An interesting question which will require additional research is whether vitamin D may play a role in COVID-19. Vitamin D is known to be essential to immune function. Some initial research suggests that vitamin D may reduce COVID-19 severity by suppressing the cytokine storm in COVID-19 patients. Vitamin D deficiency is more common among persons with naturally dark skin. The pigment (melanin) in dark skin doesn’t absorb as much UV radiation, which stimulates natural skin production of vitamin D. This may contribute to an explanation for why African-American and Latinos in the US are more likely to become infected with SARS-CoV2 and experience more severe COVID-19, including being more likely to die from the disease.
A recent study of 14,000 members of an Israeli HMO who were tested for SARS-CoV2 infection from February 1st to April 30th, 2020, and who had at least one previous blood test for plasma vitamin D levels found that low plasma vitamin D levels were associated with an increased likelihood of COVID-19 infection and of hospitalization due to COVID-19.
Undoubtedly more research will continue to shed light (excuse the pun) on this topic.