Taking vitamin D supplements throughout the winter really can help protect you against the flu, promising new research has found.
UK scientists found that people with a severe vitamin D deficiency were 33 per cent more likely to be hospitalised with a respiratory infection than those with adequate levels.
Publishing their findings in the American Journal of Clinical Nutrition, they advised: ‘Ensuring adequate intakes of vitamin D could have significant population-level influences on respiratory tract infection hospitalisation.’
They added: ‘Any ethnic population with a high prevalence of vitamin D deficiency should be targeted to disseminate information about prevention.’
The so-called sunshine vitamin is the only supplement recommended by the NHS for everyone to take daily during the autumn and winter.
And those who are at high risk of deficiency, including young children aged 1 to 4-years-old, and people with dark skin should take a daily supplement throughout the year.
Vitamin D helps to regulate the amount of calcium and phosphate in the body, helping to keep bones, teeth and muscles healthy.
And without sufficient levels, people are at risk of not only developing bone pain – known as osteomalacia – but severe infections like the flu.
Consuming 10 micrograms of vitamin D a day, in line with government guidelines, could protect you from flu experts say
In the largest study of its kind, researchers spearheaded by the University of Surrey, analysed UK Biobank data from 36,000 adults to uncover the link between levels of vitamin D and hospital admissions with respiratory infections.
These included a range of common viral and bacterial illnesses such as flu, pneumonia and bronchitis – which affect the airways and the lungs.
There have previously been reports about vitamin D reducing the risk of contracting Covid, but the health service warns there isn’t currently enough evidence to support this theory.
The researchers found that people with a severe vitamin D deficiency – classed as a blood concentration below 15nmol/L – were a third more likely to be admitted to hospital with these illnesses than those with optimal levels of 75nmol/L or more.
For each 10nmol/L increase in circulating vitamin D, the hospital admission rate for respiratory tract infections fell by an impressive 4 per cent.
Out of the 27,872 participants included in the final analysis, 2,255 patients were admitted to hospital with a respiratory infection.
Older adults are at a higher risk of developing these types of infection, with pneumonia and bronchitis ranking among the top 20 leading causes of death worldwide for individuals aged 50-74-years old.
This jumps to the top 10 for those over 75.
The NHS recommends that people with dark skin – for example from African, African-Caribbean or south Asian backgrounds – should consider taking a daily supplement containing 10 micrograms of vitamin D throughout the year
Abi Bournout, an expert in nutritional immunology, and lead author from the University of Surrey, said: ‘Vitamin D is vital to our physical wellbeing. Not only does it keep our bones and muscles healthy, its antibacterial and antiviral properties are also thought to help reduce the risk of respiratory tract infection that can lead to hospitalisation.
‘This research attaches hard data to support the theory,’ she added.
Despite this, over a billion people worldwide are deficient in vitamin D to some level, with almost a fifth of the UK population estimated to be lacking.
The main, natural sources of vitamin D are exposure to sunlight, and from foods like oily fish, red meat and egg yolks.
Ms Bournout continued: ‘Supplementation of the vitamin, especially in the winter months when exposure to sunlight is limited, is an effective way of increasing vitamin D and reducing the risk of serious respiratory tract infections.
‘This is particularly important for older people who are at higher risk of death from such infections, and ethnic minority communities in the UK, who are at higher risk of vitamin D deficiency.’
While supplements can help to boost vitamin D levels, experts say adequate sunlight exposure and a healthy diet that includes things like oily fish, red meat and fortified foods, are the best sources.
It comes following a slight increase in flu cases after two weeks of falling numbers, with more than 2,940 beds taken up by flu patients alone in the first week of the year.
Whilst flu cases have started to fall again, total bed occupancy is still worryingly high, officials say – with the cold weather and more injuries from slips and falls pushing some trusts to capacity.
