This systematic review and meta-analysis was conducted to evaluate the efficacy and safety of zinc for the treatment of the common cold. Electronic databases and other sources for studies published through to September 2011 were searched and 17 randomized controlled trials comparing orally administered zinc with placebo or no treatment were included (N = 2,121). Compared to placebo, subjects receiving zinc had a shorter duration of cold symptoms (mean difference -1.65 days; 95% CI -2.50 to -0.81); however, heterogeneity was high (I2 = 95%). Zinc shortened the duration of cold symptoms in adults (mean difference -2.63; 95% CI -3.69 to -1.58), but no significant effect was seen among children (mean difference -0.26; 95% CI -0.78 to 0.25). Heterogeneity remained high in all subgroup analyses, including by age, dose of ionized zinc, and zinc formulation. The occurrence of adverse events (RR 1.24; 95% CI 1.05-1.46), bad taste (RR 1.65; 95% CI 1.27-2.16), and nausea (RR 1.64; 95% CI 1.19-2.27) were more common in the zinc group than in the placebo group. Therefore, oral zinc formulations may shorten the duration of common cold symptoms but large high-quality trials are needed before definitive recommendations can be made. CMAJ. 2012 May 7. PMID: 22566526
