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Background Information about the extent of carbohydrate digestion and fermentation is critical to our ability to explore the metabolic effects of carbohydrate fermentation in vivo. We used cooked (13)C-labelled barley kernels, which are rich in indigestible carbohydrates, to develop a method which makes it possible to distinguish between and to assess carbohydrate digestion and fermentation. Materials and methods Seventeen volunteers ingested 86 g (dry weight) of cooked naturally (13)C enriched barley kernels after an overnight fast. (13)CO(2) and H(2) in breath samples were measured every half hour for 12 h. The data of (13)CO(2) in breath before the start of the fermentation were used to fit the curve representing the digestion phase. The difference between the area under curve (AUC) of the fitted digestion curve and the AUC of the observed curve was regarded to represent the fermentation part. Different approaches were applied to determine the proportion of the (13)C-dose available for digestion and fermentation. Results Four hours after intake of barley, H(2)-excretion in breath started to rise. Within 12 h, 24-48% of the (13)C-dose was recovered as (13)CO(2), of which 18-19% was derived from colonic fermentation and the rest from digestion. By extrapolating the curve to baseline, it was estimated that eventually 24-25% of the total available (13)C in barley would be derived from colon fermentation. Conclusion Curve fitting, using (13)CO(2)- and H(2)-breath data, is a feasible and non-invasive method to assess carbohydrate digestion and fermentation after consumption of (13)C enriched starchy food.

Background Information about the extent of carbohydrate digestion and fermentation is critical to our ability to explore the metabolic effects of carbohydrate fermentation in vivo. We used cooked (13)C-labelled barley kernels, which are rich in indigestible carbohydrates, to develop a method which makes it possible to distinguish between and to assess carbohydrate digestion and fermentation.Materials and methods Seventeen volunteers ingested 86 g (dry weight) of cooked naturally (13)C enriched barley kernels after an overnight fast. (13)CO(2) and H(2) in breath samples were measured every half hour for 12 h. The data of (13)CO(2) in breath before the start of the fermentation were used to fit the curve representing the digestion phase. The difference between the area under curve (AUC) of the fitted digestion curve and the AUC of the observed curve was regarded to represent the fermentation part. Different approaches were applied to determine the proportion of the (13)C-dose available for digestion and fermentation.Results Four hours after intake of barley, H(2)-excretion in breath started to rise. Within 12 h, 24-48% of the (13)C-dose was recovered as (13)CO(2), of which 18-19% was derived from colonic fermentation and the rest from digestion. By extrapolating the curve to baseline, it was estimated that eventually 24-25% of the total available (13)C in barley would be derived from colon fermentation.Conclusion Curve fitting, using (13)CO(2)- and H(2)-breath data, is a feasible and non-invasive method to assess carbohydrate digestion and fermentation after consumption of (13)C enriched starchy food.

Background Small intestinal and oro-cecal transit time (OCTT) is determined for clinical diagnostics and research purposes. Experimental protocols used vary with respect to the inclusion of a subsequent meal during the test period. This study was conducted to elucidate whether the ingestion of a subsequent meal during the test period influences the OCTT of the test meal. Materials and methods The OCTT of a liquid test meal, measured with the lactose-[C-13]ureide breath test, was compared between four groups of healthy volunteers (n = 36) who consumed the subsequent meal at different time points. Also, the OCTT was determined twice in eight subjects; a subsequent meal was ingested after 180 min (test A) and after 360 min (test B). Results An apparently meal-related increase in median OCTT was observed. The OCTT of the eight volunteers measured in test A (210; 210-349 median; quartiles) was significantly shorter than that found in test B (345; 300-375 min, P = 0.016). As result of the ingestion of the subsequent meal at 180 min the OCTT was shortened by 90; 64-116 min in 7/8 subjects. Conclusion These data indicate that the ingestion of a subsequent meal affects the OCTT of a liquid test meal. This phenomenon could be explained by the increased intestinal motility in response to a meal, and should be taken into account when designing protocols for measurements of the OCTT and in the interpretation of small intestinal absorption studies.

