May 18, 2020 — Could having a healthy blood level of vitamin D help you avoid the intensive care unit and death if you become infected with COVID-19?
Several groups of researchers from different countries have found that the sickest patients often have the lowest levels of vitamin D, and that countries with higher death rates had larger numbers of people with vitamin D deficiency than countries with lower death rates.
Experts say healthy blood levels of vitamin D may give people with COVID-19 a survival advantage by helping them avoid cytokine storm, when the immune system overreacts and attacks your body’s own cells and tissues.
The early research is not yet peer-reviewed, and other experts say scientific proof is lacking that vitamin D could prevent COVID-19 or make the infection milder.
Researchers are trying to figure that out — at least 8 studies are listed on clinicaltrials.gov to evaluate vitamin D’s role in preventing or easing COVID-19.
In the meantime, some people say there’s no harm in taking the vitamin as a precaution.
“I feel like if there is anything we can be doing at the moment to support our body, I am totally on board,” says Jackie Wilcox, 38, of Newburyport, MA, near Boston. Her family, including her husband and two children, are taking daily supplements.
How Did Researchers Start Looking at Vitamin D?
Vitamin D, produced when the sun hits your skin, has many other benefits, such as bone health. It’s also found in some foods and supplements.
Among recent studies finding a link between vitamin D levels and how severe COVID-19 is:
Researchers from the U.K. evaluated the average vitamin D levels and the number of COVID-19 cases, as well as the death rates, across 20 European countries. Countries with low average vitamin D blood levels in the population had higher numbers of COVID-19 cases and deaths, says study leader Petre Cristian Ilie, MD, PhD, research and innovation director at the Queen Elizabeth Hospital Foundation Trust in King’s Lynn, U.K.
At Northwestern University, researchers used modeling to estimate that 17% of those deficient in vitamin D would develop a severe COVID-19 infection, but only about 14% of those with healthy vitamin D levels. They estimated the association between vitamin D and severe COVID-19 based on a potential link between vitamin D deficiency and C-reactive proteins, or CRP, a surrogate marker for severe COVID-19
In a small study, Louisiana and Texas researchers evaluated 20 patients hospitalized with COVID-19, finding that 11 of the patients admitted to the ICU were vitamin D deficient, but only four of those not needing the ICU.
Indonesian researchers evaluated 780 documented cases of COVID-19 and found that most patients who died had vitamin D levels below normal.
Irish researchers analyzed European population studies and vitamin D levels, finding countries with high rates of vitamin D deficiency also had higher death rates from COVID-19. Those researchers asked the government to raise the vitamin D recommendations.
Pre-COVID-19 Research on Vitamin D’s Benefits
While the recent research on vitamin D and COVID-19 is just starting, other research has found that vitamin D supplements can help reduce the risk of respiratory infection. And researchers who looked back at the 1918-1919 influenza pandemic found that patients with healthy vitamin D blood levels were less likely to die.
The research linking vitamin D levels and COVID-19’s cytokine storm is also just starting, but not surprising, says Bart Roep, PhD, chair of the department of diabetes immunology at City of Hope, a cancer center in Duarte, CA. Vitamin D, he says, is ”the negotiator” because “it doesn’t suppress the immune system, it modulates it. Vitamin D makes the immune cells less inflammatory.”
While research finds that low vitamin D may affect how severe COVID-19 is, it’s not yet known if restoring vitamin D to normal levels would help as a treatment. Nor can anyone say for sure that having a healthy vitamin D level will help you avoid the virus.
A researcher from the University of Southeastern Philippines evaluated the vitamin D blood levels of 212 people diagnosed with COVID-19 and found the blood level of vitamin D was lowest in those in critical condition and highest in those with a milder infection. The conclusion of his paper, not peer-reviewed, is that supplements ”could possibly improve clinical outcomes of patients infected with COVID-19.”
The researchers also say that while there is ”overlap” between some groups at risk of being low in vitamin D and groups at high risk of getting COVID-19, including older adults, people of color, and those with chronic diseases, those associations are not proven.
Vitamin D also helps modulate cell growth and reduce inflammation. Some research suggests it could help prevent and treat diabetes, high blood pressure, and blood sugar problems, but the National Institutes of Health views that research as not clear-cut.
