Comparison of inulin and lactulose as reference standards in the breath hydrogen test assessment of carbohydrate malabsorption in patients with chronic pancreatic exocrine insufficiency

Colonic energy salvage in chronic pancreatic exocrine insufficiency

BACKGROUND

Chronic pancreatic exocrine insufficiency results in maldigestion. As a result, increased amounts of undigested nutrients reach the colon, providing more substrate for bacterial fermentation to produce short-chain fatty acids, which could therefore provide additional energy supplement.

METHODS

This study aimed to assess carbohydrate malabsorption in patients with chronic pancreatic exocrine insufficiency after ingestion of a standard diet and to calculate energy salvaged by colonic bacterial metabolism. A 72-hour stool collection was done on 10 adult patients receiving a 3-day standard diet containing 100 g fat, 329 g carbohydrate, and 154 g protein, and short-chain fatty acids, fat, carbohydrate, and nitrogen excretion were assessed. A breath hydrogen test after ingestion of 200 g (dry weight) cooked maize meal (test meal) and 10 g oral inulin (standard), respectively, was subsequently done on the patients and 15 healthy adult controls.

RESULTS

Breath hydrogen production after ingestion of maize meal and inulin, respectively, and calculated carbohydrate malabsorption were significantly greater in patients (21.4% +/- 17%) than in controls (10.2 +/- 1.4%; p < .05). Patients malabsorbed 70.4 g/d (281.6 kcal) carbohydrate in the standard diet. Total carbohydrate loss in stool amounted to 8.1 g/d (2.4%), and 62.3 g/d (19%) was hence salvaged as short-chain fatty acids for energy provision. Colonic bacterial fermentation therefore converted 88.5% of malabsorbed carbohydrate to short-chain fatty acids, 92.8% of which was absorbed and 7.2% excreted. This suggests that 10.2% of energy expenditure/requirement in these patients is derived from salvage of malabsorbed carbohydrate.

CONCLUSIONS

Colonic bacterial metabolism is a significant source of energy salvage in patients with pancreatic enzyme deficiency.

Influence of dietary fiber on inflammatory bowel disease and colon cancer: importance of fermentation pattern

The benefits of dietary fiber on inflammatory bowel disease may be related to the fermentative production of butyrate in the colon, which appears to decrease the inflammatory response. The benefits of dietary fiber against colon cancer may be related to both fermentative and non-fermentative processes, although poorly fermentable fibers appear more influential. Dietary fiber fermentation profiles are important in determining optimal fibers for colonic health, and may be a function of structure, processing conditions, and other food components. A greater understanding of the relationships between fermentation rate and dietary fiber structure would allow for development of dietary fibers for optimum colonic health.

Colonic fermentation of indigestible carbohydrates contributes to the second-meal effect

BACKGROUND

Low postprandial blood glucose is associated with low risk of metabolic diseases. A meal's ability to diminish the glucose response to carbohydrates eaten during the following meal is known as the "second-meal effect" (SME). The reduced glycemia elicited by low-glycemic-index (LGI) foods consumed during the first meal has been suggested as the main mechanism for SME. However, LGI foods often increase colonic fermentation because of the presence of fiber and resistant starch.

OBJECTIVE

The objective was to study the SME of greater fermentation of high-glycemic-index (HGI) and LGI carbohydrates eaten during a previous meal.

DESIGN

Ten healthy volunteers ate 3 breakfast test meals consisting of sponge cakes made with rapidly digestible, nonfermentable amylopectin starch plus cellulose (HGI meal), amylopectin starch plus the fermentable disaccharide lactulose (HGI-Lac meal), or slowly digestible, partly fermentable amylose starch plus cellulose (LGI meal). Five hours later, subjects were fed the same standard lunch containing 93 g available carbohydrates. Blood was collected for measurement of glucose, insulin, and nonesterified fatty acids (NEFAs). Breath hydrogen was measured as a marker of colonic fermentation. Postlunch gastric emptying was measured by using ultrasonography.

RESULTS

Both the HGI-Lac and LGI meals improved glucose tolerance at lunch. In the case of the HGI-Lac meal, this effect was concomitant with low NEFA concentrations and delayed gastric emptying.

CONCLUSION

Fermentable carbohydrates, independent of their effect on a food's glycemic index, have the potential to regulate postprandial responses to a second meal by reducing NEFA competition for glucose disposal and, to a minor extent, by affecting intestinal motility.