Resumen
Breast-fed infants can thrive even under unhygienic conditions in areas of extreme poverty. The anti-infectious properties of human milk account for the very high resistance of the nursing infant to infection in general and in particular to diarrhea. In deprived tropical environments, most infants grow adequately, even if they have experienced fetal growth retardation or were born prematurely, as long as they are kept at the breast during the first 4 to 6 months of life. Breast milk has unique immunologic, nutritional, psychosocial, and economic benefits, and efforts should continue to promote breast-feeding in all societies.