Data published in PLoS ONE indicated that, compared to people with sufficient levels of vitamin D (blood level 25-hydroxyvitamin D of at least 30 ng/mL), people with a vitamin D deficiency (blood level 25-hydroxyvitamin D less than 20 ng/mL) have a 54% higher SARS-CoV-2 positivity rate.
The new study adds to the wave of scientific publications suggesting that vitamin D3 supplementation could be a potentially promising and safe approach to reduce risk of COVID-19 infections and deaths. Meta-analyses of randomized clinical trials (RCTs) have shown that vitamin D3 supplementation reduces the risk of acute respiratory tract infections.
“Our findings provide further rationale to explore the role of vitamin D supplementation in reducing the risk for SARS-CoV-2 infection and COVID-19 disease,” wrote the researchers, led by Harvey Kaufman, MD, from Quest Diagnostics and Michael Holick, PhD, MD, professor of Medicine, Physiology and Biophysics and Molecular Medicine at Boston University Medical Campus.
“If controlled trials find this relationship to be causative, the implications are vast and would present a cheap, readily-available method for helping prevent infection, especially for those with vitamin D deficiency. This could be of increased importance for the African American and Latinx community, who are disproportionately affected by both COVID-19 and vitamin D deficiency.
“In the interim, the authors recommend responsible vitamin D supplementation based on personal needs, risk factors, and advice from personal physicians in accordance with existing Endocrine Society Guidelines.”
The sunshine vitamin
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and the active form 1,25-dihydroxyvitamin D (1,25(OH)2D).
While our bodies do manufacture vitamin D on exposure to sunshine, the level of solar radiation in some northern countries is so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
To achieve a 25(OH)D blood levels of at least 30 ng/mL, the Endocrine Society Guidelines recommends infants, children and adults receive 400-1000 IUs, 600-1000 IUs and 1000-1500 IUs of vitamin D daily respectively. Requirements for obese adults are 2-3 times higher.
For the new study, the researchers analyzed data from 191,779 patients from all 50 states with SARS-CoV-2 results and matching 25(OH)D results from the preceding 12 months. The coronavirus tests were performed between mid-March and mid-June, 2020.
The overall SARS-CoV-2 positivity rate was 9.3%.
When the researchers separated the individual according to 25(OH)D levels they found that the SARS-CoV-2 positivity rate was higher for those with vitamin D deficiency, compared to those with adequate or higher vitamin D levels.
Moreover, geographical analysis indicated that people living in predominantly African-American and Hispanic zip codes were not only more likely to be vitamin D deficient but also to have a higher risk of infection.
Overall, the data indicated that for every ng/mL increased in 25(OH)D, the positivity risk for SARS-CoV-2 decreased by 1.6%.
“The risk of SARS-CoV-2 positivity continued to decline until the serum levels reached 55 ng/mL,” wrote the researchers. “This finding is not surprising, given the established inverse relationship between risk of respiratory viral pathogens, including influenza, and 25(OH)D levels.”
Also in the literature
Earlier this year, researchers from Trinity College in Dublin, Ireland suggested that vitamin D deficiency plays an important role in the severity of COVID-19 infections.
Writing in Alimentary Pharmacology and Therapeutics, the Trinity College scientists stated: “… the evidence supporting a protective effect of vitamin D against severe COVID‐19 disease is very suggestive, a substantial proportion of the population in the Northern Hemisphere will currently be vitamin D deficient, and supplements, for example, 1000 international units (25 micrograms) per day are very safe.
“It is time for governments to strengthen recommendations for vitamin D intake and supplementation, particularly when under lock‐down.”
In addition, just this month, a team of scientists from the University of Chicago reported results from a retrospective study of 489 UChicago Medicine patients whose vitamin D level was measured within a year before being tested for COVID-19.
The UChicago Medicine team found that patients who had vitamin D deficiency that was not treated were almost twice as likely to test positive for the COVID-19 coronavirus compared to patients who had sufficient levels of the vitamin.
Source: PLoS ONE
15(9): e0239252, doi: 10.1371/journal.pone.0239252
“SARS-CoV-2 positivity rates associated with circulating 25-hydroxyvitamin D levels”
Authors: H.W. Kaufman et al.