This review examines the available studies bearing on the relation between infant-feeding mode and infectious illness in the populations of less-developed countries.
A companion critical review of studies of the relationship of infant-feeding methods and infection in industrialized countries has concluded that, although laboratory studies provide biologic plausibility for a lower infection rate in breast-fed infants, an effect, if present, is apparently modest.39 The strongest evidence for a protective effect of breast-feeding in industrialized countries is for gastrointestinal (diarrheal) illness. In this review of studies among populations in developing countries we found the evidence for an important protective effect of breast-feeding against infectious illness to be much stronger. This conclusion was reached despite serious problems in the design of many of the studies reviewed.
One characteristic that distinguishes populations in less-developed countries from those of industrialized ones is the infant mortality. Even today, infant mortality for much of the world is up to ten times higher than infant mortality in the United States and Northern Europe.46 This undoubtedly reflects differences in sanitation, nutrition, housing, and other indicators of socioeconomic status. Much of the difference in rates of infant and child mortality and morbidity is attributable to high rates of infectious illness, especially gastrointestinal disease. Thus, in these populations, the positive effects of breast-feeding are of greater potential importance for the health of the infant population and should be easier to detect in clinical and epidemiologic studies.
In this review we will address the following key questions: (1) whether the method of infant feeding (breast v other) is associated with differences in rates of mortality, both overall and infectious, and in rates of infectious morbidity in less-developed countries;