Efficient assimilation of lactose carbon in premature infants

Previous studies have shown that there is minimal fecal excretion of carbohydrate energy in premature infants with high breath H2 concentrations, implying that the colon plays an important role in salvaging lactose energy. The present study extends this work by using a stable isotope method for serial assessment of lactose carbon excretion. Thus, in nine premature infants (30-32 weeks of gestation and 11-36 days of age), we conducted 23 longitudinal studies of breath hydrogen concentration and the cumulative fecal excretion of 13C derived from a single dose of [D-1-13C]lactose. The ranges of values (mean +/- SD) for breath hydrogen concentration and lactose absorption were respectively 4-440 ppm/5% CO2 (92 +/- 100) and 82-100% tracer dose (98.4 +/- 3.9). In 21 studies, lactose carbon excretion was less than 2% of the dose. There was a significant correlation between postnatal age and breath hydrogen concentration (R = 0.48; p = 0.02). These studies suggest that colonic fermentation activity is adequate for efficient colonic salvage of lactose even during the second week of life.