Global Study: Vitamin D Protects Against Colds and Flu
FARS News Agency
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
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
Lead researcher Professor
"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
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 liter (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