Summary
This study, conducted by a Canadian University, investigated whether vitamin D supplementation could prevent viral upper respiratory tract infections. 600 participants were divided into four groups. 1st group: vitamin D and gargling; 2nd group: placebo and gargling; 3rd group: vitamin D only, and 4th group: placebo only. The results showed that vitamin D supplementation significantly reduced upper respiratory tract infections. It was suggested that supplementation additionally might reduce the risk of clinical infections. More details can be found in the study.
References
Goodall et al.