Gut transit and carbohydrate uptake

Abstract

Classical assessments of nutritional adequacy rely on tables of supposed nutrient requirements for animals or for man on the one hand, and the ability of feedstuffs to provide them on the other. These are expressed in gross or overall digestibility terms and do not relate to differences in the rates of amounts of digestion occumng in different parts of the gut. Yet in the case of carbohydrates, these differences in the pattern of digestion are factors which have a considerable bearing on animal growth, or human metabolism, e.g. in the diabetic state. The aim of the present review is to consider the importance of interrelations between transit, digestion, fermentation and absorption of carbohydrates. Examples will be drawn from studies in man and related information from the pig which appears to digest, absorb and metabolize carbohydrates in a similar way to human beings.From a nutritional and physiological point of view carbohydrates exhibit great diversity. In general, man and most animals are able to hydrolyse starch thoroughly and to absorb sugars rapidly in the small intestine. However, a substantial part of dietary carbohydrate can be in the form of non-starch polysaccharide (NSP; equivalent to dietary fibre): this is not hydrolysed by amylase, but is fermented by the gut microflora to a degree depending on its physical and chemical structure.

Effect of psyllium on gastric emptying, hunger feeling and food intake in normal volunteers: a double blind study

“…(3) Another possibility is that psyllium retains alimentary fats into the gastric lumen by modifying motor activity of the gastric muscle (Jenkins et al, 1978). Fat content Inhibition of food intake by psyllium D Rigaud et al is able to modify the effect of dietary ®bre on hunger (Low et al, 1988;Cummings et al, 1979). Unfortunately, we did not study the gastric emptying time of fats, because of the inaccuracy of the methods using labeled fat in mixed meal.…”

“…It has been shown that the increased viscosity of the food obtained with soluble ®bres may further reduce the rate of small intestinal absorption. Indeed an increase in the viscosity of food may have several effects: (a) to slow down the small intestinal transit (Low, 1988;Cherbut et al, 1994); but Cummings et al (1979) did not ®nd any modi®cation of oro-cecal transit time with pectin; (b) to reduce the interaction between food nutrients and digestive enzymes (Flourie  et al, 1984;Cummings et al, 1979; to increase the time for nutrient diffusion, by increasing the thickness of the unstirred water layer (Flourie  et al, 1984;Rydning & Berstad, 1986). This is consistent with the studies which have demonstrated that soluble ®bres could decrease the area under the curve of serum glucose after a duodenal glucose load (Berggren et al, 1993).…”

Rates of energy processing by blowflies: the uses for a joule vary with food quality and quantity

“…Cockroaches assimilate 95-98% of ingested glucose regardless of concentration (O.CM-l.Omoll" 1 ; Treherne, 1957). Humans digest and absorb essentially all ingested simple sugars (Low, 1988). Measurements of the refractive index of excreted fluid for painted lady butterflies (Vanessa cardui) indicate 96-98 % assimilation for 0.5-1.5moll" 1 sucrose (F. R. Hainsworth, in preparation).…”

Bacteroides thetaiotaomicron Starch Utilization Promotes Quercetin Degradation and Butyrate Production by Eubacterium ramulus

“…Degradation of this flavonoid results in the production of 3,4-dihydroxyphenylacetic acid (DOPAC), which has antiproliferative activity in colon cancer cells (Schneider and Blaut, 2000; Schneider et al, 2000; Gao et al, 2006). Nevertheless, glucose is rapidly absorbed in the small intestine and negligible amounts reach the colon, where E. ramulus resides (Low, 1988).…”