Zinc deficiency is widespread in developing countries and is recognized to impair growth and immune function [4]. Andean areas are included in the regions with the highest risk of zinc deficiency worldwide [5]. In Ecuador, 33% of children suffer from zinc deficiency. However, on the coast of Ecuador, where Guayaquil is located, the prevalence of zinc deficiency is 37% based on plasma zinc concentration below 70 micrograms/dl [6]. Stunting, which may result from chronic zinc undernutrition is present in 21.9% of children in Guayaquil [7]. In addition, in a previous study, we reported low dietary zinc intake in children from 12 to 59 months [8]. In urban areas of Ecuador, breast-feeding is not widely practiced, which could put very young children at risk of zinc deficiency [9]. Zinc is considered the most abundant intracellular micronutrient that participates in a wide range of cellular processes and plays a central role in the immune response to pathogens [10]. We previously demonstrated that zinc supplementation in Ecuadorian children caused an increased response to delayed type hypersensitivity tests to multiple pathogen-derived antigens [8].