High intakes of vitamins A, E, and D are linked to fewer respiratory illnesses, experts have suggested, as they called for further research into their effect on coronavirus.
A new long-term study involving 6,115 adults starting in 2008 suggests that taking the vitamins either through food or as a supplement may reduce the number of respiratory complaints.
It comes after Health Secretary Matt Hancock ordered a review into the use of vitamin D for preventing coronavirus after previously saying it did not appear to have any effect.
Those taking part in the latest study self-reported their vitamin intake and any respiratory issues, rather than them being diagnosed by a doctor.
Overall, there were 33 cases of respiratory complaints and researchers found that vitamin A and E intake from both diet and supplements was associated with a lower likelihood of them being reported.
Vitamin D intake from supplements, but not from diet, was also associated with fewer respiratory complaints.
Vitamin D is often referred to as the sunshine vitamin because, from about late March to the end of September, most people should be able to get all the vitamin D they need from sunlight.
But between October and early March people do not get enough and the NHS says adults and children aged four and over should take a daily supplement containing 10 micrograms of vitamin D during this time.
Meanwhile, children aged one to three should receive vitamin D supplements all year round.
The researchers for the latest study, including from Imperial College London, the London School of Hygiene and Tropical Medicine, said: “It is estimated that around a fifth of the general population in the UK have low vitamin D, and over 30% of older adults aged 65 years and above do not achieve the recommended nutrient intake.
“Our findings are consistent with the hypothesis that supplementation is critical to ensuring adequate vitamin D status is maintained and potentially indicate that intake of vitamin D from diet alone cannot help maintain adequate vitamin D status.”
The team said further research is needed “to assess the implications of the current study in the context of the current coronavirus disease” pandemic.
Shane McAuliffe, science communications lead for the NNEdPro Nutrition and Covid-19 Taskforce, which includes experts from the University of Cambridge, said: “While acknowledging the limitations of this data, it does add further to a growing body of interest and evidence for the role of vitamin D in respiratory health.
“Given our knowledge of the extent of vitamin D deficiency in the population, balanced with the low cost and low risk of adverse events, it seems sensible to provide supplementation of this key vitamin, particularly to those most likely to be deficient.”
The study was published in the journal BMJ Nutrition, Prevention and Health.
Vitamin A can be obtained in the diet from sources including liver, whole milk, cheese, carrots, dark green leafy vegetables, and orange-coloured fruits.
Vitamin E is found in vegetable oils, nuts and seeds.
Elsehwere, researchers from Queen Mary University of London are currently running a study to find out if correcting people’s vitamin D deficiencies over winter can reduce the risk and/or severity of Covid-19 and other acute respiratory infections.
Vitamin D deficiency is more common in older people, in people who are overweight, and in black and Asian people – all of the groups who are at increased risk of becoming very ill with Covid-19.
Lead researcher Professor Adrian Martineau, of Queen Mary University of London, said: “There is mounting evidence that vitamin D might reduce the risk of respiratory infections, with some recent studies suggesting that people with lower vitamin D levels may be more susceptible to coronavirus.”
In June, the National Institute for Health and Care Excellence (Nice) examined five studies on coronavirus and vitamin D and concluded that there is currently no evidence to support taking vitamin D supplements to reduce the risk or severity of Covid-19.