Increased kidney growth in formula-fed versus breast-fed healthy infants
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A high protein intake results in increased kidney growth and glomerular filtration rate in human adults and young rats. It is unknown whether kidney size in young infants is influenced by increased protein intake in formula-fed compared with breast-fed infants. We investigated the effect of formula versus breast feeding on kidney growth in a cohort of 631 healthy children examined at birth, and at 3 and 18 months of age. Kidney size was determined by ultrasonography and related to gender, age, body size, and feeding category (fully breast fed, partially breast fed, or fully formula fed at 3 months). Serum urea nitrogen, serum creatinine, and estimated creatinine clearance were measured at 3 months of age. Kidney growth and serum urea nitrogen were significantly increased in partially or fully formula-fed 3-month-old infants. This effect was more pronounced in boys than in girls. The changes in relative kidney size were temporary, as they did not persist at 18 months of age, when all children received a normal mixed diet. The immediate renal effects of formula feeding should be taken into consideration for recommendations concerning infant feeding. Whether there are any long-term effects of early increased protein intake on later kidney function remains to be seen.
KeywordsProtein Breast milk Formula Kidney growth Infant Gender
We are grateful to the participating families and to the staff of the Obstetric Departments of the University Hospital of Copenhagen for excellent cooperation. We appreciate the skilled help of our assisting nurses and students, and we thank Kim Fleischer Michaelsen and the staff at the Human Milk Bank at Hvidovre Hospital, for generously letting us use their laboratory facilities. The present study was supported by: the Danish Research Council (no. 9700833), Research Foundation of The Copenhagen Hospital Corporation (no. 109/00 and 134), the European Commission (no. QLK4–1999–01422 and QLRT-2001–00269), and the Ville Heise Foundation.
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