Modeling 13C breath curves to determine site and extent of starch digestion and fermentation in infants

Background: The colon salvages energy from starch. especially when the capacity of the small intestine to digest it is limited. The aim of this Study was to determine the site and relative extent of starch digestion and fermentation in infants. Methods: Thirteen infants (10 male and 3 female infants), median age 11.8 months (range, 7.6-22.7 months), were fed a starchy breakfast containing C-13-labeled wheat flour after an overnight fast. Duplicate breath samples were obtained before breakfast and every 30 minutes for 12 hours. Breath (CO2)-C-13 enrichment was measured using isotope ratio mass spectrometry, and results were expressed as percentage dose recovered PDR) for each 30 minutes. The PDR data were analyzed and mathematically modeled assuming either a constant estimate of CO, production rate or adjusted for physical activity. Results: Mean +/- SD cumulative C-13 PDR (cPDR) at 12 hours was 21.3% +/- 8.4% for unadjusted data and 26.5% +/- 11.6% for adjusted data. A composite model of two curves fit significantly better than a single curve. Modeling allowed estimation of cPDRs of small intestine (17.5% +/- 6.5% and 22.7% +/- 9.3% for unadjusted and adjusted data, respectively) and colon (4.6% +/- 2.9% and 6.3% +/- 5.4%). Conclusions: Modeling of (CO2)-C-13 enrichment curves after ingestion of C-13-enriched wheat flour is an attractive means to estimate the contribution of the upper and lower gut to starch digestion and fermentation.