An infant formula free of glycomacropeptide prevents hyperthroeninemia in formula-fed preterm infants

Background: Hyperthreoninemia is a well-known phenomenon in infants fed a w hey protein-predominant formula. Sweet whey is commonly used for the produc tion of these whey-predominant infant milk formulas. Sweet whey contains no t only whey proteins but also the threonine-rich glycomacropeptide (CMP). I n the current study, an experimental formula based on acid whey without CMP and a formula based on sweet whey with GMP (threonine content 17.2 % highe r than in the experimental formula) but otherwise with identical compositio n were tested with particular respect to threonine metabolism. Methods: Fourteen preterm infants appropriate for gestational age were enro lled in this randomized cross-over study. After a feeding period of at leas t 7 days, the nutrition of each infant was switched to the other formula fu r the second feeding period. At the end of each feeding period, the concent rations of creatinine and amino acids in the plasma and in the urine were m easured. Results: In the plasma, the threonine concentration was significantly lower in the group fed the experimental GMP-free formula than in the group fed t he sweet whey formula (P < 0.001). Renal excretion of all essential amino a cids was generally very tow and less than 2% of the intake, indicating that the kidneys had no marked homeostatic function with respect to plasma amin o acid. The plasma concentrations of the threonine metabolites glycine and serine, and that of urea were not influenced by diet. Conclusion: Feeding a whey protein-predominant bovine milk produced from ac id whey protein reduces significantly the hyperthreoninemia commonly found in formula-fed preterm infants. Thus, acid whey formulas should be recommen ded for feeding preterm infants.