The association between prolonged breastfeeding and poor growth--what are the implications?

The smaller size of breast fed children in infancy and thereafter in malnourished and well-nourished populations has resulted in rushes to judgement that have been shown to be ill-advised. The reasons for the smaller size in malnourished populations is due to retaining the small and sickly child at the breast (reverse causality) and the consequent continuing sickliness of this breast fed child (negative confounding). Once the reverse causality and negative confounding have been taken into account breast feeding improves growth, at least through the second year of life. Thus prolonged breastfeeding should always be fostered, especially in malnourished populations. An exception remains when breast milk may transmit disease to the suckling child. In well-nourished populations the magnitude of the difference between breast fed and weaned children is much less than in malnourished populations, is observed to increase over the first year of life, but to have disappeared by the end of the second year. One may never-the-less be concerned that complimentary feeding practices are not adequate for these children.