Overview
ISO 26642:2010 - Food products - Determination of the glycaemic index (GI) and recommendation for food classification - specifies a standardized in vivo method to determine the glycaemic index (GI) of carbohydrates in foods. The standard defines GI, sets qualifying factors for valid application, details experimental and analytical requirements, and recommends criteria for classifying foods as low, medium or high GI (see Annex B).
Key topics and technical requirements
- Definitions and concepts: GI, glycaemic carbohydrate (available carbohydrate), non-glycaemic carbohydrate, incremental area under the curve (IAUC) and blood glucose response.
- Carbohydrate portion: Test portions are based on either 50 g of glycaemic carbohydrate or 25 g where a 50 g portion is impractical.
- Reference food: Glucose (GI = 100) is the primary reference; alternatives (e.g., standardized white bread) may be used if cross‑verified and results expressed relative to glucose.
- Study subjects and ethics:
- Minimum of 10 healthy subjects with specified inclusion/exclusion criteria.
- Ethics committee approval and informed consent required.
- Pre-test restrictions (fasting ≥10 h, no alcohol prior evening, no vigorous exercise).
- Testing and analytical procedure:
- In vivo GI testing using blood glucose responses measured over 2 hours post‑ingestion.
- IAUC calculated (trapezoid rule) and GI expressed as percent of reference IAUC.
- Reference food tested at least twice (preferably three) per subject within the test window.
- Mean within‑subject coefficient of variation (CV) for reference food should be ≤ 30% (with limited allowance for outliers).
- Qualifying factors and re‑testing:
- GI applies only to the specific food in the physical state consumed.
- Re-testing indicated when macronutrient composition, processing, osmolality, acidity or other key factors change.
Applications and users
ISO 26642:2010 is intended for practical and research use by:
- Food manufacturers (product formulation and validated GI labelling)
- Testing laboratories and accreditation bodies (method implementation and quality control)
- Regulators and policy makers (nutrition claims and standards enforcement)
- Research organizations and educational institutes (clinical and nutritional studies)
Practical uses include validated GI measurement for product claims, product development to lower post‑prandial glycaemic impact, clinical nutrition research, and standardized data for dietary guidance.
Related standards and references
- Developed by ISO/TC 34 (Food products) and references Joint FAO/WHO expert consultation on carbohydrates in human nutrition.
- Cites related ISO guidance such as ISO 3534‑1:2006 (statistics) and ISO 5725‑1:1994 (accuracy of measurement methods).
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