Zinc and the common cold: a meta-analysis revisited.

The common cold has been estimated to cost the United States > $3.5 billion per year. Despite several randomized clinical trials, the effect of treating colds with zinc gluconate remains uncertain due to conflicting results. We conducted a meta-analysis of published randomized clinical trials on the use of zinc gluconate lozenges in colds using the random effects model of DerSimonians and Laird. Ten clinical trials of cold treatment with zinc gluconate were identified. After excluding two studies that used nasal inoculum of rhinovirus, eight trials were combined and analyzed. The summary odds ratio for the presence of "any cold symptoms" at 7 d was 0.52 (95% confidence interval, 0.25-1.2). We conclude that despite numerous randomized trials, the evidence for effectiveness of zinc lozenges in reducing the duration of common colds is still lacking.