Getting enough vitamin D may protect you against the flu, a study has suggested.

Vitamin D, often called the “sunshine vitamin” because it is made by the body using sunlight, is found in food such as oily fish, red meat, and egg yolks.

However, due to a lack of daylight hours in UK winters around one in six people in theUK have vitamin D levels below government recommendations.

It’s long been known to be vital for bone and muscle health, but a new study led by the University of Surrey has found a correlation between vitamin D deficiency and the risk of hospital admissions for respiratory infection.

In the study, published in the American Journal of Clinical Nutrition, researchers suggested that people with a severe Vitamin D deficiency were more likely to be admitted to hospital with respiratory conditions such as bronchitis and pneumonia.

Vitamin D is made by the body using sunlight and is found in food such as oily fish, red meat, and egg yolks (Getty Images/iStockphoto)

Vitamin D is thought to have “antibacterial and antiviral properties” which help to reduce the risk of respiratory tract infections, according to Abi Bournot, lead author from the University of Surrey.

“This research attaches hard data to support the theory. Despite its importance to our overall health, many people are deficient and do not meet the government’s recommended intake of 10 micrograms of vitamin D per day,” she added.

For the study, researchers from Universities of Surrey, Oxford and Reading analysed data on 36,000 adults in the UK to find out how vitamin D levels affected the rate of hospital admissions with respiratory infections.

Previous studies have linked a lack of vitamin D to an increased risk of Covid, but here researchers looked at both bacterial and viral illnesses such as flu, pneumonia and bronchitis.

Results revealed those with a severe vitamin D deficiency, classed as having a concentration below 15nmol/L in the blood were 33 per cent more likely to be admitted to hospital with a respiratory infection. That’s in comparison to people who had optimal levels of more than 75nmol/L.

For every 10nmol/L increase in vitamin D in the blood, the number of people admitted to hospital for respiratory illnesses reduced by 4 per cent.

Study author Dr Andrea Darling, at the University of Surrey, said that respiratory infections are a “major threat to public health” which can lead to hospitalisation and put a strain on health services. But explained eating vitamin D fortified foods could reduce this risk and reduce pressure on the NHS.