Different studies reported a reduced incidence of respiratory infections in the zinc receiving group [269,271,272,273,280]. In 2007, Sazawal et al. reported a slight reduction in the relative risk of all-cause mortality in children supplemented with zinc in Zanzibar [277]. Other studies found instead that zinc supplementation had no significant effect on the frequency of respiratory infections [274,275,276,278,279,281]. Some of these trials used a lower daily dose of zinc, which might be one of the reasons why the supplementation was less effective; however, both negative and positive results were reported with different zinc dosages, from 5 up to 30 mg/day.