Long COVID risk increases with low levels of vitamin D, according to study

15 May 2023 --- Researchers from the Vita-Salute San Raffaele University and IRCCS San Raffaele Hospital in Milan, Italy, have found that Long COVID risk increases when vitamin D levels are low. The research was presented at the 25th European Congress of Endocrinology in Istanbul, Türkiye (May 13-16). 

Including 100 hospitalized patients, 50 with and 50 without Long COVID, aged between 51 to 70 years old, the researchers measured vitamin D levels when admitted and six months after discharge. They found lower levels among those suffering from Long COVID than those who did not.

The results, published in the Journal of Clinical Endocrinology & Metabolism, were also more evident among those suffering brain fog symptoms – confusion, forgetfulness and concentration.

NutritionInsight speaks with Andrea Giustina, the study’s lead investigator and director of endocrinology and metabolism sciences at the University Vita-Salute San Raffaele, Milano, Italy, about the study findings.

“The strength of our study was its highly controlled environment with subjects who developed Long COVID and who did not match well for several clinical variables. As a result, the lower vitamin D levels in Long COVID are likely to represent a unique feature of Long COVID.”  

“I was relatively surprised by the statistically significant difference observed for vitamin D levels in a relatively small although highly controlled population. This may mean that what we described is likely a quite relevant finding,” he adds.

The researchers argue that Long COVID affects 50-70% of people hospitalized for COVID-19.Long COVID
Previous studies on the role of vitamin D in Long COVID were not conclusive mainly due to many confounding factors, argues Giustina. 

“The highly-controlled nature of our study helps us better understand the role of vitamin D deficiency in Long COVID and establish that there is likely a link between vitamin D deficiency and Long COVID.”

Lasting over 12 weeks post-infection, the researchers argue that Long COVID affects 50-70% of people hospitalized for COVID-19. Still, little is known about it. The study found vitamin D levels as an independent risk factor for Long COVID. 

“Our study shows that COVID-19 patients with low vitamin D levels are more likely to develop Long COVID, but it is not yet known whether vitamin D supplements could improve the symptoms or reduce this risk altogether,” adds Giustina. 

Scientists say that more extensive studies are needed to confirm the link. In the future, the team strives to determine if vitamin D dietary supplements can reduce long covid risk. 

Controversy on vitamin D
Recent neuroimaging studies found increased pulmonary and neurological inflammation in people who reported feeling Long COVID symptoms. Additionally, a neuroimaging analysis found reductions in the brain’s gray matter for many months following infection.

“Our data, if confirmed in large, interventional and randomized controlled trials, suggests that vitamin D supplementation could represent a possible preventive strategy in reducing the burden of COVID-19 sequelae [Long COVID],” reads the new study.

In September last year, two studies published in the British Medical Journal showed no association between a lowered risk of COVID-19 or respiratory tract infections for adults taking vitamin D supplements. However, there were limitations for both trials as vaccine implementation occurred during the same period.

The Council for Responsible Nutrition (CRN) responded to the two studies urging the public to be cautious toward the information.

“Reporting on this research that suggests vitamin D levels are not relevant to COVID-19 outcomes ignores the large body of research on this connection and downplays critical limitations of these studies,” Luke Huber, VP of scientific and regulatory affairs at CRN, said previously.

By Beatrice Wihlander

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