You may have heard about recent studies that have come to similar conclusions: vitamin D deficiency may be linked to more severe cases of COVID-19. Can a vitamin D supplement help protect you? Perhaps. But first, it’s important to understand what vitamin D deficiency means, how vitamin D works in your body, and how much you really need.

The Latest Studies
Data from 20+ countries showed a higher rate of severe COVID-19 cases and deaths in countries where people had lower levels of vitamin D than in countries where people had higher levels of the nutrient.

Up first, researchers at Northwestern University looked at data on the admission, recovery, and mortality rates for patients with COVID-19 in China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the UK, and the United States. They compared this with data on the levels of vitamin D in the population in those countries before the pandemic and found that vitamin D deficiency correlated with higher rates of complications and mortality due to COVID-19.

“Our analysis shows that it might be as high as cutting the mortality rate in half,” lead researcher Vadim Backman of Northwestern University said. “It will not prevent a patient from contracting the virus, but it may reduce complications and prevent death in those who are infected.”

Next came a study published in the journal Aging Clinical and Experimental Research, where researchers from the UK found that among 20 European countries, those with higher average levels of vitamin D had fewer coronavirus cases and lower mortality rates.

While these studies both show correlations between vitamin D levels and severity of COVID-19 in these populations, more research is needed to determine if this is why some people are more vulnerable to complications from the virus than others.

Vitamin D Deficiency
Vitamin D deficiency can occur for a number of reasons:

  • You don’t consume enough vitamin D in your diet. This can happen if you follow a strict vegan diet, as most of the natural sources are animal-based (fish, egg yolks, fortified milk, etc.).
  • Limited exposure to sunlight. Your body makes vitamin D when your skin is exposed to sunlight, so being homebound, living in northern latitudes, wearing long robes or head coverings for religious reasons, etc., can set you up for a deficiency in this nutrient.
  • You have dark skin. Melanin pigment reduces the skin’s ability to make vitamin D in response to sunlight exposure. Some studies show that older adults with darker skin are at high risk of low vitamin D levels.
  • Your kidneys cannot convert vitamin D. In aging people, the kidneys are less able to convert vitamin D to its active form, thus increasing their risk of vitamin D deficiency.
  • Medical conditions affecting the digestive tract may decrease your ability to adequately absorb vitamin D. I.e. Crohn’s disease, cystic fibrosis, and celiac disease can affect your intestine’s ability to absorb vitamin D from food.
  • Obesity. Vitamin D is extracted from the blood by fat cells, altering its release into the circulation. People with a body mass index of 30 or greater often have low blood levels of vitamin D.

What does this all mean? It turns out that researchers found a strong correlation between vitamin D deficiency and a complication known as a cytokine storm: when the immune system goes into overdrive.

“Cytokine storm can severely damage lungs and lead to acute respiratory distress syndrome and death in patients,” Ali Daneshkhah, a postdoctoral research associate at Northwestern and the lead author of the study, said in a press release. “This is what seems to kill a majority of COVID-19 patients, not the destruction of the lungs by the virus itself. It is the complications from the misdirected fire from the immune system.”

Do I need vitamin D?
Vitamin D prevents our immune systems from becoming dangerously overactive, and so healthy levels of vitamin D may protect against developing severe complications from COVID-19, including death. However, the researchers stress that this doesn’t mean that we should all start taking vitamin D supplements.

“While I think it is important for people to know that vitamin D deficiency might play a role in mortality, we don’t need to push vitamin D on everybody,” said Vadim Backman, a professor of biomedical engineering at Northwestern who led the research. “It will not prevent a patient from contracting the virus, but it may reduce complications and prevent death in those who are infected.”

If you have the risk factors for a vitamin D deficiency, it may be important to ensure you’re modifying your lifestyle to consume or create enough vitamin D in your body or begin taking a vitamin D supplement. You can also have a blood test to determine the levels of vitamin D in your body and then create a plan with your doctor or consult with a Local Health pharmacist.

Vitamin D supplements are available at Local Health pharmacies, as well as on our website at