Digestion of human milk oligosaccharides by healty infants evaluated by the lactulose hydrogen breath test

Objective: We hypothesized that human milk oligosaccharides (HMO) would not be digested and absorbed in the infant small intestine. The purpose of the study was to quantify the extent of digestion by using the lactulose breath hydrogen test. Study design: Twenty-four healthy, breast-fed infants were studied in the home setting. Eight infants (mean age 5.2 months) who had a positive breath hydrogen response (rise > 20 ppm) to the unabsorbable sugar lactulose were given an equivalent load of HMO (0.7 to 1.0 gm/kg body weight) the following week. The breath hydrogen response to the HMO load was compared with that after lactulose by using a paired I test. Results: In seven of the eight infants, a large proportion of the HMO load reached the large intestine and was fermented. In these infants, the mean +/- SEM area under the breath hydrogen curve after HMO (5135 +/- 1148 ppm.4h) was not significantly different from that after lactulose (4949 +/- 1278 ppm.4h, p = 0.75). Conclusions: This study suggests that HMO resist digestion in the small intestine of most breast-fed infants and undergo fermentation in the colon. HMO may therefore be the source of breath hydrogen in breast-fed infants.