Vitamin C for preventing and treating pneumonia.

Systematic review of clinical trials assessing vitamin C for preventing and treating pneumonia in community and hospital settings. Included populations ranged from teenage boarding school boys and military recruits to hospitalized elderly adults with acute respiratory infections, patients with pneumonia, and severely burned intensive care patients.

Vitamin C was evaluated as both prophylaxis and treatment for pneumonia across multiple trials, given orally as pills or powder, added to milk or cocoa, or administered intravenously. Doses varied widely across studies, including 0.2 g/day, 2 g/day, 50 to 100 mg per 100,000 antibiotic units for 10 days, and high-dose intravenous vitamin C 66 mg/kg/h for 24 hours; some prophylaxis trials did not report the exact dose.

Overall, vitamin C showed possible benefit in some prevention and treatment settings, but results were inconsistent and not strong enough to support routine use for the general population. In prophylaxis trials, pneumonia incidence was 0/335 versus 17/1100 in Glazebrook 1942, 2/114 versus 10/112 in Kimbarowski 1967, and 1/331 versus 7/343 in Pitt 1979, while hospital-acquired pneumonia prevention in Tanaka 2000 showed no clear benefit (7/19 vs 6/18). In Hunt 1994, the most severely ill subgroup had improved respiratory score change with vitamin C versus placebo, -2.38 (95% CI -4.32, -0.44), but the less ill subgroup did not (-0.04, 95% CI -1.15, 1.07); mortality was 1/28 versus 5/29 (OR 0.24, 95% CI 0.04 to 1.29). Mochalkin 1970 also suggested shorter hospital stay with higher vitamin C dose, 23.7 days in control, 19.1 days in low C, and 15.1 days in high C.

The evidence base was small, old, and clinically heterogeneous, with major variation in populations, pneumonia setting, dose, route, and outcome definitions. Several trials had limited reporting of methods and dosing, and the findings were inconsistent across prophylactic and therapeutic settings. Results are therefore indirect and not sufficient to establish routine prophylaxis or treatment for all patients.