VITAMIN D DEFICIENCY LINKED TO HIGHER COVID-19 HOSPITALISATION RISK

Low levels of vitamin D may increase the risk of being hospitalised with COVID-19, according to new research involving more than 150,000 people.

As Australia weathers another wave of COVID-19, new research suggests that maintaining healthy levels of vitamin D could offer added protection – not from catching the virus, but from being seriously affected by it.

A joint study led by the University of South Australia (UniSA), in collaboration with King’s College London and Guy’s and St Thomas’ NHS Foundation, has found a clear link between vitamin D deficiency and an increased risk of hospitalisation due to COVID-19.

Drawing on data from over 150,000 UK Biobank participants, researchers compared individuals with normal vitamin D levels (50+ nmol/L) to those with deficiency (<25 nmol/L) or insufficiency (25–49 nmol/L). While low vitamin D did not increase the risk of contracting COVID-19, it did significantly increase the chance of hospitalisation.

In Australia, nearly one in four adults – around four million people – are vitamin D deficient. Globally, that number swells to an estimated one billion.

“Vitamin D plays a key role in regulating the immune system, so it’s plausible that low levels may influence how the body responds to infections like COVID-19,” says UniSA’s Dr Kerri Beckmann, an epidemiologist and co-author of the study.

“Our study found that people with a vitamin D deficiency or insufficiency were more likely to be hospitalised with COVID-19 than those with healthy levels of Vitamin D – but they weren’t more likely to catch the virus in the first place.”

The study also investigated outcomes among cancer patients and across different ethnic groups. While no link between vitamin D and COVID-19 outcomes was found in cancer patients (likely due to small sample size), some differences emerged between ethnicities.

People of Asian or African/Afro-Caribbean backgrounds were found to have a slightly higher infection risk if they had low vitamin D levels. Still, the link between deficiency and severe illness was observed only in Caucasian individuals.

Dr Beckmann emphasised that even with widespread vaccination, COVID-19 remains a health issue – particularly for those with underlying vulnerabilities.

“COVID-19 may not be the threat it once was, but it still affects people’s well-being,” she says.

“Understanding who is most at risk helps those individuals take extra precautions, including monitoring their vitamin D levels.

“It could be that people who are in poor health to start with may also have low vitamin D levels. So, at this stage, we don’t know whether vitamin D supplements in themselves could reduce the severity of COVID-19.

“It’s certainly an area worth exploring – especially as we continue to live with the virus.”

The study was a collaboration between UniSA, King’s College London, and Guy’s and St Thomas’ NHS Foundation, and adds to a growing body of evidence on the role of vitamin D in immune response.