COVID-19: High vitamin D levels may protect Black people
Written by James Kingsland on April 1, 2021 — Fact checked by Catherine Carver, MPH
Share on PinterestResearchers reexamine the role of vitamin D in COVID-19. Igor Alecsander/Getty Images
- Previous research has linked vitamin D deficiency to a higher risk of getting COVID-19 and experiencing more severe disease, especially among Black and Hispanic individuals.
- A new observational study suggests that even “sufficient” vitamin D levels, as guidelines currently define them, are associated with a higher risk of COVID-19 for Black people.
- Current guidelines for assessing vitamin D status are based on maintaining bone health rather than immune function.
Vitamin D plays a wide range of roles in the body, including regulating calcium levels, maintaining healthy bones and teeth, and supporting the immune system.
In addition to getting vitamin D from dietary sources, the body can make its own in the skin through exposure to sunlight.
However, it can be difficult for people with dark skin and those with low exposure to sunlight to maintain sufficiently high levels of the vitamin, especially during the winter months.
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One study found that, overall, about 42% of people in the United States were deficient in vitamin D. The figure rose to 82% among Black people and 70% among Hispanic people.
Accumulating evidence has shown that people with deficient vitamin D levels are more likely to test positive for SARS-CoV-2, which is the virus that causes COVID-19. They may also be more likely to develop severe disease.
This association may partly explain why the pandemic has disproportionately affected Black, Hispanic, and other non-white populations.
Clinical trials have found that vitamin D supplements can help protect people against other respiratory infections resulting from viruses.
The research suggests that taking a vitamin D supplement can even reduce viral infections among people who are not deficient in the vitamin, based on the recommended intake in the current guidelines. These recommendations are based on the levels necessary to maintain healthy bones.
Dr. David Meltzer, Ph.D., and his colleagues at the University of Chicago, IL, wondered whether the same could be true of vitamin D and COVID-19.
Vitamin D blood tests
The researchers analyzed the medical records of 4,638 individuals who had a vitamin D blood test in the 12 months before having a PCR test for SARS-CoV-2 at the University of Chicago Medical Center (UChicago Medicine).
The researchers used the length of time since the vitamin D test and subsequent treatments to estimate the participants’ vitamin D levels 14 days before the PCR test.
In addition, they accounted for factors that are known to increase a person’s risk of COVID-19, such as age, sex, race, and medical conditions.
In total, 211 Black participants and 102 white participants tested positive for SARS-CoV-2.
The researchers discovered that among Black participants, the risk of testing positive was 2.64 times as high for those with a serum vitamin D level of 30–39.9 nanograms per milliliter (ng/ml) — a “sufficient” level — as it was for those with a level of at least 40 ng/ml.
In other words, there appeared to be a significant protective effect from having levels above the range that experts consider to be sufficient.
Among Black participants with a vitamin D level of at least 30 ng/ml, every incremental 1 ng/ml increase in the level of the vitamin led to a 5% decrease in the risk of testing positive for SARS-CoV-2.
“These new results tell us that having vitamin D levels above those normally considered sufficient is associated with decreased risk of testing positive for [SARS-CoV-2], at least in Black individuals,” says Dr. Meltzer, who is chief of hospital medicine at UChicago Medicine and lead author of the study.
“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,” he adds.
There were no statistically significant associations between vitamin D levels and the risk of testing positive for SARS-CoV-2 among white individuals.
The researchers attribute this to the relatively low number of positive SARS-CoV-2 tests among white people in their sample.
Similarly, the numbers of participants from other racial groups, including Hispanic people, were too small to yield statistically significant results.
The study appears in the journal JAMA Network Open.