Human milk and preterm formula compared for effects on growth and metabolism.

Metabolic tolerance to a 'premature formula' feed was studied in a group of small immature infants, mean (SD) gestation 27.8 (1.4) weeks. Ten infants weighing 880-1295 g at the time of the study were fed on SMA low birthweight formula for a mean (SD) of 23.5 (5.5) days and were compared with 10 who were fed on expressed breast milk for 25.8 (6.1) days. The infants were well matched for weight, gestation, and postnatal age at the time of the study and were receiving full enteral feeds. They were investigated by balance techniques and plasma sampling on at least two occasions. Ten larger infants weighing 1330-1740 g and being fed on the same formula feed were also studied as an additional control group. Formula fed infants retained more nitrogen and gained weight faster. Plasma phosphorus concentrations were higher in the group fed on the formula feed, and alkaline phosphatase activity was lower. There were no significant differences in plasma concentrations of urea, electrolytes, or albumin or in acid base status. Taurine and arginine concentrations were higher in the group being breast fed, but there were no other significant differences in plasma amino acids, and no toxic concentrations occurred after either feed. The results of this study show that this formula (and presumably other feeds of similar composition) seem to be metabolically safe for the smallest infants.