The investigators will assess the relative impact of daily preventive zinc supplementation (7 mg zinc/d for one year), intermittent preventive supplementation (10 mg zinc/d for 10 days every three months for one year), and zinc treatment during episodes of diarrhea (20 mg zinc/d for 10 days beginning with each episode of diarrhea during one year). Outcomes that will be assessed include the incidence and duration of all episodes of diarrhea, the incidence of malaria, physical growth, and (in a sub-group) biochemical indicators of zinc, iron and vitamin A status.