Lactose malabsorption by premature infants: magnitude and clinical significance.

Sequential studies of breath hydrogen excretion in response to lactose feeding were carried out in 22 premature infants during the first seven weeks of life. Seventy-five percent of infants excreted H2 in breath during the first two weeks, 100% by the end of the third week. The peak H2 concentration and the five-hour mean breath H2 excretions were significantly related to lactose intake per day, lactose intake per feeding and postnatal age, though only lactose intake per day remained significant when all three variables were included in multiple regression analysis. Preprandial breath H2 concentration was inversely related to the frequency of feeding. Using the five-hour mean H2 excretion, it was estimated that 66% or more of ingested lactose entered the colon and was fermented. Throughout the studies stool patterns and rates of weight gain of the infants were normal. Premature infants normally malabsorb substantial amounts of lactose. The elevation of breath H2 in these infants apparently represents a successful adaptation of the colonic microflora to this physiologic malabsorption and should not be cause to modify the diet of an infant who is clinically well.