Can Vitamin D Reduce Your Risk of Severe COVID-19 From Omicron?
There has been a lot of talk about the role of vitamin D in COVID-19, practically ever since the pandemic began. But a new study has found there may be a link between your vitamin D status and your risk of developing a severe case of the virus from Omicron.
The study, which was published in PLOS One, analyzed data from 1,176 patients admitted to a hospital in Israel with COVID-19 between April 2020 and February 2021. Of those, 253 had records of their vitamin D levels before they were infected.
The researchers found that people who had COVID-19 that was classified as “severe or critical” were more likely to have lower levels of vitamin D. In fact, people with vitamin D deficiency, which researchers defined as being less than 20 ng/mL, were 14 times more likely to have severe or critical disease than those who had higher vitamin D levels. They were also more likely to die of COVID-19: 25.6% of those who were deficient in vitamin D died of COVID-19 vs. the 2.3% of patients who were not deficient in the vitamin.
Based on those metrics, about half of the people in the study were vitamin D deficient. “Among hospitalized COVID-19 patients, pre-infection deficiency of vitamin D was associated with increased disease severity and mortality,” the researchers concluded.
There has been mixed data on the role of vitamin D and COVID-19, making it hard to know what to think. Here’s what experts have to say.
First, why is vitamin D such an important nutrient?
Vitamin D is a fat-soluble vitamin that’s produced in the body when ultraviolet rays from the sun strike the skin and trigger something called vitamin D synthesis, according to the National Institutes of Health (NIH).
“Many people don’t realize that vitamin D impacts many different tissues and organs in the body,” says Bruce Troen, M.D., a vitamin D researcher and professor of medicine at the University at Buffalo.
Vitamin D has several roles in your body. It promotes the absorption of calcium in the gut, supporting strong bones. It can also reduce inflammation in the body and help regulate cell growth, immune function, and the metabolism of blood sugar in your body, the NIH says.
Worth noting: Most people don’t get enough of it. In fact, research suggests that 40% of adults in the U.S. could be vitamin D deficient.
How much vitamin D do you need?
Like most vitamins and nutrients, there are different recommended intakes depending on your age, sex, and lifestyle factors, like whether you’re pregnant or breastfeeding.
However, the recommendations for adults between the ages of 18 and 70 are generally the same. The NIH suggests that people who fall into this range strive to get 15 micrograms or 600 IU of vitamin D a day.
But there is no universally accepted amount, and other organizations, like the International Osteoporosis Foundation, recommend going up to 1,000 IU or higher if you have obesity, have osteoporosis, limited sun exposure, or have malabsorption.
When vitamin D levels are measured via blood tests, the NIH says that a range of 12 to under 20 ng/mL is considered “inadequate” for bone and overall health in otherwise healthy people while 20 or above is “generally considered adequate” for bone and overall health. However, having blood levels of more than 50 ng/mL is linked to a potentially bad impact on your health and can cause symptoms like nausea, vomiting, muscle weakness, neuropsychiatric disturbances, pain, loss of appetite, dehydration, excessive thirst, and kidney stones.
It’s possible to get vitamin D from foods, although very few naturally contain the vitamin. According to the NIH, the flesh of fatty fish (like trout, salmon, tuna, and mackerel) and fish liver oils are the best sources. However, beef liver, mushrooms, cheese, and egg yolks have small amounts of the vitamin, too.
Can vitamin D help protect you from Omicron and severe COVID-19?
It’s important to point out that the latest study just found a link between severe COVID and low vitamin D levels—it didn’t prove that you’re going to have more severe COVID if you’re deficient in vitamin D and you happen to contract the virus and vice versa.
But not every study has had similar results. A Nutrition Journal study published in 2021 found no link between the severity that people experienced with COVID-19 and their vitamin D levels. Another pre-print study published in November 2020 also found that patients hospitalized with COVID-19 didn’t get a benefit from taking vitamin D supplements.
But a small study from Spain’s University of Grenada that analyzed 76 people with COVID-19 found a positive association between vitamin D and disease severity. Of the 50 who were treated with vitamin D, only one needed to be admitted to the ICU, compared to 13 of the 26 people who weren’t treated with the vitamin. The study concluded that vitamin D supplementation “significantly reduced the need for ICU treatment of patients requiring hospitalization due to proven COVID-19,” the researchers wrote.
A JAMA study also found that people who tested positive for COVID-19 were more likely to be deficient in vitamin D. The cohort study, which analyzed data from 489 people who had their vitamin D level measured the year before they were tested for COVID-19, found that the risk of testing positive for the virus was 1.77 times greater for people who were likely still deficient in vitamin D, compared with those who likely had enough vitamin D.
