CHICAGO — New research is adding to the growing amount of evidence that vitamin D may help beat back the risk of contracting COVID-19. Researchers from the University of Chicago Medicine say this is especially true for African-Americans.
Their study shows, however, that the same drop in the risk of infection did not occur in whites taking vitamin D supplements. Previous studies have discovered that around 80 percent of COVID-19 patients have 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,” lead author Dr. David Meltzer says in a university release.
The study analyzed over 3,000 patients in Chicago, measuring their vitamin D levels within two weeks of a COVID-19 test. Scientists consider levels of at least 30 ng/ml (nanograms per milliliter) “sufficient.” However, Black participants with 30 to 40 ng/ml of vitamin D had more than two and half times greater risk of catching the virus than those with 40 ng/ml or more in their systems. Overall, they had a 7.2-percent chance of testing positive for COVID. That’s 2.64 times higher than the rest of the general population.
People can get vitamin D through their diet or supplements. The nutrient is also produced by the body in response to sunlight exposure. Most people, especially those with darker skin, tend to be deficient in vitamin D production. Roughly half of the world’s population has levels below 30 ng/ml.
“Lifeguards, surfers, those are the kinds of folks who tend to have more than sufficient vitamin D levels,” Dr. Meltzer says. “Most folks living in Chicago in the winter are going to have levels that are well below that.”
The findings, published in JAMA Open Network, build on an earlier trial suggesting less than 20 ng/ml of vitamin D raises the risk of COVID infection.
“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,” the Chief of Hospital Medicine at UChicago Medicine adds.
‘We don’t know why’ COVID-19 is connected to vitamin D levels
Meltzer says he was motivated to study this link after seeing an article more than a year ago reporting people taking vitamin D supplements had much lower rates of viral respiratory infections. He decided to examine data collected at University of Chicago Medicine on the coronavirus to determine the role the nutrient might be playing.
“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,” Dr. Meltzer explains. “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,” the lead author continues.
Vitamin D supplements are relatively safe to take. However, excessive consumption has a connection to hypercalcemia — a condition in which calcium builds up in the bloodstream. It can cause nausea, vomiting, weakness, and frequent urination. If left unchecked, it can lead to bone pain and kidney stones.
“Currently, the adult recommended dietary allowance for vitamin D is 600 to 800 international units (IUs) per day,” Dr. Meltzer advises. “The National Academy of Medicine has said that taking up to 4,000 IUs per day is safe for the vast majority of people, and risk of hypercalcemia increases at levels over 10,000 IUs per day.”
International health officials recommend taking 10 micrograms of vitamin D — the equivalent of one salmon fillet — a day to keep bones and muscles healthy in the winter. One of the challenges of the current study is it is difficult to determine exactly how vitamin D may be supporting immune function.
“This is an observational study,” Meltzer concludes. “We can see that there’s an association between vitamin D levels and likelihood of a COVID-19 diagnosis, but we don’t know exactly why that is, or whether these results are due to the vitamin D directly or other related biological factors.”
Prompted by the fresh evidence, the researchers are now conducting two studies to learn if taking a daily supplement can help prevent COVID-19 or decrease the severity of its symptoms.
SWNS writer Mark Waghorn contributed to this report.