Twelve studies were included in the review. The total number of participants was unstated. Ten studies were individually randomised trials and two were cluster-randomised trials. All studies had adequate allocation concealment and all used intention-to-treat analysis. There was between 0.9% and 7.3% loss to follow-up.
Four trials, when pooled, showed a benefit of zinc for all-cause mortality (RR 46%, 95% CI 12% to 68%). Two trials, when pooled, showed a benefit of zinc for diarrhoea hospitalisations (RR 23%, 95% CI 15% to 31%). Other outcomes were not statistically significant.
After application of CHERG rules and using diarrhoea hospitalisations as the closest and most conservative possible proxy for diarrhoea mortality, zinc treatment for diarrhoea was estimated to decrease diarrhoea mortality by 23% (two studies).