Share on Pinterest
Experts say vitamin D can help bolster the immune system, allowing it to better combat illnesses such as COVID-19. Getty Images
  • New studies conclude that vitamin D can reduce your risk of developing COVID-19 as well as decrease the severity of the illness.
  • Experts say vitamin D boosts the immune system, which can help fight off ailments such as COVID-19.
  • The best way to get vitamin D is through sunshine and healthy meals, but supplements can also be used.

Vitamin D is a well-known immune booster.

Now, a series of recently published studies say the supplement can also protect you from contracting SARS-CoV-2, the virus that can cause COVID-19. And vitamin D may reduce the severity of illness if you do test positive for COVID-19.

In one study, University of Chicago Medicine researchers led by Dr, David Meltzer, the university’s chief of hospital medicine, found a relationship between vitamin D deficiency and risk of developing COVID-19.

The researchers studied 489 patients at the hospital and observed that those with a vitamin D deficiency (defined as less than 20 nanograms per milliliter of blood) were almost twice as likely (1.77 times higher) to test positive for the novel coronavirus than those with normal levels of vitamin D.

“These findings appear to support a role of vitamin D status in COVID-19 risk,” the researchers wrote in their retrospective cohort study.

They also called for further clinical studies on the possible link between the vitamin and the disease.

Meltzer told Healthline that he ranked getting adequate vitamin D in the diet “below masks and hygiene” in terms of COVID-19 prevention, but, “I think it should be near the top of everyone’s list.”

“There’s a lot of evidence that we should be taking [vitamin D deficiency] very seriously,” Meltzer said. “If you’re taking a reasonable dose of vitamin D, it’s hard to see how it hurts and it could help a lot.”

“If you’re deficient in vitamin D that does have an impact on your susceptibility to infection,” agreed Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, in a recent Instagram Live interview with actress Jennifer Garner. “I would not mind recommending and I do it myself, taking vitamin D supplements.”

More than 40 percent of the U.S. population is deficient in vitamin D, which can be found in food like salmon and other fatty fish, egg yolks, mushrooms, and foods fortified with the vitamin, such as milk.

Vitamin D requires exposure to sunlight to activate in the body, a unique characteristic of vitamins.

A recent meta-analysis of 40 research studies found that daily, long-term doses of vitamin D seemed to protect against acute respiratory infections. Other studies also have found associations between vitamin D levels and COVID-19 susceptibility.

Notably, a small randomized study from the University of Grenada in Spain found that of 50 people with COVID-19 treated with calcifediol, a type of vitamin D, one required admission to the ICU, while 13 of 26 untreated people required admission to the ICU.

“Our pilot study demonstrated that administration of a high dose of calcifediol or 25-hydroxyvitamin D… significantly reduced the need for ICU treatment of patients requiring hospitalization due to proven COVID-19,” the study authors concluded.

Dr. Luigi Gennari, an associate professor in the department of medicine, surgery, and neurosciences at the University of Siena in Italy, recently presented data at a meeting of the American Society for Bone and Mineral Research showing a possible link between low vitamin D levels and risk of more serious COVID-19 infections.

The Italian researchers said that people who were admitted to the ICU at San Luca Hospital in Milan with severe COVID-19 symptoms had lower levels of 25-hydroxyvitamin D and higher levels of interleukin-6 (a protein produced by the body associated with inflammation) than those hospitalized with milder symptoms (non-ICU).

People who died from COVID-19 at the hospital also were more likely to have lower vitamin D levels than those who survived, the study found.

“Vitamin D plays a very important role in keeping us healthy and fighting illness in the least destructive way possible” by moderating the immune response without provoking an immune overreaction such as the “cytokine storm” often associated with severe COVID-19 illness, according to Dr, Manisha Singal, an internal medicine physician and the chief medical officer at Bridgepoint Hospital in Washington, D.C.

“It steers the immune system away from highly inflammatory pathways and toward a pathway that is more regulated,” Singal told Healthline.

Singal said that while it’s best to get vitamin D from natural sources, supplements also can be effective in boosting the immune system.

“You’re going to get enough vitamin D if you eat a relatively healthy meal and get some sunlight,” she said.

Singal also recommended getting vitamin D levels tested by a physician.

“In times like these it’s more important than ever to know what’s in our bodies,” she said. “Vitamin D can keep exposure to COVID-19 from becoming an infection that can cause you and other people harm.”