In a recent meta-analysis, Hemilä and Louhiala analyzed the effect of vitamin C in preventing and treating pneumonia regardless of the etiology [65]. They reported three studies that show a >80% lower incidence of pneumonia in the vitamin C groups, supporting the potential role of vitamin C in reducing the risk of pneumonia, particularly in individuals with low plasma vitamin C levels [66]. Furthermore, regarding the effect of vitamin C in treating pneumonia, in older patients, lower mortality and reduced severity of disease was found in the vitamin C group, particularly in the most ill patients. However, the authors concluded that the current evidence is too weak to advocate widespread prophylactic use of vitamin C to prevent pneumonia in the general population, and further studies are needed to clarify the population that could have a benefit from vitamin C use. The effect of vitamin C on upper respiratory tract infections, such as the common cold, has also been studied in several trials. Vitamin C supplementation significantly decreases the incidence and the severity of the common cold in people under heavy physical stress [67,68]. In a randomised controlled pilot study, Garaiova et al. have shown a significant reduction in the incidence and duration of upper respiratory tract infection, but no significant differences were observed in the incidence rate ratio or duration of lower respiratory tract infection [69]. A recent meta-analysis comparing vitamin C with placebo demonstrated that administration of extra doses of vitamin C at the onset of a common cold could help reduce the duration by about half a day, shorten the time confined indoors, and relieve the symptoms of a common cold [70].