Efficacy of vitamin C for the prevention and treatment of upper respiratory tract infection. A meta-analysis in children.

PURPOSE: Upper respiratory tract infection (URTI) is a common infection in children, generally caused by viral respiratory infection. Vitamin C is currently proposed as prophylaxis for URTI. The purpose of this study was to assess the effectiveness of vitamin C administration in children for the prevention and reduced duration of URTI through a systematic literature review. METHODS: Review of the literature conducted between October 2017 and January 2018 in the main medical databases (CENTRAL, Medline and Embase) and by a gray literature approach. The selection criteria were: double-blind randomized controlled trials (RCTs) comparing vitamin C use to placebo in children aged 3 months to 18 years without chronic infection. Efficacy was assessed in terms of incidence, duration and severity of symptoms of URTI. A meta-analysis was conducted where possible. RESULTS: Eight RCTs, including 3135 children aged 3 months to 18 years, were selected. Quantitative analysis showed no difference between vitamin C administration and placebo (odds ratio = 0.75, 95% CI [0.54-1.03], p = 0.07, I2 = 74%). Vitamin C administration was found to decrease the duration of URTI by 1.6 days (standardized mean differences = -0.30 [-0.53; -0.08], p = 0.009, I2 = 70%). Children under 6 years of age benefit from more effective vitamin C supplementation associated with echinacea. No serious adverse events were reported. CONCLUSIONS: Although no preventive effects were found, vitamin C intake reduced the duration of URTI. Considering the frequency of URTI, the inappropriate prescription of antibiotics, and the safe nature of vitamin C, its supplementation is justified, especially in children under 6 years of age and those who present a high frequency of URTI. There is a sound rationale for further trials with greater statistical power among children of this age.