It remains unclear whether breast-feeding protects infants against acute respiratory infection (ARI). To determine if breast-feeding protects against ARI as it does against diarrhea, 170 healthy newborns were followed for 6 mo. Feeding mode, incidence and duration of ARI and diarrhea were recorded biweekly. Infants were classified as fully or partially breast-fed, or formula-fed. Incidence and prevalence were computed monthly. The effects of duration of breast-feeding and potential confounders were analyzed by multiple and logistic regression analyses. Incidence and prevalence of ARI were significantly lower in fully breast-fed infants than in formula-fed infants from birth up to 4 mo, as was the mean duration of individual episodes (5.1 +/- 3.5 vs. 6.4 +/- 3.6 d, respectively). Incidence of ARI was negatively associated with duration of breast-feeding and positively associated with the presence of siblings (P < 0.05). The prevalence of ARI was associated only with the duration of breast-feeding (P < 0.05). Infants that were never breast-fed and that had one or more siblings were more likely to have an episode of ARI than those fully breast-fed for at least 1 mo. Incidence, prevalence, and duration of individual episodes of diarrhea were also lower in breast-fed infants. Incidence (r = -0.17, P < 0.02) and prevalence (r = -0.19, P < 0.008) were negatively associated with duration of full breast-feeding. Introduction of solid food was not associated with further episodes of diarrhea. The present results demonstrate protection against ARI as a result of breast-feeding similar to that for diarrhea, i.e., lower incidence and percentage of days ill, and episodes of shorter duration.

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This study was designed to test whether breast-feeding protects infants reared in unfavorable environments from growth-stunting by averting acute infections. The body weight and length, feeding mode and morbidity of 170 healthy infants were assessed at 15-d intervals from birth to 6 mo. Birth weight and length were not different between groups, but at 6 mo, breast-fed infants were heavier and tended to be taller (P = 0.1) than infants fed formula. Relative to NCHS values, infants had lower mean birth weights than a sample of American and European BF infants. At 6 mo, the weight of BF infants caught up to the weight of NCHS standards, while infants fed formula fell to around -1 NCHS-Z-score for weight and length. The cumulative 6-mo weight increments were negatively related to the number of episodes of diarrhea, and positively to duration of lactation (P = 0.03, R(2) = 0.17). The 6-mo length gain was negatively related to infections but not to duration of lactation (P = 0.004, R(2) = 0.19). Never-ill infants attained a better weight (P = 0.04) and length (P = 0.02) than infants who suffered one or more episodes of diarrhea. Weight and length gain of infants suffering at least one episode of diarrhea was positively related to breast-feeding and socioeconomic status. Weight increments of 15-d were positively related to breast-feeding and negatively to the introduction of solids. In conclusion, breast-feeding positively affected the growth performance of the recipient infants by averting infections and possibly by improving nutrient intake during infections.