More than three million people across the UK could stave off infections such as colds or flu every year if everyone took Vitamin D supplements, experts have said.
A new study has found that taking the supplements protects against acute respiratory infections.
Vitamin D supplements have been a hot topic in medical circles in recent years with some experts arguing that their usefulness remains uncertain.
But health officials say that vitamin D is vital for bone and muscle health.
Last year, Public Health England said that people were generally not getting the recommended 10 micrograms of vitamin D a day from sunlight in winter.
The latest new study, published in The British Medical Journal, suggests that taking vitamin D – also known as the sunshine vitamin – may have benefits beyond bone and muscle health and protects against acute respiratory infections.
Results of the study fit with the observation that colds and flu are most common during winter and spring, when levels of vitamin D are at their lowest.
Respiratory tract infections are any infection of the sinuses, throat, airways or lungs and can last up to 30 days.
The common cold is the most widespread respiratory tract infection; others include ear infections, bronchitis and pneumonia.
At least 70% of the population gets at least one acute respiratory infection every year. And about a quarter of the UK population will visit the GP each year to get treatment.
Acute respiratory infections lead to 300,000 hospital admissions and they lead to 35,000 deaths across the UK every year.
The new research, led by academics from Queen Mary University of London (QMUL), analysed data from almost 11,000 participants aged up to 95 who took part in 25 clinical trials conducted in 14 countries, including the UK.
The study concluded that supplements can help prevent acute respiratory tract infections, particularly among those who are deficient in vitamin D.
After adjusting for other potentially influential factors, the researchers found that vitamin D supplementation cut the proportion of participants experiencing at least one acute respiratory tract infection by 12%.
Lead researcher Professor Adrian Martineau, from QMUL, said: “Assuming a UK population of 65 million, and that 70% have at least one acute respiratory infection each year, then daily or weekly vitamin D supplements will mean 3.25 million fewer people would get at least one acute respiratory infection a year.”
Experts said that the study had implications for public health policy, including the possibility of fortification of foods with vitamin D to tackle high levels of deficiency in the UK.
Professor Martineau added: “The bottom line is that the protective effects of vitamin D supplementation are strongest in those who have the lowest vitamin D levels and when supplementation is given daily or weekly rather than in more widely spaced doses.
“Vitamin D fortification of foods provides a steady, low-level intake of vitamin D that has virtually eliminated profound vitamin D deficiency in several countries.
“By demonstrating this new benefit of vitamin D, our study strengthens the case for introducing food fortification to improve vitamin D levels in countries such as the UK where profound vitamin D deficiency is common.”
But in a linked editorial, other experts suggest that evidence does not support the use of vitamin D supplementation to prevent disease “except for those at high risk of osteomalacia”.
Commenting on the latest study, Professor Louis Levy, head of nutrition science at Public Health England, said: “Based on evidence reviewed by the Scientific Advisory Committee on Nutrition (SACN), we recommend that certain population groups take a daily 10 micrograms vitamin D supplement year round and everyone considers taking one during the autumn and winter months to protect musculoskeletal health.
“The evidence on vitamin D and infection is inconsistent and this study does not provide sufficient evidence to support recommending vitamin D for reducing the risk of respiratory tract infections.”