High Vitamin D Levels May Protect Against COVID-19

A report from the National Urban League suggests that Black Americans are infected with COVID-19 at nearly three times the rate as White Americans, and they are also twice as likely to lose their battle with the virus and die. 

“I believe that many factors contribute to this, including socioeconomic factors such as whether one has a job that allows one to work from home or enough economic resources to protect oneself, and access to healthcare. I think vitamin D may also contribute to differences in COVID-19 risk and outcomes by race and deserves serious attention as a contributor. We need to work on all these fronts,” says David Meltzer, MD, Ph.D., who is the lead author of the study and chief of hospital medicine at UChicago Medicine. 

Previous reports have revealed that those with vitamin D deficiency who were randomly assigned to receive supplementation experienced much lower rates of viral respiratory infections compared to those not receiving supplementation. These studies inspired this current investigation into the effects on COVID-19. 

“There’s a lot of literature on vitamin D. Most of it has been focused on bone health, which is where the current standards for sufficient vitamin D levels come from. But there’s also some evidence that vitamin D might improve immune function and decrease inflammation. So far, the data has been relatively inconclusive. Based on these results, we think that earlier studies may have given doses that were too low to have much of an effect on the immune system, even if they were sufficient for bone health, It may be that different levels of vitamin D are adequate for different functions,” explains Meltzer. 

According to Meltzer, the current dietary allowance for vitamin D is 600-800 IUs per day, but the National Academy of Medicine has said that taking this up to 4,000 IUs per day is typically safe for the majority of people, and the risk of hypercalcemia increases at levels exceeding 10,000 IUs per day. 

This study analyzed data from over 3,000 UChicago Medicine patients who had their vitamin D levels tested within 14 days before having a COVID-19 test. Levels of 30 ng/ml or more are generally considered to be sufficient, however, Black Americans with levels of 30-40 ng/ml were revealed to have a 2.64 times higher risk of testing positive than those with levels greater than 40 ng/ml, and these statistically significant associations of vitamin D levels with COVID-19 risk were not found among White Americans. 

“We do not know why these differences exist but several reasons come to mind. One is that White people in our sample may have been less likely to be in jobs or living situation that exposed them to the virus, so their risk is lower overall, and that would make it harder to see significant associations between vitamin D levels and the risk of COVID-19 even if the underlying biology was the same. Another is that White people tend to have higher vitamin D levels, so there are fewer White people with the lower vitamin D levels where vitamin D may make a difference in the risk of developing COVID-19. A third is that White people are more likely to have vitamin D binding proteins that allow vitamin D to be used by the immune system even when vitamin D levels are low. A fourth is that White people may less rapidly break down vitamin D than Black people so lower levels in the blood are more effective in White people than they would be in Black people,” explains Meltzer. 

Findings from this study expand on earlier studies showing that vitamin D deficiency may increase the risk of testing positive for COVID-19. Previous results were further supported by this study finding that those with a vitamin D deficiency had a 7.2% chance of testing positive for the virus. Additionally, another recent study found that over 80% of those diagnosed with COVID-19 had a vitamin D deficiency. 

“These new results tell us that having vitamin D levels above those normally considered sufficient is associated with decreased risk of testing positive for COVID-19, at least in Black individuals. This supports arguments for designing clinical trials that can test whether or not vitamin D may be a viable intervention to lower the risk of the disease, especially in persons of color,” said Meltzer. 

According to an interview with Meltzer and Nutraingredients, vitamin D helps to improve several aspects of the immune system that are important to fight against infection. “First, it improves innate immunity, the ability to fight off an infection one has never been exposed to before. Second, vitamin D helps adaptive immunity, the ability to fight off an infection one has been exposed to before, which may be beneficial in the later stages of even a first COVID-19 infection. Finally, vitamin D is an immunomodulator, which helps prevent the body from having too strong an inflammatory reaction to a COVID-19 infection that may result in symptoms such as shortness of breath.”

Most individuals, especially those with darker skin have lower levels of vitamin D, with roughly half of the world’s population having levels below 30 ng/ml, notes Meltzer, and there are several studies now suggesting that the risk/severity of COVID-19 may be related to the latitude one lives in, with those living in the Northern areas generally being at higher risk of developing COVID-19 or having a more severe outcome. 

“Lifeguards, surfers, those are the kinds of folks who tend to have more than sufficient vitamin D levels. Most folks living in Chicago in the winter are going to have levels that are well below that,” says Meltzer. 

The University of Chicago and Rush University are conducting 2 studies to investigate whether taking vitamin D supplements daily can help to prevent COVID-19 or decrease the severity of symptoms. To find out more visit: https://chess.uchicago.edu/vitamind/