Vitamin C for preventing and treating pneumonia

Background Pneumonia is one of the most common serious infections, causing two million deaths annually among young children in developing countries. In developed countries pneumonia is most significantly a problem of the elderly. Objectives To assess the prophylactic and therapeutic effects of vitamin C on pneumonia. Search strategy We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2006, Issue 1), OLD MEDLINE (1950 TO 1965), MEDLINE (1966 to February Week 2, 2006), EMBASE (1974 toMarch 2006), Web of Science (1945 to February 2006) and reference lists of reviews and articles. Selection criteria To assess the therapeutic effects of vitamin C, we selected placebo-controlled trials. To assess prophylactic effects, we selected controlled trials with or without a placebo. Data collection and analysis Two review authors independently read the trial reports and extracted data. Main results We identified three prophylactic trials which recorded 37 cases of pneumonia in 2,335 people. Only one was satisfactorily randomised, double-blind and placebo-controlled. Two trials examined military recruits and the third studied boys from "lower wage-earning classes" attending a boarding school in the UK during World War II. Each of these trials found a statistically significant (80% or greater) reduction in pneumonia incidence in the vitamin C group. We identified two therapeutic trials involving 197 pneumonia patients. Only one was satisfactorily randomised, double-blind and placebo-controlled. One studied elderly patients in the UK which found lower mortality and reduced respiratory symptom scores in the vitamin C group; however, the benefit was restricted to the most ill patients. The other studied adults (with a wide age range) in the former Soviet Union and found a dose-dependent reduction in the time to recovery with two vitamin C doses. Authors' conclusions The prophylactic use of vitamin C to prevent pneumonia should be further investigated in populations who have high incidence of pneumonia, especially if dietary vitamin C intake is low. Similarly, the therapeutic effects of vitamin C should be studied especially in patients with low plasma vitamin C levels. The current evidence is too weak to advocate widespread prophylactic use of vitamin C to prevent pneumonia in the general population. However, therapeutic vitamin C supplementation may be reasonable for pneumonia patients who have low vitamin C plasma levels because its cost and risks are low.