In Vivo Study of Colonic Fermentation of Carbohydrate in Infants

Abstract

SummaryDietary carbohydrate in the colon is fermented and converted into short‐chain fatty acids. We studied the fate of carbohydrate that arrives in the colon under circumstances similar to those that occur during an episode of diarrhea and determined whether a quantitative correlation exists among certain indicators of colonic fermentation of carbohydrate arriving in the large bowel. A stable‐isotope method was used to estimate carbon scavenging by the colon. Fourteen infants with severe malnutrition and history of watery stools and/or increased numbers of stools in the preceding 20 days were studied. Infants underwent nasocecal intubation and a 60‐min infusion of 0.5 g/kg glucose containing 5 mg/kg of 13C‐glucose. Stools were assessed for carbohydrate‐fermenting bacteria, acetate, glucose, and 13C abundance; blood was assessed for acetate; and breath was assessed for hydrogen. Some of the infants eliminated the infusate per anus within 30 min of the infusion (group I; n = 5), while others did so 120 min or more after the infusion (Group II; n = 9). The volume of fecal output after the intracecal infusion differed significantly between group I and group II (57 ± 13 vs. 24 ± 4 ml; p < 0.05). Although baseline breath hydrogen (3 ± 1 vs. 10 ± 4 parts per million) and plasma acetate (41 ± 4 vs. 47 ± 9 μM) values were not significantly different between groups, breath hydrogen values at 45 min after start of infusion were significantly lower in group I than in group II (3 ± 1 vs. 19 ± 5 ppm; p = 0.008); 60 min after start of infusion, plasma acetate levels were significantly lower in group I than in group II (34 ± 8 vs. 69 ± 11μM; p = 0.02), and the difference remained significant throughout the study. Regression analyses indicated a significant association between time elapsed from start of intracolonic infusion and plasma acetate (p = 0.014) and breath hydrogen (p = 0.04) levels for group II. Although we found good correlation between two indicators of colonic fermentation, blood acetate and breath hydrogen, these values did not correlate well with carbon scavenging or fecal bacterial counts. It is possible that the way the colon handles the infusate—i.e., water absorption and/or secretion—may affect carbohydrate fermentation.