In the UK, an international research team led by Queen Mary University of London found that vitamin D supplements protect against acute respiratory infections including colds and flu, on a par with the protective effect of injectable flu vaccines. Vitamin D supplementation is safe and inexpensive, so reductions in acute respiratory infections brought about by vitamin D supplementation could be highly cost-effective.
Known as the sunshine vitamin and already linked to benefiting bone and muscle health, vitamin D protects against respiratory infections by boosting levels of antimicrobial peptides – natural antibiotic-like substances – in the lungs.
Daily or weekly supplementation halved the acute respiratory infection risk in people with the lowest baseline vitamin D levels. People with higher baseline vitamin D levels also benefited with about a 10 percent reduction. Results fit with the observation that colds and flu are prevalent in winter and spring, when levels of vitamin D are lowest.