Original Article

European Journal of Clinical Nutrition (2006) 60, 104–112. doi:10.1038/sj.ejcn.1602273; published online 5 October 2005

Determination of glycaemic index; some methodological aspects related to the analysis of carbohydrate load and characteristics of the previous evening meal

Guarantor: Y Granfeldt.

Contributor: YG and XW carried out the experiments and evaluated the results. IB and YG designed the experiments and were responsible for writing the manuscript.

Y Granfeldt1, X Wu1 and I Björck1

1Department of Applied Nutrition and Food Chemistry, Department of Food Technology, Engineering and Nutrition, Lund University, Sweden

Correspondence: Dr Y Granfeldt, Division of Applied Nutrition and Food Chemistry, Department of Food Technology, Engineering and Nutrition, Lund University, PO Box 124, SE-221 00 Lund, Sweden. E-mail: Yvonne.Granfeldt@inl.lth.se

Received 16 August 2004; Revised 7 July 2005; Accepted 1 August 2005; Published online 5 October 2005.

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Abstract

Objectives:

 

To determine the possible differences in glycaemic index (GI) depending on (1) the analytical method used to calculate the 'available carbohydrate' load, that is, using carbohydrates by difference (total carbohydrate by difference, minus dietary fibre (DF)) as available carbohydrates vs available starch basis (total starch minus resistant starch (RS)) of a food rich in intrinsic RS and (2) the effect of GI characteristics and/or the content of indigestible carbohydrates (RS and DF) of the evening meal prior to GI testing the following morning.

Design:

 

Blood glucose and serum insulin responses were studied after subjects consuming (1) two levels of barley kernels rich in intrinsic RS (15.2%, total starch basis) and (2) after a standard breakfast following three different evening meals varying in GI and/or indigestible carbohydrates: pasta, barley kernels and white wheat bread, respectively.

Subjects:

 

Healthy adults with normal body mass index.

Results:

 

(1) Increasing the portion size of barley kernels from 79.6 g (50 g 'available carbohydrates') to 93.9 g (50 g available starch) to adjust for its RS content did not significantly affect the GI or insulin index (II). (2) The low GI barley evening meal, as opposed to white wheat bread and pasta evening meals, reduced the postprandial glycaemic and insulinaemic (23 and 29%, respectively, P<0.05) areas under the curve at a standardized white bread breakfast fed the following morning.

Conclusion:

 

(1) Increasing portion size to compensate for the considerable portion of RS in a low GI barley product had no significant impact on GI or II. However, for GI testing, it is recommended to base carbohydrate load on specific analyses of the available carbohydrate content. (2) A low GI barley evening meal containing high levels of indigestible carbohydrates (RS and DF) substantially reduced the GI and II of white wheat bread determined at a subsequent breakfast meal.

Keywords:

glucose and insulin responses, second-meal tolerance, glycaemic index, methodological aspects, barley, humans

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