Does breast feeding help protect against atopic disease? Biology, methodology, and a golden jubilee of controversy.

To help shed some light on the 50-year-old controversy concerning the possible protective effect of breast feeding on subsequent atopic disease, I developed 12 standards pertaining to both biologic and methodologic aspects of exposure (infant feeding), outcome (atopic conditions), and statistical analysis for studies of atopic eczema, asthma, allergic rhinitis, cow milk allergy, and other food allergy. Among the published studies on atopic eczema, the nine claiming a protective benefit of breast feeding performed less well than the 12 not making such a claim on "methodologic" standards relating to strict diagnostic criteria and blind ascertainment of outcome. The positive studies were somewhat stronger, however, on the "biologic" standards bearing on sufficient duration and exclusivity of breast feeding and on separate analysis of children at high risk. For the other atopic conditions, there were no important differences between positive and negative studies. In few negative or positive studies was there adequate control for confounding variables or examination of potential benefits relating to the severity or age at onset of atopic disease. To avoid another 50 years of unresolved controversy, future studies should improve both the biologic and methodologic aspects of their design and analysis.