Hostname: page-component-7c8c6479df-r7xzm Total loading time: 0 Render date: 2024-03-28T02:31:57.776Z Has data issue: false hasContentIssue false

Effect of blood sampling schedule and method of calculating the area under the curve on validity and precision of glycaemic index values

Published online by Cambridge University Press:  09 March 2007

Thomas M. S. Wolever*
Affiliation:
Department of Nutritional Sciences, University of Toronto, and Glycaemic Index Testing, Inc., Toronto, Ontario, Canada
*
Corresponding author: Dr Thomas M. S. Wolever, fax +1 416 978 5882, email thomas.wolever@utoronto.ca
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

To evaluate the suitability for glycaemic index (GI) calculations of using blood sampling schedules and methods of calculating area under the curve (AUC) different from those recommended, the GI values of five foods were determined by recommended methods (capillary blood glucose measured seven times over 2·0 h) in forty-seven normal subjects and different calculations performed on the same data set. The AUC was calculated in four ways: incremental AUC (iAUC; recommended method), iAUC above the minimum blood glucose value (AUCmin), net AUC (netAUC) and iAUC including area only before the glycaemic response curve cuts the baseline (AUCcut). In addition, iAUC was calculated using four different sets of less than seven blood samples. GI values were derived using each AUC calculation. The mean GI values of the foods varied significantly according to the method of calculating GI. The standard deviation of GI values calculating using iAUC (20·4), was lower than six of the seven other methods, and significantly less (P<0·05) than that using netAUC (24·0). To be a valid index of food glycaemic response independent of subject characteristics, GI values in subjects should not be related to their AUC after oral glucose. However, calculating GI using AUCmin or less than seven blood samples resulted in significant (P<0·05) relationships between GI and mean AUC. It is concluded that, in subjects without diabetes, the recommended blood sampling schedule and method of AUC calculation yields more valid and/or more precise GI values than the seven other methods tested here. The only method whose results agreed reasonably well with the recommended method (ie. within ±5 %) was AUCcut.

Type
Research Article
Copyright
Copyright © The Nutrition Society 2004

References

Allison, DB, Paultre, F, Goran, MI, Poehlman, ET & Heymsfield, SB (1995) Statistical considerations regarding the use of ratios to adjust data. Int J Obes 9, 644652.Google Scholar
Bland, JM & Altman, DG (1986) Statistical methods for assessing agreement between two methods of clinical measurement. Lancet i, 307310.CrossRefGoogle Scholar
Brand Miller, J, Foster-Powell, K, Wolever, TMS & Colagiuri, S (2002) The New Glucose Revolution: The Authoritative Guide to the Glycemic Index. New York: Marlowe & Company.Google Scholar
Brand Miller, JC, Hayne, S, Petocz, P & Colagiuri, S (2003) Low-glycemic index diets in the management of diabetes: a meta-analysis of randomized controlled trials. Diabetes Care 26, 22612267.CrossRefGoogle ScholarPubMed
Food and Agriculture Organization (1998) Carbohydrates in Human Nutrition. Report of an FAO/WHO Expert Consultation on Carbohydrates, April 14–18, 1997. Rome, Italy, Rome: FAO.Google Scholar
Frost, G, Leeds, A, Trew, G, Margara, R & Dornhorst, A (1998) Insulin sensitivity in women at risk of coronary heart disease and the effect of a low glycemic index diet. Metabolism 47, 12451251.CrossRefGoogle Scholar
Gannon, MC & Nuttall, FQ (1987) Factors affecting interpretation of postprandial glucose and insulin areas. Diabetes Care 10, 759763.CrossRefGoogle ScholarPubMed
Gannon, MC, Nuttall, FQ, Westphal, SA, Neil, BJ & Seaquist, ER (1989) Effects of dose of ingested glucose on plasma metabolite and hormone responses in type II diabetic subjects. Diabetes Care 12, 544552.CrossRefGoogle ScholarPubMed
Ha, M-A, Mann, JI, Melton, LD & Lewis-Barned, NJ (1992) Calculation of the glycaemic index. Diabetes Nutr Metab 5, 137139.Google Scholar
Jenkins, DJA, Wolever, TMS, Taylor, RH et al. (1981) Glycemic index of foods: a physiological basis for carbohydrate exchange. Am J Clin Nutr 34, 362366.CrossRefGoogle Scholar
Jenkins, DJA, Wolever, TMS, Kalmusky, J et al. (1987) Low-glycemic index diet in hyperlipidemia: use of traditional starchy foods. Am J Clin Nutr 46, 6671.CrossRefGoogle ScholarPubMed
Liu, S, Willett, WC, Stampfer, MJ et al. (2000) A prospective study of dietary glycemic load, carbohydrate intake and risk of coronary heart disease in US women. Am J Clin Nutr 71, 14551461.CrossRefGoogle ScholarPubMed
Meyer, KA, Kuski, LTH, Jacobs, DR et al. (2000) Carbohydrates, dietary fiber, and incident type 2 diabetes in older women. Am J Clin Nutr 71, 921930.CrossRefGoogle ScholarPubMed
Salmeron, J, Ascherio, A, Rimm, EB et al. (1997 a) Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care 20, 545550.CrossRefGoogle ScholarPubMed
Salmeron, J, Manson, JE & Stampfer, MJ (1997 b) Dietary fiber, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. J Am Med Assoc 277, 472477.CrossRefGoogle ScholarPubMed
Snedecor, GW & Cochran, WB (1980) Statistical Methods, 7th ed. Ames, IA: Iowa State University Press.Google Scholar
Van Dam, RM, Visscher, AW, Feskens, EJ, Verhoef, P & Kromhout, D (2000) Dietary glycemic index in relation to metabolic risk factors and incidence of coronary heart disease: the Zutphen Elderly Study. Eur J Clin Nutr 54, 726731.CrossRefGoogle ScholarPubMed
Vorster, HH, Venter, CS & Silvis, N (1990) The glycaemic index of foods: a critical evaluation. S Afr J Food Sci Nutr 1, 1317.Google Scholar
Wolever, TMS (1989) How important is prediction of glycemic responses? Diabetes Care 12, 591593.CrossRefGoogle ScholarPubMed
Wolever, TMS (1992) Glycemic index vs glycemic response: non-synonymous terms. Diabetes Care 15, 14361437.CrossRefGoogle Scholar
Wolever, TMS & Jenkins, DJA (1986) The use of the glycemic index in predicting the blood glucose response to mixed meals. Am J Clin Nutr 43, 167172.CrossRefGoogle ScholarPubMed
Wolever, TMS, Jenkins, DJA et al. (1990) Glycemic index of foods in individual subjects. Diabetes Care 13, 126132.CrossRefGoogle ScholarPubMed
Wolever, TMS & Mehling, C (2002) High-carbohydrate–low-glycaemic index dietary advice improves glucose disposition index in subjects with impaired glucose tolerance. Br J Nutr 87, 477487.CrossRefGoogle ScholarPubMed
Wolever, TMS, Vorster, HH, Björk, I (2003) Determination of the glycaemic index of foods: interlaboratory study. Eur J Clin Nutr 57, 475482.CrossRefGoogle ScholarPubMed