Vitamin C for preventing and treating pneumonia.
Level 1 - systematic review of randomized trials
Cochrane systematic review of controlled and randomized trials
PubMed 23925826 · doi:10.1002/14651858.CD005532.pub3
What was done
This Cochrane systematic review evaluated controlled trials examining vitamin C for preventing or treating pneumonia. Searches were conducted across CENTRAL, MEDLINE, EMBASE, and Web of Science through April 2013. Two authors independently selected trials and extracted data, evaluating placebo-controlled trials for therapeutic effects and controlled trials with or without placebo for prophylactic effects.
What was found
Six trials were identified across several indications: - Prophylaxis (community-acquired pneumonia): 3 trials (2,335 participants, 37 pneumonia cases) in military recruits and WWII UK boarding school boys. Each reported an 80% or greater statistically significant reduction in pneumonia incidence with vitamin C; only 1 trial was adequately randomized, double-blind, and placebo-controlled. - Prophylaxis (hospital-acquired pneumonia): 1 trial in 37 severely burned patients (13 cases) found a 1-day administration of vitamin C had no effect on pneumonia incidence. - Treatment: 2 trials (197 patients). One randomized, double-blind, placebo-controlled trial in elderly UK patients found lower mortality and reduced severity in the vitamin C group, restricted to the most severely ill patients. A second trial in the former Soviet Union found a dose-dependent reduction in pneumonia duration with two vitamin C doses. - Adverse effects: None were reported in the included studies.
Why it matters
Vitamin C supplementation shows potential prophylactic benefit in specific high-incidence or deficient groups and therapeutic benefit in severely ill patients, but the current evidence is too weak and heterogeneous to support general population prophylaxis.
Limits
The total evidence base is small (6 trials total, only 197 therapeutic patients) and clinically heterogeneous. Only 2 of the 6 trials met rigorous methodological standards (satisfactorily randomized, double-blind, and placebo-controlled). Prophylactic populations were limited to historical cohorts (WWII schoolboys, military recruits, burn patients), limiting generalizability to modern general populations.
Cited by
- supports Three randomized controlled trials investigating vitamin C as a prophylactic treatment against pneumonia each found an 80% lower incidence of pneumonia in people taking vitamin C compared to controls.