Postnatal development of disaccharidase activities in jejunal fluid of preterm neonates.

Because human fetuses of 26-30 weeks gestation are known to have low levels of intestinal mucosal lactase activity, it has been assumed that live born preterm neonates of comparable gestational age are also lactase deficient. We have previously shown that disaccharidase activities in jejunal fluid in infants are highly significantly correlated with enzyme activities in the adjacent mucosa. We have now measured disaccharidase activities cross-sectionally and longitudinally in the jejunal fluid of a group of very preterm neonates of 26-29 weeks gestation who were fed with pasteurised human milk. Lactase activity was within the normal range for older infants and children within the first week of life. Sucrase: lactase ratios fell significantly in the second and third weeks of life, strongly suggesting a further increase in lactase activity. This increase was independent of postconceptional age. Preterm neonates are not as lactase deficient as previously believed, and this has implications in the search for optimal feeding regimes.