http://www.findarticles.com/p/articles/ ... i_n9469932
http://www.ingentaconnect.com/content/a ... 1/art00026
Vitamin C Supplementation and Respiratory Infections - a Systematic Review
Eight of these trials were double blind and placebo controlled and seven were randomized. Five small trials found a statistically significant 45 to 91% reduction in common cold incidence in the vitamin C group. These trials were short and the participants were under heavy exertion during the trial. Furthermore, three other trials found a statistically significant 80 to 100% reduction in the incidence of pneumonia in the vitamin C group.