Background Small intestinal and oro-cecal transit time (OCTT) is determined for clinical diagnostics and research purposes. Experimental protocols used vary with respect to the inclusion of a subsequent meal during the test period. This study was conducted to elucidate whether the ingestion of a subsequent meal during the test period influences the OCTT of the test meal.Materials and methods The OCTT of a liquid test meal, measured with the lactose-[C-13]ureide breath test, was compared between four groups of healthy volunteers (n = 36) who consumed the subsequent meal at different time points. Also, the OCTT was determined twice in eight subjects; a subsequent meal was ingested after 180 min (test A) and after 360 min (test B).Results An apparently meal-related increase in median OCTT was observed. The OCTT of the eight volunteers measured in test A (210; 210-349 median; quartiles) was significantly shorter than that found in test B (345; 300-375 min, P = 0.016). As result of the ingestion of the subsequent meal at 180 min the OCTT was shortened by 90; 64-116 min in 7/8 subjects.Conclusion These data indicate that the ingestion of a subsequent meal affects the OCTT of a liquid test meal. This phenomenon could be explained by the increased intestinal motility in response to a meal, and should be taken into account when designing protocols for measurements of the OCTT and in the interpretation of small intestinal absorption studies.

Defects in lipolysis due to pancreatic insufficiency can be diagnosed by the mixed triglyceride (MTG) (CO2)-C-13 breath test. However, the effects of various test conditions on the (CO2)-C-13 response have only been partially elucidated. In healthy adults, we performed the (CO2)-C-13 mixed triglyceride breath test and we compared (a) the inter- and intra-individual variation in the (CO2)-C-13 response; (b) the effect of two different test meals; (c) the effect of an additional meal during the test; and (d) the effect of physical exercise during the test. Upon repeating the test in the same individual (test meal cream), repeatability coefficients were large, with respect to either time to maximum C-13 excretion rate (3.8 h), maximum C-13 excretion rate (4.9% C-13 dose h(-1)) or cumulative recovery of C-13 over the 9-h study period (22.7% C-13 dose). The cumulative C-13 expiration over 9 h obtained with the test meal composed of cream was quantitatively similar to that obtained with bread and butter: 42.2 +/- 8.4% and 47.7 +/- 6.3% respectively. Fasting for 9 h during the test resulted in similar C-13 expiration rates and cumulative C-13 expiration (43.4% +/- 7.2%) when compared with consumption of an additional meal 3 h after the start of the test (38.3 +/- 5.3%). The (CO2)-C-13 response increased in five out of seven subjects, but decreased in the other two, when moderate exercise was performed (bicycle ergometer, 50 W for 5 h). We conclude that the repeatability of the MTG test in healthy adults is low. The present results indicate that a solid and a liquid test meal, containing a similar amount of fats, give similar cumulative (CO2)-C-13 responses, and that stringent prolonged fasting during the test is unnecessary. Standardization of physical activity seems preferable, since the unequivocal effects of moderate exercise on the (CO2)-C-13 response were observed in the individuals studied.

Fasting plasma secretin determined in nine healthy subjects, twelve patients with active duodenal ulcer and four with Zollinger-Ellison syndrome were 3.2 +/- 0.4, 5.1 +/- 1.2 and 20.3 +/- 1.3 pmol/l respectively (mean +/- SEM). Cimetidine significantly (P less than 0.05) reduced levels in those with duodenal ulcer, as did gastric aspiration in the Zollinger-Ellison group. A significant correlation (P less than 0.001) was found between basal acid output and mean fasting plasma secretin. After a solid meal and subsequent liquid soft drink, no sustained mean rise in plasma secretin was observed; changes in secretin appeared to coincide in time with rapid falls in duodenal pH, though little relationship could be established between the absolute level of pH and changes in plasma secretin. The mean peak post-prandial rise in plasma secretin observed after solids was significantly (P less than 0.05) greater in duodenal ulcer patients than controls (9.1 +/- 1.1 versus 6.7 +/- 0.5 pmol/l) as was the mean integrated post-prandial release (1002 +/- 110 versus 710 +/- 67 pmol min-1 1(-1)). Cimetidine reduced both rises (P less than 0.05) and was associated with significantly less duodenal pH readings below 4 (P less than 0.001). These results suggest that gastric acid is a major release mechanism for plasma secretin both fasting and after meals but it is likely the acid load rather than absolute pH in the duodenum which determines circulating levels.