Glycaemic Index Otago
The University of Otago is New Zealand's first accredited glycaemic index testing laboratory.
What is the Glycaemic Index (GI)?
The glycaemic index (GI) is a way of ranking carbohydrate-containing foods according to their effect on blood glucose (sugar) levels compared to a glucose standard following consumption. The glycaemic index classification of foods provides a numerical physiologic classification of carbohydrate foods ranking foods on a scale of 1-100 based on their blood glucose response. The GI of a food can be ranked into low, medium and high (Table 1). For the same amount of carbohydrate, foods with a lower GI will raise blood glucose less than those with higher GI values. In general carbohydrates that breakdown quickly during digestion have the highest glycaemic indexes. The blood glucose response is fast and high. Carbohydrates that breakdown slowly, releasing glucose gradually into the blood stream, have a low glycaemic index. The glycaemic index is becoming an increasingly popular tool by which to make healthy food choices. It can help consumers choose the right type of carbohydrate for their health and lifestyles.
| Table 1. Standard Glycaemic Index Ranking | |
|---|---|
| Glycaemic Index Ranking | Glycaemic Index Range |
| Low GI | 55 or less |
| Medium GI | 56-69 |
| High GI | 70 or more |
How is the GI Measured?
The GI is tested in humans under controlled conditions. To determine a food GI rating, measured portions of the test food containing 50 grams (or 25 grams in some cases) of carbohydrate are fed to 12 healthy individuals after an overnight fast. Three glucose references are also measured on separate occasions using the same procedure as described above. Finger-prick blood samples are taken at 15-30 minute intervals over the following two hours. These blood samples are used to construct a blood glucose response curve for the two-hour period. The area under the curve (AUC) is calculated and reflects the total rise in blood glucose levels after eating the test food. The GI rating (%) of the test food is calculated by dividing the AUC for the test food by the mean AUC for the reference food (glucose) and multiplying by 100. The GI of the test food is the mean ± SEM of the 12 subjects.
How Much Does it Cost to Measure?
Please email us for current pricing structure.
Discount - We will offer a 10% discount when testing 6 or more products. For existing or previous clients, consideration will be given to a reduction in GI testing costs.
How Long Does it Take to Test a Product?
It takes between 1-2 weeks to test one food product. For testing we need to recruit 12 healthy participants, complete testing of the food along with 3 reference glucose tests, and write a report. As we collect blood samples as part of GI testing we need to allow time for study participants to recover between each session.
Contract Agreement and Confidentiality
Before commencing any research project to measure the GI values of foods, we require each company to sign a formal research agreement to confirm conditions under which the research will be carried out and the ownership and use of data produced. This agreement confirms that the research will be conducted in a confidential manner to protect the company's commercial interests. In addition, the payment details and time-line of the research will be specified.
The contract will be emailed to you. Please sign two (2) copies of the contract and post back to
Dr Tracy Perry
Department of Human Nutrition
University of Otago
PO Box 56
Dunedin
NEW ZEALAND
How to Get Products Tested
STEP 1: Please email us us for expression of interest and current pricing structure.
STEP 2: Please sign 2 copies of the contract and post to Dr Tracy Perry.
STEP 3: Complete the submission form and send along with product(s) for testing (as outlined in the submission form) to Dr Tracy Perry.
STEP 4: Product(s) will be tested and a report including the GI value will be posted/emailed to you on completion of testing.
GI Symbol
Our laboratory is accredited by the Sydney University Glycaemic Index Research Service (SUGiRS) for the purposes of GI testing. This means that foods that are tested in our laboratory are eligible for consideration in the GI Symbol Program. The Glycaemic Index Symbol Program provides consumers with an easily recognizable logo that they can trust to make healthier food options. Consumers know that products carrying the GI symbol have been tested appropriately for GI and meet the program's strict nutrient criteria.
Contact Details
Sara Macdonald
Glycaemic Index Otago, Co-ordinator
Email: sara.macdonald@otago.ac.nz
Phone: +64 3 479 5430
Dr Tracy Perry
Email: tracy.perry@otago.ac.nz
Phone +64 3 479 7508
Glycaemic Index Otago
Department of Human Nutrition
University of Otago
PO Box 56
Dunedin
NEW ZEALAND
Tel 64 3 479 5430
Fax 64 3 479 7958