Research team at Northwestern University finds correlation between vitamin D and covid mortality rates

A research team led by Northwestern University in Evanston found a strong correlation between severe vitamin D deficiency and mortality rates in patients with COVID-19.

Their paper, "The Possible Role of Vitamin D in Suppressing Cytokine Storm and Associated Mortality in COVID-19 Patients" is available at

The paper has not been peer reviewed. The paper’s goal was to “open up dialogue and discussion,” which could lead to studies, said Vadim Backman, who led the research.

But another researcher at the Northwestern University Feinberg School of Medicine and Northwestern Memorial Hospital is waiting for approval to begin a double-blind clinical study on vitamin D and whether it can reduce cytokine storm in patients with COVID-19, according to Benjamin D Keane, Backman’s research assistant.

A separate study by another group of researchers not at Northwestern had similar findings.

The study “The role of Vitamin D in the prevention of Coronavirus disease 2019 infection and mortality,” was published at the beginning of the month in the peer-reviewed journal “Aging Clinical and Experimental Research.”

Another observational study in early April suggested the same thing.

Backman stressed that a correlation between low vitamin D blood levels and mortality rates in patients with COVID-19 does not mean healthy vitamin D levels will have any therapeutic benefit against the virus.

Normal vitamin D levels will also not prevent a person from contracting the virus, but they may reduce the risk of complications and death, he said.

However, people should not start hoarding vitamin D or taking megadoses, Backman said.

“It’s not known what kinds of doses are needed to bring levels back to normal,” Backman said.

In fact, health care experts don't agree on what an optimal blood level of vitamin D actually is.

However, a number of studies regarding vitamin D and the immune system have been conducted by various researchers over the past decade.

Some of these studies have suggested that people with low vitamin D levels are at increased risk of respiratory illnesses, including upper respiratory illnesses, tuberculosis and even asthma and allergies.

Backman said his interest in vitamin D sparked after examining some of the paradoxes surrounding the novel coronavirus.

For instance, Backman noticed a disparity in the mortality rate of European countries. Italy, Spain and the U.K. had higher mortality rates than Germany, he said.

“Germany almost looks like it’s got some different virus,” Backman said. “Its mortality is very different.”

Backman said experts have various theories for these disparities, such as differences in the age of the population, quality of health care, testing methods or the reporting of deaths, Backman said.

Researchers even looked to see if different strains of the SARS-CoV-2 virus might be circulating in different communities.

“But there’s no real evidence of that either,” Backman said.

Another mystery surrounding this virus was the “mortality curve,” he said.

Typically, the people most severely affected by seasonal influenza and other strains of coronaviruses are those with the weakest immune systems: the elderly and the very young, Backman said.

“But young children in general don’t get complications from COVID-19,” Backman said. “They seem to be the safest group of them all. … it’s very different from what you see in other epidemics.”

In addition, people dying from COVID-19 don’t seem to be dying from the virus directly attacking the lungs, but from complications of cytokine storm, a hyperinflammatory state that results from an overreaction of the immune system, he said.

But that, too, could explain why many children don’t develop serious complications from the virus, Backman said.

They rely more on an innate immune system than on a fully developed adaptive immune system, he said.

“They have much less chance of developing a cytokine storm,” Backman said.

While exploring this relationship between vitamin D and COVID-19, researchers conducted a statistical analysis of the average vitamin D levels across different countries: China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the U.K. and the U.S., Backman said.

Researchers also looked at how vitamin D correlated with markers of cytokine storm., Backman said.

And then researchers looked at the data on a more granular level – by regions in each country and by population, Backman said.

They found that countries with higher mortality rates from COVID-19 also had lower levels of vitamin D compared to countries with lower rates, Backman said.

For instance, Backman said, people in northern Italy have, on average, lower vitamin D levels than people in southern Italy.

In London, people who were white generally had higher vitamin D levels than those of, say, South Asian descent, Backman said.

“The elderly are much more likely to be vitamin D deficient,” Backman said.

But vitamin D is at the front line of defense against most infections, including viruses such as COVID-19, Backman said.

“That first line of defense is strong if vitamin D levels are normal,” Backman said.

Backman also is director of Northwestern’s Center for Physical Genomics and Engineering and the associate director for research technology and infrastructure at the Robert H. Lurie Comprehensive Cancer Center at Northwestern University.