Investigation of free amino acid concentration in Japanese mother fs breast milk at 4–5 days after giving birth

Abstract

AimBreast milk contains numerous nutrients such as carbohydrate dominated by lactose, lipids, proteins and free amino acids (FAAs). The non‐protein nitrogen fraction that includes FAAs has been studied extensively and their important physiological roles in infant nutrition and development have been elucidated. However, the knowledge of FAAs in the milk and supports data for its physiological levels are limited. The aim of this study was to determine the concentrations of FFAs and influence of food intake on FAAs in breast milk of Japanese women.MethodsSubjects, 12 mothers, living in Kumamoto were recruited to supply breast milk samples. Approximately 15 mL of breast milk was obtained at a time by assistance of maternity nurses, collecting in propylene tube, immediate placed in ice and stored in deep freezer until analysis. The FAAs in respective samples were carried out by deproteinization with 0.3% (w/v) sulfosalicylic acid solution, filtration with 0.45 um pore size filter, ultrafiltration with 10K filter, and amino acid contents analysis by Hitachi L‐8900 amino acid analyzer.Results and ConclusionsBreast milk contained high concentrations of glutamic acid (Glu), which was over 20% of total FFAs. Furthermore, Glu concentrations increased at 1 and 2.5 hours after the meal, but other FAAs are not changed by eating a meal. The FAAs concentration in breast milk seems well maintained with the exception of Glu.