The effect of zinc supplementation to avoid childhood diarrhea and respiratory infections is still unclear. A meta-analysis of randomized controlled trials was conducted regarding the supplementation of zinc.

Randomized controlled trials of zinc supplementation for above or equal to 3 months for children less than 5 years of age using blinded assessment were identified through Science Citation Index, PubMed, and the Cochrane Database of Controlled Trials. The outcome measures included number of episodes of complaint, number of days with ailment, and number of episodes of severe illness. Data from 17 studies were assembled by using random-effects and fixed-effects models for data with and without substantial heterogeneity, respectively.

Children who had received a zinc supplement had less episodes of diarrhea and respiratory tract infections. The supplementation of zinc was associated with considerably fewer attacks of severe diarrhea or dysentery, persistent diarrhea and pneumonia or lower respiratory tract infection than placebo. Children receiving zinc supplement also had significantly fewer total days with diarrhea but not days with respiratory illness. Published studies indicated a publication bias and substantial heterogeneity but no cause could be identified.

The meta-analysis concluded that zinc supplementation can significantly reduce the frequency along with severity of diarrhea and respiratory illnesses and also the duration of diarrheal morbidity.

Source: Aggarwal R, Sentz J, Miller MA. Role of zinc administration in prevention of childhood diarrhea and respiratory illnesses: a meta-analysis. Pediatrics. 2007;119(6):1120-1130. doi:10.1542/peds.2006-3481