Preventive zinc supplementation for children, and the effect of additional iron: a systematic review and meta-analysis

Preventive zinc supplementation for children, and the effect of additional iron: a systematic review and meta-analysis

Zinc deficiency is widespread, and preventive supplementation may have benefits in young children. Effects for children over 5 years of age, and effects when co-administered with other micronutrients are uncertain. These are obstacles to scale-up. This review seeks to determine if preventive supplementation reduces mortality and morbidity for children aged 6 months to 12 years.

In this review, 80 randomised trials with 205 401 participants are included and the results indicate that:

  • there is a small but non-significant effect on all-cause mortality (risk ratio (RR) 0.95 (95% CI 0.86 to 1.05))
  • supplementation may reduce incidence of all-cause diarrhoea (RR 0.87 (0.85 to 0.89)), but there is evidence of reporting bias
  • there is no evidence of an effect of incidence or prevalence of respiratory infections or malaria
  • there is moderate quality evidence of a very small effect on linear growth (standardised mean difference 0.09 (0.06 to 0.13)) and an increase in vomiting (RR 1.29 (1.14 to 1.46))
  • there is no evidence of an effect on iron status
  • comparing zinc with and without iron co-supplementation and direct comparisons of zinc plus iron versus zinc administered alone favours co-intervention for some outcomes and zinc alone for other outcomes
  • effects may be larger for children over 1 year of age, but most differences are not significant

The review concludes that benefits of preventive zinc supplementation may outweigh any potentially adverse effects in areas where risk of zinc deficiency is high. Further research should determine optimal intervention characteristics and delivery strategies.

[Adapted from author]