Age at First Introduction of Cow Milk Products and Other Food Products in Relation to Infant Atopic Manifestations in the First 2 Years of Life: The KOALA Birth Cohort Study

Abstract

To evaluate any associations between the introduction of cow's milk products/other solid food products and infant atopic manifestations in the second year of life.Mother-infant pairs previously enrolled in the ongoing prospective KOALA Birth Cohort Study to study the cause of allergic disease. A total of 2834 pregnant women were recruited at 34 weeks of gestation. Data from 2558 infants in the Netherlands were analyzed.Data on introduction of cow's milk products and other food products, eczema, recurrent wheeze, allergies, and confounders were collected with repeated questionnaires at 34 weeks of gestation and 3, 7, 12, and 24 months after delivery. Allergen-specific immunoglobulin E was assessed from serum obtained from children at age 2 years. Analyses were performed through multivariate logistic regression. Reverse causation was addressed by performing risk-period-specific analyses that excluded infants with early symptoms of eczema or wheeze.More delay (eg, >7 months of age) in introduction of cow's milk products was associated with a higher risk for eczema. In addition, delayed introduction of other food products was associated with an increased risk for atopy development at the age of 2 years. Exclusion of infants with early symptoms of eczema and recurrent wheeze (to avoid reverse causation) did not essentially change the results.Delaying the introduction of cow's milk products or other food products may not be favorable for preventing the development of atopy.In giving advice to “allergic families,” we used to think that it was a good idea to keep children clean, away from pets, and to delay the introduction of “highly allergenic” foods such as cow's milk. Were we wrong on all counts? There are many confounders when evaluating the relationship between early introduction of food products to infants and later development of atopy. The authors of this article used several statistical approaches to account for the main confounders, including breastfeeding, family history, and, importantly, reverse causation. Although it is difficult to absolutely exclude reverse causation, this authors suggested that delayed introduction of milk was associated with increased eczema. Because of studies such as this one, the focus has shifted away from the delayed introduction of cow's milk protein and other food products as a means to decrease the risk of developing atopy. These findings provide a rationale for conducting interventional studies to determine whether early introduction of milk and other foods will actually help to prevent food allergies.