Vitamin D supplements protect against acute respiratory infections including colds and flu, according to a study led by Queen Mary University of London (QMUL).
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 QMUL 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. Results of the study fit with the observation that colds and 'flu are commonest in winter and spring, when levels of vitamin D are at their lowest. They may also explain why vitamin D protects against asthma attacks, which are commonly triggered by respiratory viruses.
Daily or weekly supplementation halved the risk of acute respiratory infection in people with the lowest baseline vitamin D levels, below 25 nanomoles per litre (nmol/L). However, people with higher baseline vitamin D levels also benefited, although the effect was more modest (10 per cent risk reduction). 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.
Acute respiratory infections are a major cause of global morbidity and mortality. Upper respiratory infections such as colds and 'flu are the commonest reason for GP consultations and days off work. Acute lower respiratory infections such as pneumonia are less common, but caused an estimated 2.65 million deaths worldwide in 2013. Vitamin D supplementation is safe and inexpensive, so reductions in acute respiratory infections brought about by vitamin D supplementation could be highly cost-effective.
The study was conducted by a consortium of 25 investigators from 21 institutions worldwide* and funded by the National Institute for Health Research.
For more information, please contact:
Joel Winston, Public Relations Manager (School of Medicine and Dentistry)
Queen Mary University of London
Tel: +44 (0)20 7882 7943 / +44 (0)7970 096 188
Notes to the editor
* Institutions involved in the research: Edmond and Lily Safra Children's Hospital (Tel Hashomer, Israel), Geisel School of Medicine at Dartmouth (NH, USA), Harvard School of Public Health (Boston, MA, USA), Jikei University School of Medicine (Tokyo, Japan), Karolinska Institutet (Stockholm, Sweden), Massachusetts General Hospital (Boston, MA, USA), McMaster University (Hamilton, Ontario, Canada), Medical University of Lodz (Poland), QIMR Berghofer Medical Research Institute (Queensland, Australia), Queen Mary University of London (UK), The Pennsylvania State University (Hershey, PA, USA), Università degli Studi di Milano (Milan, Italy), Universitair ziekenhuis Leuven (Belgium), University of Auckland (New Zealand), University of Birmingham (UK), University of Colorado School of Medicine (Aurora, CO, USA), University of Delhi (India), University of Otago (Christchurch, New Zealand), University of Tampere (Finland), University of Tasmania (Australia), Winthrop University Hospital (Mineola, NY, USA).
Research paper: 'Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of individual participant data'. Martineau et al. BMJ 2017
Link once embargo lifts: http://www.bmj.com/cgi/doi/10.1136/bmj.i6583
About Queen Mary University of London
Queen Mary University of London (QMUL) is one of the UK's leading universities, and one of the largest institutions in the University of London, with 23,120 students from more than 155 countries.
A member of the Russell Group, we work across the humanities and social sciences, medicine and dentistry, and science and engineering, with inspirational teaching directly informed by our research. In the most recent national assessment of the quality of research, we were placed ninth in the UK (REF 2014).
As well as our main site at Mile End - which is home to one of the largest self-contained residential campuses in London - we have campuses at Whitechapel, Charterhouse Square, and West Smithfield dedicated to the study of medicine, and a base for legal studies at Lincoln's Inn Fields.
We have a rich history in London with roots in Europe's first public hospital, St Barts; England's first medical school, The London; one of the first colleges to provide higher education to women, Westfield College; and the Victorian philanthropic project, the People's Palace at Mile End.
Today, as well as retaining these close connections to our local community, we are known for our international collaborations in both teaching and research.
QMUL has an annual turnover of £350m, a research income worth £125m (2014/15), and generates employment and output worth £700m to the UK economy each year.
About National Institute for Health Research
The National Institute for Health Research (NIHR) is funded by the Department of Health to improve the health and wealth of the nation through research. The NIHR is the research arm of the NHS. Since its establishment in April 2006, the NIHR has transformed research in the NHS. It has increased the volume of applied health research for the benefit of patients and the public, driven faster translation of basic science discoveries into tangible benefits for patients and the economy, and developed and supported the people who conduct and contribute to applied health research. The NIHR plays a key role in the Government's strategy for economic growth, attracting investment by the life-sciences industries through its world-class infrastructure for health research. Together, the NIHR people, programmes, centres of excellence and systems represent the most integrated health research system in the world. For further information, visit the NIHR website (http://www.nihr.ac.uk).