John H. Cummings

For nutritional purposes, starch in foods may be classified into rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). RS may be further divided into three categories according to the reason for resistance to digestion. A method is reported for the measurement of total starch, RDS, SDS, RS and three RS fractions in starchy foods, using controlled enzymic hydrolysis with pancreatin and amyloglucosidase. The released glucose is measured by colorimetry, using a glucose oxidase kit. Values for RDS and SDS in foods obtained by the method reflect the rate of starch digestion in vivo. Values for RS are similar to the amounts of starch escaping digestion in the small intestine of ileostomates, and are a guide to the amounts of starch likely to enter the colon for fermentation. Results are given for a number of starchy foods.

Evidence for the occurrence of microbial breakdown of carbohydrate in the human colon has been sought by measuring short chain fatty acid (SCFA) concentrations in the contents of all regions of the large intestine and in portal, hepatic and peripheral venous blood obtained at autopsy of sudden death victims within four hours of death. Total SCFA concentration (mmol/kg) was low in the terminal ileum at 13 +/- 6 but high in all regions of the colon ranging from 131 +/- 9 in the caecum to 80 +/- 11 in the descending colon. The presence of branched chain fatty acids was also noted. A significant trend from high to low concentrations was found on passing distally from caecum to descending colon. pH also changed with region from 5.6 +/- 0.2 in the caecum to 6.6 +/- 0.1 in the descending colon. pH and SCFA concentrations were inversely related. Total SCFA (mumol/l) in blood was, portal 375 +/- 70, hepatic 148 +/- 42 and peripheral 79 +/- 22. In all samples acetate was the principal anion but molar ratios of the three principal SCFA changed on going from colonic contents to portal blood to hepatic vein indicating greater uptake of butyrate by the colonic epithelium and propionate by the liver. These data indicate that substantial carbohydrate, and possibly protein, fermentation is occurring in the human large intestine, principally in the caecum and ascending colon and that the large bowel may have a greater role to play in digestion than has previously been ascribed to it.

Journal Article The control and consequences of bacterial fermentation in the human colon Get access J.H. Cummings, J.H. Cummings Medical Research Council, Dunn Clinical Nutrition Centre, Cambridge, UK Dr J.H. Cummings, Medical Research Council, Dunn Clinical Nutrition Centre, 100 Tennis Court Road, Cambridge CB2 1QL, UK. Search for other works by this author on: Oxford Academic Google Scholar G.T. Macfarlane G.T. Macfarlane Medical Research Council, Dunn Clinical Nutrition Centre, Cambridge, UK Search for other works by this author on: Oxford Academic Google Scholar Journal of Applied Bacteriology, Volume 70, Issue 6, 1 June 1991, Pages 443–459, https://doi.org/10.1111/j.1365-2672.1991.tb02739.x Published: 01 June 1991 Article history Accepted: 03 November 1990 Published: 01 June 1991

A procedure is described for the measurement and characterisation of total non-starch polysaccharides in plant foods by gas-liquid chromatography of individual sugars as alditol acetates. Starch, including that resistant to gelatinisation in boiling water, is dispersed with dimethyl sulphoxide and then hydrolysed with α-amylase and pullulanase. Starch-free material is hydrolysed with sulphuric acid and the released neutral sugars are measured as alditol acetates by using N-methylimidazole in order to catalyse the acetylation. Uronic acids are measured by a spectrophotometric method. The procedure is a modification of a more comprehensive method reported previously. It is relatively rapid and simple compared with gravimetric procedures, is applicable to a wide range of foodstuffs, can be carried out without special expertise in carbohydrate chemistry and is suitable for routine laboratory use.