Breastfeeding, asthma, and atopic disease: an epidemiological review of the literature.

Two main types of observational epidemiological studies have been used to question whether breastfeeding protects children from developing atopic disease and asthma. These are cohort studies of random samples of children and cohort studies of children with a family history of asthma or atopy. In each study type, exposure and outcome data are collected either prospectively or retrospectively. In this review, the primary objective was to assess the evidence of whether breastfeeding protects against asthma and atopic disease. As an outcome of this review, an analytical perspective with clinical implications is given.