Vitamin D supplements ‘can prevent colds and flu’
Vitamin D supplements can protect against colds and flu, new research finds.
In a study led by Queen Mary University of London (QMUL), researchers have found the most clear evidence yet that vitamin D, known as the “sunshine vitamin”, has benefits beyond bone and muscle health. Analysing raw data from around 11,000 participants in 25 clinical trials conducted in 14 countries including the U.K., U.S., Japan, India, Afghanistan, Belgium, Italy, Australia and Canada, the researchers found that each study gathered conflicting results, with some reporting that vitamin D protected against respiratory infections, and others showing no effect.
However, the results fit with the observation that colds and flu are most common in winter and spring, when levels of vitamin D are at their lowest. Lead researcher Professor Adrian Martineau said that the research effort offers up the first definitive evidence that vitamin D really does protect against respiratory infections.
"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,” he said.
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).
But people with higher baseline vitamin D levels also benefited, although the effect was more modest, equalling a 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’.
Professor Martineau added that the study results could have major implications for public health policy, and suggests health agencies may want to look into the fortification of foods with vitamin D to tackle high levels of deficiency in the U.K.
"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,” he explained. “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 U.K. where profound vitamin D deficiency is common."