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Severe Vitamin D deficiency appears to play a significant role in COVID-19 patient outcomes.

Northwestern Medicine researchers including Dr Vadim Backman studied COVID-19 patient data from around the world. They were interested in learning why mortality rates differed from country to country. Searching for a common thread, they saw the light.

 “A common thread seemed to be the levels of Vitamin D, or Vitamin D deficiency across populations,” Backman said. “Those who were Vitamin D deficient seemed to develop higher rate of complications from COVID-19 and also higher rate of mortality.”

Vitamin D has protective benefits. It strengthens and regulates our immune system. But when Vitamin D levels are low, it appears the body is more likely to dangerously overreact to an infection. It’s called a “cytokine storm” – a hyper-inflammatory condition that damages the lungs and other organs and can lead to death. 

“It seems that most patients who die from COVID-19 don’t die necessarily because the virus destroys their lungs,” Backman said. “It’s actually the over-reaction of the immune system trying to respond to the virus, which begins to damage the tissue around the body including the lung. It’s a condition called ARDS, acute respiratory distress syndrome.”

Backman and his team found countries with high COVID-19 mortality rates such as Italy, Spain and the United Kingdom had lower levels of Vitamin D compared to patients in countries that were not as severely affected. The strong correlation means having healthy levels of Vitamin D could protect patients against severe complications, including death from COVID-19.

“Having difference in Vitamin D, between severely deficient levels and normal levels eventually could half the mortality rate in COVID-19 patients,” Backman said.

But don’t overload on supplements, which might have negative side effects.

“I would caution people that the study which we have done, this was based on retrospective data,” Backman said. “It’s not clear what is the dose of Vitamin D that would be therapeutic? We don’t know this yet. But one thing that is clear is that there is absolutely no downside of restoring normal levels of Vitamin D if you are deficient.”

The findings may be particularly beneficial for African Americans and the elderly, groups disproportionately impacted by the virus.

 “More than 50 percent of the elderly are Vitamin D deficient. More than 50 percent of African Americans are vitamin D deficient as well,” Backman said. “So, if we are talking about helping vulnerable groups, this would be one aspect I think would make sense to fix.”

The researchers said their findings need to be confirmed by a formal clinical trial, but they hope the new information will lead to better, perhaps protective treatments for COVID-19.