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.


METHODS
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.


CONCLUSIONS
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.
Brighenti
Furio
F
Human Nutrition Unit, Department of Public Health, University of Parma, Via Volturno 39, 43100 Parma, Italy. furio.brighenti@unipr.it
Benini
Luigi
L
Del Rio
Daniele
D
Casiraghi
Cristina
C
Pellegrini
Nicoletta
N
Scazzina
Francesca
F
Jenkins
David J A
DJ
Vantini
Italo
I
D000328:Adult; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism*; D001944:Breath Tests; D003106:Colon / Q000378:metabolism*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism*; D004043:Dietary Fiber / Q000008:administration & dosage / Q000378:metabolism*; D004063:Digestion; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005260:Female; D005285:Fermentation; D005746:Gastric Emptying / Q000187:drug effects; D005769:Gastrointestinal Motility / Q000187:drug effects* / Q000502:physiology; D038321:Glycemic Index; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D007328:Insulin / Q000097:blood; D008297:Male; D019518:Postprandial Period; D013270:Stomach / Q000000981:diagnostic imaging; D014463:Ultrasonography
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D006859:Hydrogen