disproportionately afflicted by COVID-19.
It’s not a complete shock that vitamin D—available by sun, supplement, and diet—could be a factor in COVID-19. It’s been previously found to be protective against respiratory tract infections—many of which are caused by other kinds of coronaviruses than the one that triggered the global pandemic.
Scientists have also identified that people with high vitamin D are more likely to have lower levels of a molecule known as interleukin 6. That’s interesting because doctors trying to control a ferocious and dangerous immune response in COVID-19 patients—known as a cytokine storm—use drugs to target interleukin 6.
While the study’s findings are promising, researchers say they are a long way from knowing how this should translate in day to day life. The study doesn’t prove taking more vitamin D will reduce COVID-19 incidence or transmission. And, as Meltzer says, “We don’t know what the right amount of vitamin D is.”
Taking too much vitamin D can be harmful, with side effects that include kidney damage and heart problems. Meltzer says the safest way to make sure you are getting enough is getting outside (with sunscreen) during the day.
“Putting aside the risks of sunlight—skin cancer, for example—generating vitamin D by sun is probably a sort of safer, more naturally regulated way to do it,” Meltzer said. “But, you also have to be realistic about how practical that is.”
Paradoxically, stay-at-home orders tied to the pandemic may have kept people out of the sun. And as autumn approaches, the chance to catch some rays decreases.
Another paradox: Because vitamin D reduces inflammation, it could reduce symptoms of COVID-19—meaning more infected people who are asymptomatic are silently spreading the virus to others, making it harder to track.
Right now, Meltzer and his team have identified a correlation between vitamin D and COVID-19 incidence. They say that randomized clinical trials are needed to pin down whether vitamin D actually affects risk.
There is one community-based study observing vitamin D supplement levels and COVID-19 contraction in Chicago communities in the works. Another study will observe COVID-19 among health-care workers taking various levels of vitamin D supplements.
Both studies, Meltzer said, are currently recruiting participants and data will not be available for months.
“There are so many areas where vitamin D has been studied, and some of them it seems like it has an effect. Others it doesn’t,” he said. “We often don’t really understand why, but this question of studying Vitamin D just feels to me like one that should have a real level of importance even beyond COVID.”
