How many studies support 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's backed by 9 published studies in Vitaebase's database, including 9 meta-analyses, the most recent from 2021 -- a fairly substantial body of research for a single topic.