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Young children living in the southern plains of Nepal are often deficient in zinc. Replacing it had no effect on mortality or infectious illnesses in a large cluster randomised trial, howeverhowever.. More than 20000 children aged 1-35 months took tablets containing zinc or a placebo for up to three years. Overall rates of death were about the same in each group (316 v 333 deaths; hazard ratio 0.92, 95% CI 0.75 to 1.12). Diarrhoea, dysentery, and respiratory infections were the most common causes of death. The authors found a suggestion that zinc might reduce mortality in children over 12 months, but the result was not significant (0.80, 0.60 to 1.06). Zinc supplements had no effect on the risk of diarrhoea, dysentery, or respiratory illness in a linked substudy.
Disappointed by their equivocal results, the authors pooled their data with three other large trials from South Asia and Africa. The analysis confirmed their negative findings on overall mortality, but the extra power turned the hint of benefit for older children into a statistically significant result (0.82, 0.70 to 0.96).
It seems likely that extra zinc helps at least some children in some regions, says a linked comment (p 1194). But it is too early to recommend universal supplementation.