Re: "Distinguishing the effects of maternal and offspring genes through studies of 'case-parent triads'" and "a new method for estimating the risk ratio in studies using case-parental control design".

In his letter, Gordon (1) raises questions concerning the findings of our prospective cohort study of breastfeeding and respiratory illness (2) based on his unproven speculations about the etiology of respiratory illnesses in children. In a series of previous letters to the editor, he has advanced a "mechanical theory" for the occurrence of respiratory and gastrointestinal illnesses in infants. His proposed "sompe syndrome"—that "pooling of liquids in the middle ear, with secondary reflux down the eustachian tubes into the stomach and lungs, [causes] gastroenteritis and pneumonia" (1, p. 427)—seems implausible. While his theory may not have been "refuted," it is hardly established and is not well supported by a broad understanding of pathogenic mechanisms of respiratory infection in infants. Our paper (2) offers strong evidence for a role of breastfeeding in lowering the risk of respiratory illnesses in infants during the first 6 months of life, and the findings have no relevance to Gordon's speculations.