title: Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials.
abstract: BACKGROUND
  Results of randomized controlled trials evaluating zinc for the treatment of the common cold are conflicting. We conducted a systematic review and meta-analysis to evaluate the efficacy and safety of zinc for such use.
  
  
  METHODS
  We searched electronic databases and other sources for studies published through to Sept. 30, 2011. We included all randomized controlled trials comparing orally administered zinc with placebo or no treatment. Assessment for study inclusion, data extraction and risk-of-bias analyses were performed in duplicate. We conducted meta-analyses using a random-effects model.
  
  
  RESULTS
  We included 17 trials involving a total of 2121 participants. Compared with patients given placebo, those receiving zinc had a shorter duration of cold symptoms (mean difference -1.65 days, 95% confidence interval [CI] -2.50 to -0.81); however, heterogeneity was high (I(2) = 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 any adverse event (risk ratio [RR] 1.24, 95% CI 1.05 to 1.46), bad taste (RR 1.65, 95% CI 1.27 to 2.16) and nausea (RR 1.64, 95% CI 1.19 to 2.27) were more common in the zinc group than in the placebo group.
  
  
  CONCLUSIONS
  The results of our meta-analysis showed that oral zinc formulations may shorten the duration of symptoms of the common cold. However, large high-quality trials are needed before definitive recommendations for clinical practice can be made. Adverse effects were common and should be the point of future study, because a good safety and tolerance profile is essential when treating this generally mild illness.
authors.affiliation: Division of Infectious Diseases, The Hospital for Sick Children, Toronto, Ont. michelle.science@sickkids.ca
authors.forename: Michelle
authors.initials: M
authors.lastname: Science
authors.forename: Jennie
authors.initials: J
authors.lastname: Johnstone
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Roth
authors.forename: Gordon
authors.initials: G
authors.lastname: Guyatt
authors.forename: Mark
authors.initials: M
authors.lastname: Loeb
mesh_terms: D000284:Administration, Oral; D003139:Common Cold / Q000188:drug therapy*; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D013997:Time Factors; D014131:Trace Elements / Q000627:therapeutic use*; D016896:Treatment Outcome; D015032:Zinc / Q000627:therapeutic use*
chemical_list: D014131:Trace Elements; D015032:Zinc