There is a clear link between low vitamin D levels and an increased risk of being hospitalised by COVID-19
As the latest wave of COVID-19 shows no signs of abating, University of South Australia experts say it's not just booster shots that could offer protection - healthy levels of vitamin D may also play a role.
In new research conducted in partnership with the King's College London and Guy's and St Thomas' NHS Foundation, researchers found a clear link between low vitamin D levels and an increased risk of being hospitalised by the virus.
No association was found between low vitamin D and the risk of catching COVID-19.
The study assessed more than 150,000 participants in the UK Biobank, undertaking analyses to determine whether the risk of COVID-19 was higher among people with Vitamin D deficiency (<25nmol/L in their blood) and vitamin D insufficiency (25-49 nmol/L) compared with those who had normal levels of Vitamin D (50+ nmol/L). They also compared risk of being hospitalised due to COVID-19 across these three groups.
In Australia, nearly a quarter of adults - about four million people - are vitamin D deficient. Globally, about one billion people have vitamin D deficiency, with 50% of the population showing insufficient vitamin D levels.
Australian-based researcher and epidemiologist, UniSA's Dr Kerri Beckmann, says the findings could identify vulnerable people and guide future public health advice.
"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," Dr Beckmann says.
"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 explored associations between vitamin D and COVID-19 outcomes among cancer patients, as well as across different ethnic groups.
People of Asian or African/Afro-Caribbean heritage were found to have a slightly higher risk of infection if they had low vitamin D levels, though the association between low vitamin D and severe illness was only seen in people of Caucasian backgrounds.
No association was found between vitamin D and COVID-19 outcomes among people previously diagnosed with cancer, though researchers caution this may reflect the smaller sample size.
Dr Beckmann says that while risk from COVID-19 has lessened over time, the virus remains a public health concern.
"COVID-19 may not be the threat it once was, but it still affects peoples' well-being," Dr Beckmann 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."
