Total glutamine content in human milk is not influenced by gestational age

Background: Glutamine may be a conditionally indispensable amino acid in neonates and should be given in adequate amounts. Reliable information concerning the glutamine content of human milk is lacking. Aim: To assess total glutamine content in human milk using a novel analytical procedure, and to evaluate the potential influence of time of delivery and lactational stage. Methods: The content of free and protein‐bound glutamine was assessed in transitional (days 4–7 of lactation) and mature (days 29–34) human milk, after preterm (37 wk, n=20) delivery. Milk samples were obtained by manual expression and stored at ≤70°C. Measurement of protein‐bound glutamine was performed after stabilization by bis(1,1‐trifluoroacetoxy)iodobenzene (BTI). Free glutamine was detected by HPLC. Results: There was no difference concerning glutamine content in human milk after term or preterm delivery (median of 5000 vs 4960 µmol/l milk). The protein‐bound glutamine content decreased with the duration of lactation (6230 vs 4540 µmol/l milk). Free glutamine accounted for only 3–10% of the protein‐bound glutamine content. The free glutamine content showed a high variability after preterm and term delivery. Conclusion: This study presents for the first time data on glutamine intake in preterm and term neonates fed human milk. With these data, it is possible to formulate adequately composed nutritional therapy for infants at risk of glutamine imbalance.