Sir.—One of the major limitations of the study by Duncan et al1 regarding the growth velocity in exclusively breast-fed infants is, as the authors point out, the lack of a suitable control group of infants; however, the major finding in the study of significantly reduced rates of growth in both weight and length in exclusively breast-fed infants compared with National Center for Health Statistics standards deserves comment.
As the authors note in their discussion, many others have described the decreased rate of weight gain in breast-fed infants, but there is little information regarding rate of gain in length. We suggest a reason for the decreased rate of growth in length in the breast-fed infants in this study.
The 33 infants in the study apparently were truly exclusively breast-fed for the first six months of life without any supplemental vitamins or minerals. In most of the other references cited