How strong is the evidence for Vitamin C?

A well-known Cochrane review found that regular vitamin C supplementation does not reduce the incidence of the common cold in the general population, though it modestly shortens cold duration and severity — a nuance later confirmed by dedicated meta-analyses of supplementary and higher-dose regimens. That evidence is currently rated emerging (35/100), built on 9 published studies, including 9 meta-analyses -- still too little to draw firm conclusions from.