Role of Vitamin D in acute respiratory infections

Vitamin D supplements protect against acute respiratory infections including colds and flu, according to a study led by the Queen Mary University of London.

The study provides the most robust evidence yet that vitamin D has benefits beyond bone and muscle health, and could have major implications for public health policy, including the fortification of foods with vitamin D to tackle high levels of deficiency in the UK. The results, published in the BMJ, are based on a new analysis of raw data from around 11,000 participants in 25 clinical trials conducted in 14 countries including the UK, USA, Japan, India, Afghanistan, Belgium, Italy, Australia and Canada.

Individually, these trials yielded conflicting results, with some reporting that vitamin D protected against respiratory infections, and others showing no effect.

Lead researcher Professor Adrian Martineau from Queen Mary University of London said: “This major collaborative research effort has yielded the first definitive evidence that vitamin D really does protect against respiratory infections. Our analysis of pooled raw data from each of the 10,933 trial participants allowed us to address the thorny question of why vitamin D ‘worked’ in some trials, but not in others.”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.” Vitamin D – the ‘sunshine vitamin’ – is thought to protect against respiratory infections by boosting levels of antimicrobial peptides – natural antibiotic-like substances – in the lungs.

Overall, the reduction in risk of acute respiratory infection induced by vitamin D was on a par with the protective effect of injectable ‘flu vaccine against ‘flu-like illnesses. Vitamin D supplementation is safe and inexpensive, so reductions in acute respiratory infections brought about by vitamin D supplementation could be highly cost-effective.

Citation: Martineau, Adrian R., David A. Jolliffe, Richard L. Hooper, Lauren Greenberg, John F. Aloia, Peter Bergman, Gal Dubnov-Raz, Susanna Esposito, Davaasambuu Ganmaa, Adit A. Ginde, Emma C. Goodall, Cameron C. Grant, Christopher J. Griffiths, Wim Janssens, Ilkka Laaksi, Semira Manaseki-Holland, David Mauger, David R. Murdoch, Rachel Neale, Judy R. Rees, Steve Simpson, Iwona Stelmach, Geeta Trilok Kumar, Mitsuyoshi Urashima, and Carlos A. Camargo. “Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.” Bmj, 2017, I6583. doi:10.1136/bmj.i6583.
Adapted from press release by the Queen Mary University of London.