Exclusively breast-fed healthy infants grow slower than reference infants

We have studied the nutritional adequacy of exclusive breast-feeding by following prospectively the growth and protein nutrition of healthy infants during the 1st yr of life. The number of exclusively breast-fed infants was 116 at the age of 6 months and 36 at 9 months. These infants had slower length velocity after age 3 months than a comparison group of 32 infants who were weaned early and given formula plus solids. As a group, the exclusively breast-fed infants lagged slightly, but progressively, behind in relative length. By 9 months, 45% of them versus 18% of the comparison group showed a greater than 1 SD decrease in relative length. No such decrease was found in relative weight. Skinfolds and weight for length index showed that they were heavier for their length than the comparison infants. At 6 and 9 months the calculated protein intake (0.9 g/kg/day) was much less than the recommended amount (2.0 g/kg/day). Serum prealbumin concentration was lower than in the comparison group but this was noted as early as 4 months. No relation was found between the parameters of growth and protein nutrition either individually or in general. Whether the slower growth of the exclusively breast-fed infants represents appropriate physiological growth or whether it indicates nutritional deficiency is not known but we did not find any evidence of protein deficiency. Six infants did, however, show subsequent catch-up growth which could indicate previous malnutrition.