Based on the single study we have analyzed so far, our current analysis leans toward the idea that high dose vitamin C may help shorten the duration of the common cold. The evidence we reviewed suggests that taking at least 200 mg of vitamin C daily is associated with an 8% reduction in cold duration for adults and a 14% reduction for children [1]. Importantly, starting vitamin C supplementation after symptoms appear appears to be especially effective according to this study [1]. However, this finding comes from only one set of data, and we have not yet reviewed any conflicting evidence. Because our analysis is partial at this point, we cannot say how consistent this effect might be across different populations or whether vitamin C meaningfully reduces symptom severity. What we can report is that the available evidence, though limited, points toward a modest benefit for shortening colds rather than preventing them entirely. For practical purposes, if you choose to try vitamin C during a cold, the evidence we've reviewed supports taking at least 200 mg daily, and starting early in the illness may be most helpful. Keep in mind that this is our current interpretation based on a single supporting study, and future analyses may shift what we find.