“These findings appear to support a role of vitamin D status in COVID-19 risk,” the study authors wrote, noting that more research is needed to determine whether certain people with vitamin D deficiency should consider supplementation.
“There is lots of physiological and biological evidence that suggestions vitamin D can make a difference,” says David Meltzer, Ph.D., M.D., a professor of medicine at the University of Chicago and lead author of the JAMA study. “But do we know for sure? No.”
Dr. Meltzer, who says he takes a vitamin D supplement, notes that “at a bare minimum, people should not be deficient in vitamin D.”
“Vitamin D deficiency, whatever its cause, has an established risk factor for respiratory infections for some time and there has been data from the early days of the pandemic that it applies to SARS-CoV2 as well,” says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. He points out that the British government even mailed vitamin D supplements to residents at the height of the pandemic. “Vitamin D plays an important role in immune system function,” he adds.
But vitamin D can be a tricky nutrient to draw conclusions about, says Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. “Vitamin D is the great tease in medicine,” he says. “There are endless trials have looked at associations of vitamin D levels and various outcomes including cancer, cardiovascular health and, most recently, COVID. While some of these trials show you have more bad outcomes when people have lower levels, when randomized controlled trials have been done, vitamin D has never panned out to beneficial.”
Dr. Russo says it’s unclear why there seems to be a link between severe COVID and low vitamin D levels. “We could speculate that perhaps people with lower vitamin D levels may be couch potatoes who don’t get outside enough, don’t get enough exercise, and have poor nutritional habits,” he says. Those could raise a person’s risk of having obesity, type 2 diabetes, or other factors that can increase their risk of severe COVID, he says. But, Dr. Russo adds, “it’s speculation at this point.”
Still, he says, “people that have abnormally low vitamin D levels should get on a supplement.”
Should you take vitamin D to lower your risk of severe COVID?
Experts do not know at this point how much a vitamin D supplement will help a person who isn’t deficient. “Someone who has sufficient levels of vitamin D in their body will probably not benefit,” Dr. Adalja says. “But if you have inadequate levels, you may be more likely to be infected.”
There are still a lot of questions around how vitamin D can impact a person’s risk of contracting COVID-19, plus how much someone should even take. “We all need to be aware that our knowledge of what the right levels of vitamin D are with respect to infection, including COVID-19, are quite limited,” Dr. Meltzer says.
If you want to take a vitamin D supplement, it likely won’t hurt, Dr. Troen says, noting that he does. “We have tantalizing information that suggests there is a link between vitamin D status and COVID,” he says. “There’s little harm and potential benefit in taking vitamin D.”
It’s also unlikely that you’ll have symptoms if you’re deficient in vitamin D, says Sylvia Christakos, Ph.D., a professor in the Department of Biochemistry & Molecular Biology at Rutgers University. “You just have to get your vitamin D levels checked,” she says.
For what it’s worth, Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, also said during an Instagram Live interview with Jennifer Garner that he takes vitamin D supplements.
“If you’re deficient in vitamin D, that does have an impact on your susceptibility to infection,” Dr. Fauci said. “I would not mind recommending, and I do it myself, taking vitamin D supplements.”
Okay, what about other infections, like a cold or the flu?
The research there is a little more clear. One analysis of data from 11,321 people published in the BMJ found that those who took vitamin D supplements on a daily or weekly basis were less likely to develop respiratory tract infections than those who didn’t take the supplement. The researchers also discovered that people who had the highest vitamin D deficiencies saw the most benefit.
Another systematic review and meta-analysis of 5,660 people published in PLOS One found that vitamin D supplementation had a “protective effect” against respiratory tract infections, with a daily dose being the most effective.
“It’s generally accepted that having a normal level of vitamin D is important for proper immune system function, and that’s true with respiratory viruses,” Dr. Adalja says.
How to get enough vitamin D
Talk to your doctor. They can give you a blood test that will determine if you are low in vitamin D and by how much, Dr. Adalja says. That can help determine how much you should take as a supplement, if you even need to take a supplement.
But remember: Taking a vitamin D supplement alone won’t prevent COVID-19 or automatically cause you to have a more mild case of Omicron.
“People should not get distracted by vitamin D and assume that, if they take it, they don’t need to wear a mask and get vaccinated,” Dr. Russo says.
Dr. Meltzer agrees. “If you believe that taking vitamin D is a good thing to do, and that it may decrease your risk of contracting COVID-19 and improve your outcomes if you get it, you should also be doing other things to avoid getting COVID-19, like wearing a mask, practicing social distancing, and washing your hands regularly,” Dr. Meltzer says. “Vitamin D is not a substitute for those things. It’s an accompaniment.”
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