Vitamina C para la prevención y tratamiento de la neumonía

BACKGROUND: Pneumonia is one of the most common, serious infections, causing two million deaths annually among young children in low-income countries. In high-income countries pneumonia is most significantly a problem of the elderly. OBJECTIVES: To assess the prophylactic and therapeutic effects of vitamin C on pneumonia. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2011, Issue 1) which contains the Acute Respiratory Infections Group’s Specialised Register, MEDLINE (1950 to January week 4, 2011), EMBASE (1974 to February 2011) and Web of Science (1945 to February 2011). 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 2335 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. That trial studied elderly patients in the UK and 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 therapeutic trial 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.