A Combined 13CO2/H2 Breath Test Can Be Used to Assess Starch Digestion and Fermentation in Humans

Ingestion of starch from corn (naturally enriched with 13C) should produce 13CO2 after small intestinal digestion and 13CO2 and H2 from colonic fermentation. This study used a combined 13CO2/H2 breath test to assess the digestion and fermentation of resistant starch and to show that the test could detect changes in digestibility due to cooking. Volunteers consumed 40 g digestible cornstarch with water (n = 8), or 40 g resistant cornstarch in liquid (n = 12) or cooked into a pancake (n = 4). Interval breath sampling was performed and analyzed for 13CO2 and H2. Ingestion of resistant starch produced a double-peaked 13CO2 excretion curve. The first increase in 13CO2 occurred at the same time as excretion from digestible starch (55 ± 9 and 68 ± 9 min, respectively), which was due to small intestinal digestion. The second increase in 13CO2 was accompanied by an increase in H2 excretion (432 ± 15 and 428 ± 48 min, respectively), which was indicative of colonic bacterial fermentation. Cooking resistant starch increased its degree of digestion from 36 to 72%. The 13CO2/H2 breath test can be used to estimate digestion and fermentation of starches in different physiologic and pathologic conditions.