Neutral oligosaccharides in feces of breastfed and formula-fed infants at different ages.

Beneficial effects have been proposed for human milk oligosaccharides (HMO), as deduced from in vitro and animal studies. To date, in vivo evidence of the link between certain oligosaccharide structures in milk and their consumption by infant gut microbiota is still missing, although likely. Whereas many studies have described HMO patterns in human milk from larger cohorts, data on the excretion of HMO and possible metabolites produced in the infant gut are still very limited. From smaller-scale studies, an age-dependency according to infant gut maturation and microbiota adaptation has previously been hypothesized. To further investigate this, we profiled neutral fecal oligosaccharides from term-born infants who were exclusively breastfed, formula-fed or mixed-fed at the age of 2 months, and from a follow-up of a subgroup at 7 months of age (INFABIO study). Data on maternal antibiotic exposure was also included. Automated matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry analyses revealed the presence of HMO and metabolites in the feces of most, but not all breastfed infants at 2 months, with highly varying patterns that appeared not to differ with maternal antibiotics exposure. Formula-fed infants at 2 months and most of the breastfed infants at 7 months did not excrete HMO-like structures in their feces, the latter corresponding to the hypothesis of age-dependency. Together with our previous results that were partly contradictory to what has been proposed by others, here, we suggest alternative explanations for the described association of oligosaccharide excretion with age and feeding type in infants below 7 months of age.