Delayed Complete Functional Lactase Sufficiency in BreastFed Infants

Colonic fermentation of unabsorbed lactose was evaluated by measuring breath hydrogen BH2after a regular feeding in 17 white, normal, exclusively breastfed infants 45 weeks of age. Interval breath samples were collected with a specially modified face mask and analyzed by gas chromatography for H2and CO2concentrations. Five infants 29 produced 20 ppm or more of H2, four of whom underwent repeated testing. Three infants stopped producing over 20 ppm of H2as they grew older. On a repeat evaluation, one of these three infants had levels over 20 ppm when other foods were introduced into his diet. The other continued to have elevated BH2when weaned. Stools of infants with elevated BH2levels had no detectable glucose, and pH was over 5.5. Weightforage of infants with elevated BH2was at or above the 75th percentile. BH2levels, normalized for the amount of breast milk ingested, fell significantly with age. These results show that complete small bowel absorption of lactose from breast milk does not occur in all white, normal, term, appropriateforgestationalage infants in the first months of life. The absence of glucose in the stool and the normal stool pH suggest that the unabsorbed lactose that produced H2can be degraded in the colon.