Higher levels of vitamin D than traditionally considered sufficient may help prevent COVID-19 infection – particularly in Black patients, shows a new single-center, retrospective study looking at the role of vitamin D in prevention of infection.
The study, published recently in JAMA Network Open, noted that expert opinion varies as to what “sufficient” levels of vitamin D are, some define this as 30 ng/mL, while others cite 40 ng/mL or greater.
In their discussion, the authors also noted that their results showed the “risk of positive COVID-19 test results decreased significantly with increased vitamin D level of 30 ng/mL or greater when measured as a continuous variable.”
“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, David Meltzer, MD, chief of hospital medicine at the University of Chicago, said in a press release from his institution.
“These findings suggest that randomized clinical trials to determine whether increasing vitamin D levels to greater than 30-40 ng/mL affect COVID-19 risk are warranted, especially in Black individuals,” he and his coauthors said.
Vitamin D at time of testing most strongly associated with COVID risk
An earlier study by the same researchers found that vitamin D deficiency (less than 20 ng/mL) may raise the risk of testing positive for COVID-19 in people from various ethnicities, as reported by this news organization.
Data for this latest study were drawn from electronic health records for 4,638 individuals at the University of Chicago Medicine and were used to examine whether the likelihood of a positive COVID-19 test was associated with a person’s most recent vitamin D level (within the previous year), and whether there was any effect of ethnicity on this outcome.
Mean age was 52.8 years, 69% were women, 49% were Black, 43% White, and 8% were another race/ethnicity. A total of 27% of the individuals were deficient in vitamin D (less than 20 ng/mL), 27% had insufficient levels (20-30 ng/mL), 22% had sufficient levels (30-40 ng/mL), and the remaining 24% had levels of 40 ng/mL or greater.
In total, 333 (7%) of people tested positive for COVID-19, including 102 (5%) Whites and 211 (9%) Blacks. And 36% of Black individuals who tested positive for COVID-19 were classified as vitamin D deficient, compared with 16% of Whites.
A positive test result for COVID-19 was not significantly associated with vitamin D levels in white individuals but was in Black individuals.
In Black people, compared with levels of at least 40 ng/mL, vitamin D levels of 30-40 ng/mL were associated with an incidence rate ratio of 2.64 for COVID-19 positivity (P = .01). For levels of 20-30 ng/mL, the IRR was 1.69 (P = 0.21); and for less than 20 ng/mL the IRR was 2.55 (P = .009).
The researchers also found that the risk of positive test results with lower vitamin D levels increased when those levels were lower just prior to the positive COVID-19 test, lending “support [to] the idea that vitamin D level at the time of testing is most strongly associated with COVID-19 risk,” they wrote.