Abstract 

Objective: This meta-analysis examines the effects of vitamin C supplementation on plasma vitamin C levels and common cold duration and severity.

Context: Vitamin C is essential for immune function. Supplementation may reduce cold incidence and symptoms. However, placebo-controlled trials show inconsistent benefits.

Methods Used: A systematic review and meta-analysis of 13 randomized controlled trials with 9745 common cold episodes. Plasma vitamin C and duration/severity of colds were pooled across studies.

Researchers' Summary of Findings: Vitamin C supplementation increased plasma vitamin C levels. It did not significantly affect common cold duration but reduced severity by 8% compared to placebo.

Health Implications: Vitamin C supplementation boosts circulating levels. It may have modest benefits on common cold severity but does not appear to reduce duration. Further research is needed on optimal dosing strategies.

DOI: 10.1093/ajcn/71.6.1480