Although vitamin C has typically hogged the limelight as the great cold and flu defender, it appears vitamin D may also play a keen role in fighting winter illness.
Findings published in the Archives of Internal Medicine from the University of Colorado showed that vitamin D plays a critical role in immune function.
The study examined 19,000 people, concluding that low intake of vitamin D resulted in a significantly lower ability to ward off respiratory illnesses such as cold and flu.
Lead author Adit Ginde believes the results could be due to vitamin D's role in the production of a proteins called cathelicidins found in microphage cells (amongst others), which themselves play a role in immunity.
"While it's too early to make any definitive recommendations, many Americans also need more vitamin D for its bone and general health benefits," says Ginde.