Characterization of oligosaccharides in milk and feces of breast-fed infants by high-performance anion-exchange chromatography.

Human milk contains a large amount of oligosaccharides, which represent its third largest solute. Nevertheless, both the metabolism and the role of these substances are still largely unknown. A previous study we conducted documented that the amount of oligosaccharides excreted in the feces varies from 6% to 13% of the 24-hour ingested oligosaccharides. The aim of this study was to characterize the pattern of oligosaccharides in the feces compared with the pattern of the ingested milk. Six term newborn infants were studied at the end of the first month of life. A 7:00 AM milk sample was obtained with an electric breast pump. Feces were collected during the day of milk sampling. Analyses of oligosaccharides were performed using high-pH anion-exchange chromatography with pulsed amperometer detection. Pure milk oligosaccharides were used as reference standards. The chromatographic profile of the oligosaccharides present in the feces and in the milk samples showed more than 40 peaks, 20 of which have been identified. The oligosaccharide profile observed in the feces was similar to the pattern of oligosaccharides present in the milk ingested. A significant difference was represented by the almost complete absence of lactose in the feces of all infants and of sialyllacto-N-tetraose a and disialyllacto-N-neotetraose in 3 samples. A substantial reduction of lacto-N-tetraose was observed in 5 samples. Our results demonstrate that the oligosaccharide profile in the feces is similar to that of the ingested milk. Approximately 40% to 50% of the total ingested oligosaccharides can be found in feces of breast-fed infants.