Is there a role for vitamin D in the treatment of COVID-19?

As we continue to deal with the COVID-19 pandemic causing spiking numbers of cases, the scientific and medical communities continue to search for effective treatments and preventive measures. We have clearly established the importance of wearing masks, physical distancing, and frequent handwashing.

As of this article’s writing, there are over two hundred fifty articles on PubMed about the connection between vitamin D and COVID-19. As the research studies are undergoing, evidence is mounting that adequate vitamin D levels may be a protective factor against COVID-19 infection and severity. Here’s what the research shows.

Vitamin D can help fight infections

Vitamin D has long been shown to reduce the risk of viral infections through mechanisms that lower viral replication rates and reduce inflammatory damage to the lungs’ lining. Although causality has not been established, vitamin D deficiency is associated with increased susceptibility to infectious diseases, including acute upper respiratory infections. Studies have shown an inverse relationship between vitamin D levels with severity of respiratory viral infections.

Regarding the SARS-CoV-2 virus, vitamin D may help twofold by supporting the production of antimicrobial peptides that reduce the likelihood of infection with the virus and reduce the inflammatory response to infection with SARS-CoV-2 which can cause lung injury and result in poorer outcome from the infection.

There is evidence that vitamin D may specifically help people with COVID-19

Several correlations have been identified that suggest that vitamin D status may affect COVID-19 infection and severity. For example, SARS-CoV-2 started its spread in the northern hemisphere at the end of 2019 when vitamin D levels were at their lowest. Nations in the northern hemisphere have higher case numbers and mortality. An analysis across Europe found that COVID-19 mortality was significantly associated with vitamin D status.

Another significant correlation involves affected populations. Black and minority ethnic people, populations that are more likely to have vitamin D deficiency, are showing worse outcomes than white people by COVID 19. This may at least in part explain the black-white disparity in adverse COVID-19 outcomes. Vitamin D deficiency is also commonly reported in the same populations that have worsening outcomes of COVID-19 which include older age, male sex, obesity, and those with certain chronic diseases such as diabetes mellitus and coronary artery disease. A review by Teymoori-Rad and Marashi states, “There are growing data indicating that vitamin D supplementation could potentially be effective in treatment and prevention of COVID‐19.”

Vitamin D supplementation is safe

Vitamin D deficiency is common and supplementation is a safe intervention. Recent results from a large meta-analysis failed to find any evidence that vitamin D caused healthy people’s adverse effects. In a short abstract, Bergman recommends that when possible, providers should test vitamin D levels and supplement those below 50 nmol/L (20 ng/mL).

We are now entering the time of year in the northern hemisphere when vitamin D levels are at their lowest due to decreased sun exposure. Moreover, the pandemic has increased need for containment at home, exacerbated by cold weather forcing more indoor time, which will further limit sunlight exposure. Therefore, now is a critical time to revisit the importance of adequate vitamin D levels.

Given that vitamin D deficiency is common, that populations with vitamin D deficiency correlate with those at increased risk for more severe COVID-19 infection, and that studies are increasingly indicating a possible role in the treatment, shouldn’t we at least ensure that those who are deficient receive adequate vitamin D supplementation to obtain sufficient levels?

Teresa Fuller is a pediatrician.