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GI Determination

The standard GI determination protocol requires that ten normal subjects are studied on multiple occasions (maximum 3 per week) in the morning after an overnight fast. After 2 fasting blood samples are taken, subjects eat a test meal containing 50g available carbohydrate and have further blood samples taken at 15, 30, 45, 60, 90 and 120 minutes after starting to eat. Capillary blood is obtained by finger-prick and whole blood glucose determined on-site in our laboratory with an automatic analyzer using the glucose oxidase method.

Each subject conducts one trial of each test food and 3 trials of the reference food. The reference food can be anhydrous glucose or white bread, analyzed so its composition is exactly known, and baked in our test kitchens. If large numbers of foods are being tested, a reference food trial should be done for every 6-7 test foods. This ensures that there are no changes in subject's glucose responses with time.

Blood samples are analyzed in our laboratory by our specially-trained technicians. The resulting glucose values are used to calculate the Glycemic Index.

Our GI determination protocol fully complies with ISO/FDIS 26642, the Final Draft of the International Standard for GI determination, as well as the Standards Australia GI determination protocol.

In addition to standard GI protocol, we have also developed protocols for situations where foods are not appropriate for GI testing or a direct comparison of different ingredients is desired.One of our senior scientists would be pleased to discuss your specific requirements to determine the most appropriate test method for your product(s).

GI Labs is an accredited laboratory for the Glycemic Index Symbol Program.