FRIDAY, Sept. 4, 2020 (HealthDay News) -- There's evidence that low blood levels of the "sunshine vitamin" -- vitamin D -- may increase a person's risk of infection with the new coronavirus, researchers say.
"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," said study lead author Dr. David Meltzer. He's chief of hospital medicine at the University of Chicago Medicine.
For the new study, Meltzer's team tracked coronavirus infections among 489 patients whose vitamin D levels were measured within a year before they were tested for the new coronavirus.
While the study couldn't determine cause and effect, patients with an untreated vitamin D deficiency (blood levels of less than 20 ng/mL) were nearly two times more likely to test positive for the coronavirus than patients with sufficient vitamin D levels, the researchers said.
"Our statistical analysis suggests this may be true for the COVID-19 infection," Meltzer said in a medical center news release.
Half of Americans are deficient in vitamin D, with much higher rates among Black and Hispanic Americans and people who live in areas like Chicago, where it's difficult to get enough sun exposure in winter.
The body produces vitamin D when skin is directly exposed to the sun.
"Understanding whether treating vitamin D deficiency changes COVID-19 risk could be of great importance locally, nationally and globally," Meltzer said. "Vitamin D is inexpensive, generally very safe to take, and can be widely scaled," he noted.
Further research is needed to determine whether vitamin D supplements might reduce the risk of infection with the new coronavirus and even the severity of COVID-19, the study authors said.
Dr. Len Horovitz is a pulmonologist and internist at Lenox Hill Hospital in New York City. Reading over the new findings, he said that research has "suggested that [vitamin] D plays an essential role in the immune system. This current study underscores this: D appears to reduce the risk of being infected with COVID, and other studies have suggested that patients with D deficiency fare worse with COVID."
Horovitz suggested that the pandemic might even be raising levels of vitamin D deficiency.
"Because of city living and especially with 'lockdowns,' there has been less sun exposure and therefore more finding of D deficiency in my practice," he noted.
Luckily, an easy remedy is at hand, since vitamin D supplements are available. "The proper dose depends on patient size and their sunlight exposure, and can be easily measured with a simple blood test," Horovitz said.
Meltzer's group believes there's a need for studies to identify strategies for vitamin D supplementation that may be most effective in specific groups of people. The Chicago researchers said they've already launched several such clinical trials.
The study was published online Sept. 3 in JAMA Network Open.