Vitamin C, zinc and the common cold
When you start to get symptoms of a cold, do you rush to the store to stock up on vitamin C supplements and zinc lozenges? You might be better off saving your money. Here is a summary of the evidence:
Supplementing with high doses of vitamin C after the onset of cold symptoms showed no consistent effect on the duration or severity of the common cold.
However, taking vitamin C regularly as a preventative measure had no effect on the incidence of the common cold in the ordinary population, but it had a small, but consistent effect in reducing the duration and severity of cold symptoms. Interestingly, regular vitamin C consumption reduced the risk of catching a cold in those exposed to short periods of extreme physical stress (such as marathon runners and skiers) by half.
Despite numerous clinical trials, there is no consistent evidence that zinc lozenges affect the duration or severity of the common cold.
Hemilä H, Chalker E, Douglas B. (2007). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, Issue 3. Art. No.: CD000980. DOI: 10.1002/14651858.CD000980.pub3.
Jackson, J.L, Lesho, E. & Peterson, C. (2000). Zinc and the common cold: a meta-analysis revisited. Journal of Nutrition, 130(5): 1512S-1515S.