While we’ve stayed physically distanced and isolated throughout the pandemic, there’s been a lot of hubbub about vitamin D and the new coronavirus. But is this relationship merely a coincidence, or should you be adding vitamin D to your COVID-19 tool kit?

We’ve done the vitamin D and coronavirus research for you to see just how vitamin D affects COVID-19.

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Marc Tran/Stocksy United

While we’re learning more about the new coronavirus every day, we do know that the new coronavirus attacks the respiratory system. And lo and behold, vitamin D supports the immune system and respiratory health. Here’s what some studies have found.

Immune system health

Vitamin D is super important to keep your immune system in tip-top shape.

Basically, according to research, vitamin D helps deploy an immune response when a potential infection attacks your body. It also helps gear up immune cells like T cells and macrophages to protect your body from invaders.

So if you have a weaker immune system, you’re naturally more prone to illnesses, which could include COVID-19.

Vitamin D deficiency

According to a 2020 article, vitamin D deficiency is often seen in people who have severe COVID-19 complications like:

  • pneumonia
  • severe acute respiratory distress syndrome
  • myocarditis (inflammation of the heart muscle)
  • cytokine storms (severe immune reactions causing inflammation)

All these conditions create underlying inflammation, which can be controlled by T regulatory lymphocytes (aka Tregs). Basically, these cells can regulate or suppress other immune system cells and control the immune response to fight an invading disease.

The same article noted that low levels of Treg cells are reported in people who have COVID-19, and vitamin D supplementation can increase Treg levels. So, the researchers suggest, if vitamin D can increase Treg levels, it might also be able to help reduce the severity of COVID-19. But right now this is just a theory.

Respiratory health

Back before the new coronavirus was around, a 2017 research review found that participants who took daily or weekly vitamin D supplements were more protected against acute respiratory tract infections. This was especially true for people who had a vitamin D deficiency.

With that in mind, it’s no wonder researchers wanted to see if vitamin D could help prevent COVID-19.

The short answer: We don’t know. Vitamin D is definitely not a substitute for masks and physical distancing for virus prevention. But research does suggest a few relationships between vitamin D levels and the new coronavirus that might make it a helpful coronavirus vitamin.

Recent research suggests a link between sun exposure and COVID-19 mortality. Countries located farther from the equator (and thus with less sun) had higher numbers of COVID-19 deaths, possibly because of the prevalence of vitamin D deficiency.

This evidence is circumstantial, which means that although fingers are being pointed at vitamin D deficiency, the connection to COVID-19 has not been proven.

Another 2020 study looked for an association between low vitamin D levels and COVID-19. Of the 7,807 people in the study, only about 10 percent tested positive for COVID-19, and almost 90 percent tested negative.

The people who tested positive had lower mean plasma vitamin D levels than those who tested negative, but the difference wasn’t significant. Positive levels averaged 19.00 ng/mL, and negative levels averaged 20.55 ng/mL. This minor difference doesn’t show much correlation between vitamin D levels and COVID-19.

Plus, low vitamin D level was dubbed an “independent risk factor,” which means it’s associated with the study outcome but there were other factors in play. These included being over 50 years old, being male, and being of low-medium socioeconomic status.

It’s possible that other correlations between vitamin D and the new coronavirus might make all these studies look like BS. But it’s a bit more complicated than that.

A lot of studies and reviews are showing a beneficial outcome, but nothing is set in stone because there are too many variables to consider.

One 2020 review shared other evidence factors that link vitamin D levels with the new coronavirus:

  • The outbreak happened in winter, when vitamin D levels are at their lowest.
  • The number of COVID-19 cases in the Southern Hemisphere near the end of summer was low (because the Southern Hemisphere has sunshine).
  • Vitamin D deficiency contributes to acute respiratory distress syndrome.
  • Fatality rates increase with age and chronic disease — both factors that are associated with low vitamin D levels.

The review ends by stating that randomized controlled trials and large population studies need to be done to evaluate these recommendations.

The Centers for Disease Control and Prevention (CDC) also states that people with certain medical conditions are at an increased risk of severe illness (hospitalization, intubation, or even death) from COVID-19.

Some of these conditions are:

  • cancer
  • chronic kidney disease
  • chronic obstructive pulmonary disease (COPD)
  • obesity or severe obesity
  • type 2 diabetes
  • pregnancy

Many of these conditions are also associated with a risk of vitamin D deficiency.

Research related to the new coronavirus is ongoing and constantly changing, but right now there isn’t much promising information to suggest that vitamin D can help treat COVID-19.

Researchers in a 2020 study said they had found reason to believe vitamin D might help treat COVID-19, but their data was flawed. The editors of the peer-reviewed journal published an “expression of concern” about the study’s questionable sample size and noted that only about 31 percent of the participants actually had tests confirming a COVID-19 diagnosis.

Taking a vitamin D supplement may not be the COVID-19 cure you were hoping for, but it still comes with a lot of benefits. Plus, about 50 percent of the world’s population doesn’t get enough vitamin D (meaning we need it, COVID or not).

Obviously, your immune system is crucial to fight infection, and vitamin D is necessary to keep that system strong. But vitamin D can also help keep your bones strong (potentially reducing fractures) and benefit your mental health.

If you’ve heard it once, you’ve heard it a thousand times: Some of the standard preventive measures for COVID-19 are physical distancing (at least 6 feet) and wearing a mask in public.

Other recommendations from the CDC:

  • Wash up. Wash your hands with soap and water, scrubbing for at least 20 seconds, especially after you sneeze, cough, or blow your nose. In a pinch, you can also use hand sanitizer that’s at least 60 percent alcohol.
  • Clean. Disinfect those frequently touched surfaces on the reg. This includes desks, phones, keyboards, countertops, doorknobs… the list could go on.
  • Monitor your health. Be aware of how you’re feeling and watch for symptoms such as fever, cough, or shortness of breath.

Although current research suggests a relationship between low levels of vitamin D and COVID-19, more research is needed.

Right now we can’t conclude that taking vitamin D can help prevent you from contracting the new coronavirus. Wearing a mask, physical distancing, and washing your hands are still your top options.

In the meantime, taking a vitamin D supplement probably won’t hurt, and it can help bolster your immune system, which might increase your chances of avoiding COVID-19. Most of us don’t get enough vitamin D anyway and could use a boost.

It’s a good idea to check with your healthcare provider before taking any new supplement, especially if you have any preexisting medical conditions or take any medications that could interact with the vitamin.