Introduction: Human milk oligosaccharides inhibit several pathogens of pediatric populations. Their potential for protecting breast-fed infants from enteric diseases requires survival during intestinal transit.

Purpose: To determine the survival and absorption of milk oligosaccharides by comparing oligosaccharide patterns in the urine and feces of breast-fed infants with those of the milk being consumed.

Methods: Fecal and urinary oligosaccharide patterns of 17 breast-fed infants were compared with the patterns of their mothers' milk, and with the fecal and urinary patterns of paired formula-fed infants. Oligosaccharides were isolated; reduced, and the neutral species perbenzoylated, resolved by reversed-phase HPLC, and identified by coelution with authentic standards and by mass spectroscopy.

Results: Fecal oligosaccharide levels of breast-fed infants were 50-fold higher (30 nmol/mL) than fecal levels of those fed artificially(P<.05); urinary levels were quite low in breast-fed (29 pmol/mL) and even lower (3 pmol/mL) in artificially-fed infants (P<.05). Milk from individual mothers had distinctive oligosaccharide patterns that persisted in the urine and feces of their breast-fed infants.

Conclusions: The oligosaccharide peaks from formula-fed infants probably resulted from intestinal remodeling or originated from intestinal bacteria. In breast-fed infants, almost all human milk oligosaccharides survive transit through the gut, with little being absorbed followed by excretion in the urine, implying that inhibition of pathogens by human milk oligosaccharides may be functionally relevant in infants.