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Study suggests Vitamin D deficiency could raise chances of getting coronavirus

Getting some sunshine increases your vitamin D levels. It's easy now, but it will be harder this winter.
Getting some sunshine increases your vitamin D levels. It's easy now, but it will be harder this winter.Christopher Muther/Globe Staff

University of Chicago Medicine researchers suggest in a new study that there may be a link between vitamin D deficiency and the likelihood of becoming infected with the coronavirus.

“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,” Dr. David Meltzer, chief of hospital medicine at the health system and lead author of the study, said in a statement. “Our statistical analysis suggests this may be true for the COVID-19 infection.”

The observational study looked at 489 patients whose vitamin D level was measured within a year before being tested for COVID-19. Patients who had vitamin D deficiency that was not treated were almost twice as likely to test positive for the coronavirus than patients who had sufficient levels of the vitamin.


The study, published Thursday in the journal JAMA Network Open, suggested that “randomized clinical trials of interventions to reduce vitamin D deficiency are needed to determine if those interventions could reduce COVID-19 incidence.”

There has been interest in the possible effects of vitamin D on susceptibility to the coronavirus since early in the spring, The New York Times reported. Other studies have raised questions about whether the vitamin has any effect on the virus.

A number of clinical trials of Vitamin D are being undertaken, including one about to get underway at Brigham and Women’s Hospital in Boston.

Dr. JoAnn Manson, chief of preventive medicine at the Brigham and a professor at Harvard Medical School, who is leading the study, said Vitamin D “does look promising” but more study is needed.

“I think the key point is that correlation does not prove causation. There are observational studies that strongly support a role of vitamin D in reducing the risk of COVID. However, we don’t yet have randomized clinical trials that prove vitamin D supplementation will reduce the risk of acquiring the infection or having severe disease,” she said. “We need the randomized trials to prove cause and effect.”


She said that in the meantime, people should make sure they are getting enough vitamin D through sunlight, foods, or even supplements, because being deficient is a risk factor for other health problems.

Meltzer and his team have also initiated several clinical trials. “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,” he said in the statement.

Martin finucane can be reached at martin.finucane@globe.com.