13C and H2 Breath Tests to Study Extent and Site of Starch Digestion in Children with Cystic Fibrosis

Abstract

Starch is an important source of energy for children with cystic fibrosis, but little is known about their capacity to digest it.

A 13C breath test was used to measure starch digestion and oxidation in 16 children with cystic fibrosis (median [range] age, 7.9 [4-15] years; 7 girls, 9 boys) and 5 normal healthy control subjects (median age, 8.3 [7-13] years; 3 girls, 2 boys). A test meal of 13C flour and lactulose was consumed and breath samples were obtained half-hourly thereafter for 6 hours to measure 13C enrichment by isotope ratio mass spectrometry and H2 by electrochemistry. The test was repeated on 10 children with cystic fibrosis when they were taking pancreatic supplements.

The median (range) cumulative percentage 13C dose recovery (cPDR), was 35% (18-52%) in control subjects, 18% (9-33%) in children with cystic fibrosis without enzymes, and 29% (22-51%) in those with pancreatic supplements. cPDR differed significantly between healthy control subjects and children with cystic fibrosis without enzymes (p = 0.01) and between children with cystic fibrosis with and without enzymes (p < 0.0001), but there was no difference between control subjects and children with cystic fibrosis taking enzymes (p = 0.5). Eight children with cystic fibrosis had a cPDR within control range, and in six there was a second peak in 13CO2 enrichment coincident with an increase in H2.

Starch digestion and oxidation are diminished in children with cystic fibrosis, but pancreatic enzymes restored them to near normal levels. A second peak in 13CO2 enrichment, suggestive of colonic starch fermentation was absent in healthy children, but present in some children with cystic fibrosis and abolished by pancreatic enzymes.