Researchers from the University of Chicago Medicine have found a link between vitamin D levels and the risk of getting infected with COVID-19, the disease caused by the novel coronavirus.

In a retrospective study of nearly 490 patients tested positive for COVID-19, the researchers measured the vitamin D levels of the patients before testing positive for the coronavirus.

The study, titled “Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results,” was published Thursday in JAMA Network Open.

The team found that the patients who had untreated vitamin D deficiency were twice as likely to test positive for COVID-19 compared to those who had enough vitamin D levels.

Lead author Dr. David Meltzer said, “Vitamin D is important to the function of the immune system and vitamin D supplements have previously been shown to lower the risk of viral respiratory tract infections. Our statistical analysis suggests this may be true for the COVID-19 infection.”

It was also found that nearly half of Americans have vitamin D deficiency, particularly in African Americans, Hispanics, and people living in areas like Chicago where they do not get enough sun exposure in winter.

Dr. Meltzer said, “Understanding whether treating Vitamin D deficiency changes COVID-19 risk could be of great importance locally, nationally, and globally. Vitamin D is inexpensive, generally very safe to take, and can be widely scaled.”

The team emphasized the importance of the findings of the experimental studies to determine whether taking vitamin D supplements can reduce the risk, or potentially severity, of COVID-19.

Dr. Meltzer and his team also highlighted the need for more studies to determine the strategies for vitamin D supplementation, especially in specific populations. The researchers have initiated several human trials at the University of Chicago Medicine and with local partners.