Sept. 3 (UPI) -- Vitamin D deficiency increases a person's risk for catching COVID-19 by 77% compared to those with sufficient levels of the nutrient, a study published Thursday by JAMA Network Open found.
As many as one in four of the nearly 500 participants in the study were found to have less-than-optimal levels of vitamin D, the data showed.
Among those found to be lacking the key nutrient, 22% contracted COVID-19, the data showed.
Of the 60% of study subjects with adequate vitamin D levels, just 12% were infected, according to the researchers.
"There is prior evidence from multiple sources that vitamin D can enhance both innate and adaptive immunity," Dr. David O. Meltzer, a professor of medicine at the University of Chicago, told UPI.
Innate immunity refers to the body's natural immune system response. Adaptive immunity describes how the immune system adjusts to a new pathogen -- like a virus -- that is able to evade its natural response.
"Vitamin D also ... may prevent the excess inflammation that is part of the challenge in managing severe COVID-19," Meltzer said.
Based on existing research, many physicians recommend that patients take vitamin D supplements if their diet is lacking in the nutrient because it has been shown to play a role in immune health, according to Kathryn A. Boling, a family physician at Mercy Medical Center in Baltimore, who was not part of the JAMA Network Open study.
"There are some dietary sources of vitamin D, including fatty fishes such as salmon, eggs, mushrooms and fortified foods, including most milk and dairy products, but it is not easy to get the levels one would get from supplements from these dietary sources alone," Meltzer said.
"Regular exposure to sunlight can [also] raise vitamin D levels," he said.
For this study, Meltzer and his colleagues analyzed data on 489 University of Chicago Medicine patients for whom vitamin D status was included in their electronic health records before the start of the COVID-19 outbreak in the United States.
Researchers then tracked the health of these patients from March 3 to April 10.
Of the 489 patients, 124, or 25%, had insufficient vitamin D levels in their blood, while 287, or 59%, were found to have sufficient levels of the nutrient, the data showed.
The vitamin D status of the remaining 16% of participants was "uncertain," according to the researchers.
Vitamin D deficiency was found to increase the risk for testing positive for COVID-19 by 77%, while older age -- which has been linked with higher risk for the disease -- only raised the likelihood by 6%, the study showed.
Non-White study participants were 2.5 times more likely to test positive for the virus, the researchers found.
"Vitamin D deficiency was associated with an increased likelihood of testing positive for COVID-19," Meltzer said. "Given that vitamin D deficiency is common, supplementation of vitamin D intake might reduce the likelihood of developing COVID-19."