A research team from Northwestern University conducted a statistical analysis of data gathered from hospitals and clinics across different countries such as China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the United Kingdom and the United States.
Vadim Backman, a professor of Biomedical Engineering at Northwestern University's McCormick School of Engineering and Applied Science, who led the research team, said they were inspired to examine vitamin D levels after noticing unexplained differences in COVID-19 mortality rates from country to country.
According to Backman, while there were some who hypothesized that factors such as differences in healthcare quality, age distributions in population and testing rates might be responsible, their team remained unconvinced.
"None of these factors appears to play a significant role," Backman, who is also the director of Northwestern's Center for Physical Genomics and Engineering, said. He pointed out that Italy’s healthcare system is one of the best in the world, and that differences in mortality rates exist in the same age groups, as well as in countries that have similar testing rates.
It was when the researchers closely looked at data from patients hailing from countries with high COVID-19 mortality rates, namely Italy, Spain and the UK, that they observed a common denominator: they had generally lower levels of vitamin D compared to patients from countries that had significantly lower mortality rates.
In addition, after further examination of the patients’ data, the researchers found a link between low vitamin D levels and "cytokine storms," a hyper-inflammatory condition caused by an overactive immune system. (Related: New research suggests vitamin D may help combat coronavirus.)
“Cytokine storms can severely damage the lungs and lead to acute respiratory distress syndrome and death in patients,” Ali Daneshkhah, a postdoctoral research associate at Northwestern’s McCormick School of Engineering, said in a statement.
According to Daneshkhah, this cytokine storm is what seems to kill a majority of COVID-19 patients, and not the destruction of the lungs by the virus itself, as previously believed.
“It is the complications from the misdirected fire from the immune system,” Daneshkah, the study’s first author, stated.
This is exactly where vitamin D -- an essential nutrient often referred to as the “sunshine vitamin” because it is produced by the body as a response to sun exposure -- plays a major role.
According to Backman, not only does vitamin D enhance the immune system, but it also keeps it from becoming overactive, adding that having healthy levels of vitamin D could protect patients against COVID-19’s more severe complications -- including death.
Despite their findings, the research team does not recommend the immediate hoarding of vitamin D supplements on the market -- not even to those who are at risk of deficiency.
"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," Backman said, noting that the results of their research still need to be studied more thoroughly.
"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 said.
"It is hard to say which dose is most beneficial for COVID-19," he added. "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."
As of this writing, the COVID-19 pandemic has infected over 3.9 million people and killed 270,720 around the world.