You have heard it time and time again. Take vitamin C to get over your cold quicker, or maybe even take vitamin C to prevent a cold.
While Vitamin C has other health benefits, it will not help you avoid colds or minimize the impact of a cold. Over the past 40 years, numerous epidemiological and placebo-controlled trials have examined the effect of Vitamin C supplementation on the prevention and treatment of colds. More than 30 clinical trials with over 10,000 participants have examined the effects of taking daily vitamin C in doses up to 2 g/day. The majority of studies of non-athletic people, when looked at collectively, led researchers to conclude that vitamin C does not prevent or treat the common cold, but highly physically active people training in stressful conditions (e.g. soldiers training in the Arctic) may benefit from supplementation. Vitamin C does not prevent a cold or affect symptom severity.
Claims of vitamin C’s efficacy in treating the common cold have been criticized by many researchers. The most-cited reviews of the subject have concluded that there are no beneficial effects beyond a placebo. A review of 72 studies, published in January 2013, found no significant effect of consuming vitamin C supplementation on the incidence of colds.