A 2017 systematic review and meta-analysis found that vitamin D supplements may help to prevent colds and flu in as many as 3 million people every year.
This large-scale research, published in the British Medical Journal, reviewed 25 randomised controlled trials, and analysed data from a total of 11,213 participants. Results showed that daily or weekly vitamin D supplements could mean 3 million fewer people experiencing at least one acute respiratory tract infection each year.
Vitamin D plays a role in the immune system, by helping to induce antimicrobial peptides, which help to fight bacteria and viruses. However, because vitamin D is made in the skin in response to sunlight, many people have low levels in the winter.
Whilst Public Health England recommends that everyone in the UK take a daily supplement of vitamin D between October and March, and that higher risk groups such as babies and young children up to the age of 4, should supplement all year round, these recommendations are based on muscle and bone health primarily.
This new analysis shows that vitamin D is not only vital for healthy bones, but your immune system too.
The analysis showed that those with a vitamin D deficiency experienced the greatest clinical benefits, and that daily or weekly doses had a protective effect against acute respiratory tract infections, whereas large super-doses did not.
Respiratory tract infections (which range from the common cold to pneumonia) are responsible for hundreds of thousands of hospital admissions every year, and thousands of deaths, so the results of this study, showing that vitamin D supplements could help to prevent such infections, especially in those who are vitamin D deficient are incredibly significant.
Martineau A et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. British Medical Journal 2017; 356:i6583