Volume 90, Issue 5, November (2003), pp. 853-864 © The Author 2003
doi:10.1079/BJN2003972

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Postprandial carbohydrate metabolism in healthy subjects and those with type 2 diabetes fed starches with slow and rapid hydrolysis rates determined in vitro

Chris J. Seal¹, Mark E. Daly², Lois C. Thomas², Wendy Bal², Anne M. Birkett³, Roger Jeffcoat³, John C. Mathers^2
1Human Nutrition Research Centre, School of Agriculture, Food and Rural Development, Faculty of Science, Agriculture and Engineering, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, , UK
²School of Clinical Medical Sciences, Faculty of Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, , UK
³National Starch and Chemical Company, 10 Finderne Avenue, Bridgewater, NJ 08807, USA

 (Received 22 April 2002–Revised 30 June 2003–Accepted 4 July 2003)

The objective of the present study was to investigate the effects of starches with differing rates of hydrolysis on exposure to pancreatin in vitro on postprandial carbohydrate metabolism in healthy subjects and in subjects with type 2 diabetes. Two test starches, prepared from uncooked native granular starch products, and naturally enriched with ¹³C, were consumed in a randomized crossover design by eight healthy and thirteen type 2 diabetic subjects. One starch was characterized in vitro as being rapidly hydrolysed (R, 94 % after 180 min), and the other was more slowly hydrolysed (S, 51 % after 180 min). Each subject consumed 50 g of each test starch. In addition, the type 2 diabetic subjects consumed 89·7 g of the S starch on a separate occasion. Blood samples were taken at 10 min intervals for 3 h, and at 20 min intervals for a further 3 h during a 6 h postprandial period. Breath ¹³CO₂ enrichment was measured at the same time points, and indirect calorimetry was performed for seven 20 min sessions immediately before and during the 6 h postprandial period. With the R starch, plasma glucose concentrations and serum insulin concentrations rose faster and the maximum glucose change was approximately 1·8 times that for the S starch, averaged across both subject groups. The areas under the curves for glucose and insulin were, respectively, 1·7 and 1·8 times higher for the R starch compared with the S starch, averaged across both subject groups. The rate of ¹³CO₂ output and the proportion of ¹³C recovered in breath after consumption of the R starch was similar for both subject groups. The results provide evidence that starches which have different rates of hydrolysis in vitro result in different patterns of glycaemia and insulinaemia in both healthy adults and in diet-controlled type 2 diabetic subjects. Data from the hydrolysis of novel starch products in vitro, therefore, are useful in predicting glycaemic responses in vivo.

Keywords:
Starch digestion, Glycaemia: Insulinaemia, In vitro starch hydrolysis, Diabetes

Abbreviations:
GI, glycaemic index, IAUC, incremental area under the curve, NEFA, non-esterified fatty acids, R, rapidly hydrolysed, S, slowly hydrolysed