Original Communication

European Journal of Clinical Nutrition (2003) 57, 475–482. doi:10.1038/sj.ejcn.1601551

Determination of the glycaemic index of foods: interlaboratory study

T M S Wolever1, H H Vorster2, I Björck3, J Brand-Miller4, F Brighenti5, J I Mann6, D D Ramdath7, Y Granfeldt3, S Holt4, T L Perry6, C Venter2 and  Xiaomei Wu3

  1. 1Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
  2. 2Department of Nutrition and Family Ecology, Potchefstroom University for Christian Higher Education, South Africa
  3. 3Chemical Centre, Department of Applied Nutrition and Food Chemistry, University of Lund, Lund, Sweden
  4. 4Human Nutrition Unit, Department of Biochemistry, University of Sydney, Sydney, Australia
  5. 5Human Nutrition Unit, Department of Public Health, University of Parma, Italy
  6. 6Department of Human Nutrition, University of Otago, Dunedin, New Zealand
  7. 7Biochemistry Unit, Department of Preclinical Sciences, University of the West Indies, Trinidad and Tobago

Correspondence: T M S Wolever, Department of Nutritional Sciences, University of Toronto, Toronto, Canada MSS 3E2. E-mail: thomas.wolever@utoronto.ca

Guarantor: TMS Wolever.

Contributors: TMSW coordinated the study, did the statistical analysis and drafted the manuscript. TMSW and HHV conceived of the overall study and were responsible for raising funds and planning the studies at their local sites. IB, JBM, FB, JIM and DDR (whose names are listed in alphabetical order) were responsible for raising funds and planning the studies at their local sites. YG, SH, TLP, CV and XW were responsible for implementing the studies at their local sites. All contributors helped with the revision of the paper.

Received 4 October 2001; Revised 10 June 2002; Accepted 11 June 2002.

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Abstract

Objective: Practical use of the glycaemic index (GI), as recommended by the FAO/WHO, requires an evaluation of the recommended method. Our purpose was to determine the magnitude and sources of variation of the GI values obtained by experienced investigators in different international centres.

Design: GI values of four centrally provided foods (instant potato, rice, spaghetti and barley) and locally obtained white bread were determined in 8–12 subjects in each of seven centres using the method recommended by FAO/WHO. Data analysis was performed centrally.

Setting: University departments of nutrition.

Subjects: Healthy subjects (28 male, 40 female) were studied.

Results: The GI values of the five foods did not vary significantly in different centres nor was there a significant centretimesfood interaction. Within-subject variation from two centres using venous blood was twice that from five centres using capillary blood. The s.d. of centre mean GI values was reduced from 10.6 (range 6.8–12.8) to 9.0 (range 4.8–12.6) by excluding venous blood data. GI values were not significantly related to differences in method of glucose measurement or subject characteristics (age, sex, BMI, ethnicity or absolute glycaemic response). GI values for locally obtained bread were no more variable than those for centrally provided foods.

Conclusions: The GI values of foods are more precisely determined using capillary than venous blood sampling, with mean between-laboratory s.d. of approximately 9.0. Finding ways to reduce within-subject variation of glycaemic responses may be the most effective strategy to improve the precision of measurement of GI values.

Keywords:

carbohydrates, diet, methods, blood glucose responses

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