from over-responding to a viral infection. COVID-19 mortality varies across countries and age groups, with the elderly being particularly susceptible.

Previous research has suggested a connection between vitamin D deficiency and C-reactive protein (CRP), a protein that increases in the blood in response to inflammation and infection. Furthermore, elevated blood levels of CRP are indicative of severe COVID-19. The current study used large-scale data to investigate whether there is an association between vitamin D deficiency and the severity of COVID-19.

The authors of the study examined COVID-19 data from patients in ten countries, together with vitamin D and CRP data from previous studies. They estimated that patients with normal vitamin D levels had a 15.6 percent reduced risk of severe COVID-19 compared to patients with severe vitamin D deficiency.

These findings suggest that vitamin D could suppress the cytokine storm in COVID-19 patients and reduce disease severity. More research is needed to determine if these findings hold true when vitamin D levels are measured directly.

• Link to the preprint version of the full study.