Patients from countries with high Covid-19 death rates have lower levels of vitamin D compared to patients in lower-risk countries, according to research from Vadim Backman, professor of biomedical engineering at Northwestern University.
In Covid-19 patients, low vitamin D levels also corresponded with an overreactive immune response known as a cytokine storm. “You don’t die because of what the virus does to the lungs,” Backman says. “The majority of severe cases appear to be caused by cytokine storm.”
Vitamin D can prevent our adaptive immune system from overreacting. This insight may explain why Covid-19 unequally impacts the very young and the very old, even though both have weak immune systems.
“Children don’t really have a mature adaptive immunity. They primarily rely on the innate immune system,” Backman says, “so that’s probably why they don’t have many complications.”
But a review from U.K. health experts cautions that recent studies don’t include clinical trials and don’t provide evidence that vitamin D levels influence the risk of Covid-19 complications.
The National Institutes of Health’s recommended daily allowance is between 400 and 800 international units of vitamin D, depending on age. Mega-dosing can have side effects, Backman says.