Growth and nutrient intake in three- to twelve-month-old infants fed human milk or formulas with varying protein concentrations. 
Results on growth and nutrient intake in infants in the second half of infancy fed human milk or formulas with varying protein concentrations in combination with supplementary foods have not previously been reported.  Seventy-one healthy infants were studied from 3 to 12 months of age.  They were exclusively breast-fed until 3 months and were then randomly assigned to one of three feeding groups, F13, F15, or F18, indicating formulas with 13, 15 or 18 g/l of protein, respectively.  Formula was gradually introduced when breast-feeding was terminated.  Infants fed breast milk only were included in the breast-fed group, and those with breast milk and formula were included in the mixed-fed group.  The same supplementary foods were provided to all infants.  There were no differences in growth between the feeding groups.  Total protein intake exceeded minimum recommendations in all groups at all ages and was higher at 6 months in F18 than in F13 (2.3 vs. 1.9 g/kg per day; p < 0.01), whereas formula protein intake was higher at all ages in F18 compared with F13.  Intake of protein from supplementary foods increased, but that from formula decreased between 6 and 12 months in all groups.  Intake of breast milk or infant formula with 13 g/l of protein along with high-protein supplementary foods provided enough protein with no adverse effect on growth.  Infants fed formulas with higher protein concentrations had similar growth, despite higher intakes of formula protein.