IN-VIVO LACTOSE DIGESTION IN PRETERM INFANTS

In vitro studies of intestinal lactase activity and breath-hydrogen st udies have suggested that the capacity for lactose digestion in preter m infants is less than the usual intake. To explore this question usin g an in vivo approach, we determined the fraction of dietary lactose h ydrolyzed to glucose (and galactose) in 14 preterm infants with a gest ational age of 26-31 wk at the time of birth but a postconceptional ag e of 31-37 wk at the time of study. The percentage of lactose digested was estimated after 6-h, primed, constant gastric infusions of [1-C-1 3]glucose and D-[-1-C-13]lactose on alternate days. A coefficient of l actose fermentation was derived from the rates of pulmonary excretion of hydrogen and carbon dioxide. Mean (+/- SD) lactose digestion was 79 +/- 26%. There was a significant inverse rank (r = -0.799, p < 0.01) and linear (r = -0.587, P < 0.05) correlation between this variable an d postconceptional age. The percentage of lactose fermented averaged 3 5 +/- 27%.