Every spring, when the allergy colds strikes, the sale of vitamin C supplements increases.  On every desk in a America you find supplements like emergen-c and citrus tea being guzzled by the gallons in an attempt to prevent or stave off the lurking cold.  But according to research,  you are going to get the cold whether or not you take Vitamin-C; however,  the studies show that when taken during a cold, vitamin c will reduce the length of time you are sick.  According to the review article, Vitamin C for preventing and treating the common cold,

“The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified, yet vitamin C may be useful for people exposed to brief periods of severe physical exercise. Regular supplementation trials have shown that vitamin C reduces the duration of colds, but this was not replicated in the few therapeutic trials that have been carried out. Nevertheless, given the consistent effect of vitamin C on the duration and severity of colds in the regular supplementation studies, and the low cost and safety, it may be worthwhile for common cold patients to test on an individual basis whether therapeutic vitamin C is beneficial for them. Further therapeutic RCTs are warranted.”

In conclusion,  we commonly think of vitamin C as preventative, when in reality getting the cold is inevitable.  However,  supplementation of vitamin C might be a good idea, in order to shorten the length of time you are sick.