The nature of small bowel luminal fluid lactase

Detailed Analysis of Prebiotic Fructo- and Galacto-Oligosaccharides in the Human Small Intestine

Galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS) are food ingredients that improve human health, but their degradation throughout the human small intestine is not well understood. We studied the breakdown kinetics of FOS and GOS in the intestines of seven healthy Dutch adults. Subjects were equipped with a catheter in the distal ileum or proximal colon and consumed 5 g of chicory-derived FOS (degree of polymerization (DP) DP2-10), and 5 g of GOS (DP2-6). Postprandially, intestinal content was frequently collected until 350 min and analyzed for mono-, di-, and oligosaccharides. FOS and GOS had recoveries of 96 ± 25% and 76 ± 28%, respectively. FOS DP ≥ 2 and GOS DP ≥ 3 abundances in the distal small intestine or proximal colon matched the consumed doses, while GOS dimers (DP2) had lower recoveries, namely 22.8 ± 11.1% for β-D-gal-(1↔1)-α-D-glc+β-D-gal-(1↔1)-β-D-glc, 19.3 ± 19.1% for β-D-gal-(1 → 2)-D-glc+β-D-gal-(1 → 3)-D-glc, 43.7 ± 24.6% for β-D-gal-(1 → 6)-D-gal, and 68.0 ± 38.5% for β-D-gal-(1 → 4)-D-gal. Lactose was still present in the distal small intestine of all of the participants. To conclude, FOS DP ≥ 2 and GOS DP ≥ 3 were not degraded in the small intestine of healthy adults, while most prebiotic GOS DP2 was hydrolyzed in a structure-dependent manner. We provide evidence on the resistances of GOS with specific β-linkages in the human intestine, supporting the development of GOS prebiotics that resist small intestine digestion.

Influence of changes in lactase activity and small-intestinal mucosal growth on lactose digestion and absorption in preterm infants

BACKGROUND

Feeding intolerance (ie, achieving and maintaining full enteral feedings) is a significant problem in preterm infants. A relation exists between feeding intolerance and incomplete lactose digestion.

OBJECTIVES

We sought to identify the factors relating to lactose digestion and absorption, lactase activity, and small-intestinal mucosal growth.

DESIGN

Lactose digestion and absorption, lactase-specific activity, and lumen-to-mucosa water flux as a measure of small-intestinal mucosal surface area were determined by using the triple-lumen perfusion technique on 2 occasions 3 wk apart in 10 preterm infants (x+/-SEM gestational age: 28.0+/-0.2 wk).

RESULTS

Lactose digestion and absorption and lactase activity doubled between studies (P=0.035 and P=0.041, respectively). The change in digestion and absorption was related to lactase activity (P=0.034, R2=0.38). Lactase activity correlated with gestational age at birth (P=0.012, R2=0.51). The number of days of feeding explained 80% of the variability in small-intestinal mucosal surface area (P=0.001).

CONCLUSIONS

To our knowledge, this is the first study to measure directly lactose digestion and absorption, lactase activity, and small-intestinal surface area in preterm infants. Changes in lactose absorption relate primarily to lactase activity rather than to mucosal growth. We showed directly a relation between enteral feeding and small-intestinal mucosal growth.