New research has found that there may be a link between having a severe vitamin D deficiency and a greater risk of death from COVID-19.
Led by researchers at Northwestern University in the US state of Illinois, the study looked at data on the admission, recovery and mortality rates for patients with COVID-19 at hospitals and clinics in countries with a large number of confirmed patients, including China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the UK and the United States.
As the researchers didn't have data on the patients' vitamin D levels, they took into account the already established link between vitamin D and levels of C-Reactive Protein (CRP), which increase when there's inflammation in your body, and the link between CRP and severe COVID-19 to estimate how vitamin D could potentially affect the severity of COVID-19.
They found that patients from countries with high COVID-19 mortality rates, such as Italy, Spain and the UK, had lower levels of vitamin D compared to patients in countries that were not as severely affected.
More specifically, the researchers found that the risk of severe COVID-19 cases among patients with severe vitamin deficiency is 17.3 percent, and just 14.6 percent for patients with normal vitamin D levels.
Vitamin D prevents our immune systems from becoming dangerously overactive, explained the researchers, and so healthy levels of vitamin D may protect against developing severe complications from COVID-19, including death.
"Our analysis shows that it might be as high as cutting the mortality rate in half," lead researcher Vadim Backman said. "It will not prevent a patient from contracting the virus, but it may reduce complications and prevent death in those who are infected."
However, the researchers stress that this doesn't mean that we should all start taking vitamin D supplements.
"While I think it is important for people to know that vitamin D deficiency might play a role in mortality, we don't need to push vitamin D on everybody," said Backman. "This needs further study, and I hope our work will stimulate interest in this area. The data also may illuminate the mechanism of mortality, which, if proven, could lead to new therapeutic targets."
Backman also added that excessive doses of vitamin D can cause negative side effects, and more research is needed to understand how the vitamin may protect against COVID-19.
"It is hard to say which dose is most beneficial for COVID-19," Backman said. "However, it is clear that vitamin D deficiency is harmful, and it can be easily addressed with appropriate supplementation. This might be another key to helping protect vulnerable populations, such as African-American and elderly patients, who have a prevalence of vitamin D deficiency."
The study has been shared on medRxiv, a preprint server for health sciences, but it has not yet been peer-reviewed, meaning it hasn't been verified by other experts.