Research to date is observational

There is preliminary, but growing, evidence that vitamin D may play a role in reducing the severity of Covid-19 infection and deaths, possibly by suppressing the risk for the runaway immune response known as cytokine storm.

Findings from an analysis published online early this week, ahead of peer review, suggested a possible link between vitamin D deficiency in elderly people and Covid-19 severity.

The researchers noted that high C-reactive protein (CRP) concentration has been identified as a possible indicator of cytokine storm and it is also associated with vitamin D deficiency.

They hypothesized that vitamin D supplementation may be protective against unregulated inflammation and cytokine storm in the setting of Covid-19, but this has not been shown in randomized, controlled trials.

Results from a retrospective cohort study of 780 cases of laboratory confirmed SARS-CoV-2 in Indonesia found a higher Covid-19 mortality rate in older males with below normal blood levels of vitamin D. The researchers concluded that vitamin D status was “strongly associated with Covid-19 mortality” after controlling for age, sex, and comorbidities.

And, widely reported observational research from Trinity College Dublin, published last week in the Irish Medical Journal, also linked vitamin D deficiency to greater Covid-19 severity.

The analysis, conducted by researchers from the Irish Longitudinal Study on Aging, examined vitamin D status and Covid-19 infection and mortality by country among older adults in Europe.

Counter-intuitively, the researchers found that older adults residing in lower latitude countries that received more sunlight, such as Spain and Italy, tended to have lower mean concentrations of 25-hydroxy vitamin D [25(OH)D] and higher rates of vitamin D deficiency. These are the European countries that have also been hardest hit by the novel coronavirus, with the highest infection and death rates.

Older people residing in northern latitude countries such as Norway, Finland, and Sweden tended to have higher mean 25(OH)D levels, as well as lower SARS-CoV-2 infection and death rates.

Researchers Rose Anne Kenny, MD, and colleagues wrote that observational research found “Covid-19 infection and death rates appear to be higher in ethnic minority populations with darker skin, which research has shown to be at much higher risk for vitamin D deficiency.”

“The circumstantial and experimental evidence suggests that vitamin D may have an important supportive role for the immune system, particularly in regulating cytokine response to pathogens,” Kenny and colleagues wrote, adding that “there is a strong plausible biological hypothesis and evolving epidemiological data supporting a role for vitamin D in Covid-19.”

They added that while randomized, controlled trials will be necessary to confirm this association, such trials are “impractical during lock-down.”

“Observational studies correlating vitamin D at time of hospital admission with subsequent outcome would be extremely valuable and should be urgently pursued,” they wrote. “In the meantime, we recommend that more publicity be given to current guidelines for vitamin D dietary intake and supplementation as denoted by public health agencies in the USA, UK and Europe.”

While agreeing that more rigorous studies examining whether vitamin D plays a role in Covid-19 severity are warranted, family medicine clinician Donald Ford, MD, of Cleveland Clinic, told BreakingMED that the evidence supporting the link remains weak.

Ford said he is especially concerned that the media reports touting vitamin D supplementation as a potential Covid-19 prophylactic or treatment will give people the idea that they are protected from the virus if they take vitamin D.

“We don’t know if taking vitamin D or any other supplement will have an impact on patients, so we should proceed cautiously and thoughtfully, and treat each patient on an individual basis,” Ford said.

He added that testing all patients for vitamin D deficiency remains problematic.

“There is no recommendation to screen everybody to determine their vitamin D level, and the reason for this is there is great uncertainty and disagreement about what a good vitamin D level is,” he said.

Ford said the significant variability in symptoms and the severity of those symptoms among patients infected with SARS-CoV-2 highlights how little is known about the illness.

“One of the things about this virus that is so perplexing is why it seems to have a completely different course in different people,” he said. “We don’t know why one person who gets it will have mild illness and another will end up in the ICU. All of these factors need to be studied.”

  1. There is preliminary, but growing, evidence that vitamin D may play a role in reducing the severity of Covid-19 infection and deaths, possibly by suppressing the risk for the runaway immune response known as cytokine storm.

  2. Be aware that these data are observational, and one expert suggests that screening everyone for vitamin D level is problematic as there is great uncertainty and disagreement about what a good vitamin D level is.

Salynn Boyles, Contributing Writer, BreakingMED™

The researchers declared no funding source nor relevant conflicts of interest related to this study.

Cat ID: 190

Topic ID: 79,190,190,926,927,94,151,928,925,934