OBJECTIVE: to identify the protective elements of breast milk that work in the prevention of gastrointestinal and respiratory diseases. SOURCES: the search was performed on Bireme, Lilacs, Medline and Scielo databases, using keywords breast milk, gastrointestinal disease and respiratory disease, with limits of languages (English, Portuguese and Spanish) and period (1996 to 2009). 46 papers were selected for achieving the objectives of this work. SUMMARY OF THE FINDINGS: the IgA is the immunoglobulin with more protective capability against both types of disease, to survive the intestinal and respiratory mucosa. Breast milk also contains other immunoglobulins, antibodies, oligosaccharides, lipids, bioactive peptides, among other components with unique mechanisms that besides the protection against these diseases, stimulate the development of infants' immune systems. No other milk has these properties, and may even be the cause of these diseases. Campaigns and actions in Public Health to encourage breastfeeding should be continuously developed and encouraged considering all the benefits it provides.