Vitamin C

Research summary

• 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.
• For cardiovascular outcomes, prospective-study meta-analyses link higher vitamin C intake and circulating levels to lower stroke risk, and a GRADE-assessed meta-analysis found modest improvements in glycemic control and cardiovascular risk factors in people with type 2 diabetes, though a specific trial-level meta-analysis on preventing atrial fibrillation in high-risk patients found supportive but limited evidence.
• Broader dose-response meta-analyses of dietary antioxidants (including vitamin C) show associations with lower all-cause mortality, but these are observational and cannot isolate vitamin C's individual contribution.
• Overall, vitamin C's most commonly assumed benefit — cold prevention — is not supported by the evidence, while its more modest, specific benefits are real but limited.