About Glycemic Index

About Us

Welcome to the 'home of the glycemic index' - the official website for the glycemic index and international GI database which is based in the Human Nutrition Unit, School of Molecular Bioscience, University of Sydney. The website is updated and maintained by the University's GI Group which includes research scientists and dietitians working in the area of glycemic index, health and nutrition including research into diet and weight loss, diabetes, cardiovascular disease and PCOS and headed by Professor Jennie Brand-Miller. Each month the Group publishes a free e-newsletter, GI News, to bring consumers and health professionals up to date with the latest GI research from around the world.

The glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health. Low GI diets have been shown to improve both glucose and lipid levels in people with diabetes (type 1 and type 2). They have benefits for weight control because they help control appetite and delay hunger. Low GI diets also reduce insulin levels and insulin resistance.

Recent studies from Harvard School of Public Health indicate that the risks of diseases such as type 2 diabetes and coronary heart disease are strongly related to the GI of the overall diet. In 1999, the World Health Organisation (WHO) and Food and Agriculture Organisation (FAO) recommended that people in industrialised countries base their diets on low-GI foods in order to prevent the most common diseases of affluence, such as coronary heart disease, diabetes and obesity.

American Diabetes Association 2006
Practical Use of the GI
Johanna Burani, MS, RD, CDE
(2.2 MB)
Powerpoint presentation

Measuring the GI

To determine a food's GI value, measured portions of the food containing 50 grams of available carbohydrate (or 25 grams of available carbohydrate for foods that contain lower amounts of carbohydrate) are fed to 10 healthy people after an overnight fast. Finger-prick blood samples are taken at 15-30 minute intervals over the next two hours. These blood samples are used to construct a blood sugar response curve for the two hour period. The incremental area under the curve (iAUC) is calculated to reflect the total rise in blood glucose levels after eating the test food. The GI value is calculated by dividing the iAUC for the test food by the iAUC for the reference food (same amount of glucose) and multiplying by 100 (see Figure 1). The use of a standard food is essential for reducing the confounding influence of differences in the physical characteristics of the subjects. The average of the GI ratings from all ten subjects is published as the GI for that food.

The GI of foods has important implications for the food industry. Some foods on the Australian market already show their GI rating on the nutrition information panel. Terms such as complex carbohydrates and sugars, which commonly appear on food labels, are now recognised as having little nutritional or physiological significance. The WHO/FAO recommend that these terms be removed and replaced with the total carbohydrate content of the food and its GI value. However, the GI rating of a food must be tested physiologically and only a few centres around the world currently provide a legitimate testing service. The Human Nutrition Unit at the University of Sydney has been at the forefront of glycemic index research for over two decades and has tested hundreds of foods as an integral part of its program. Jennie Brand Miller is the senior author of International Tables of Glycemic Index published by the American Journal of Clinical Nutrition in 1995 and 2002 and by Diabetes Care in 2008.

GI Graph

Glycemic Index Books

Jennie Brand-MillerJennie Brand-Miller is one of the world's leading authorities on the glycemic index. She and her co-authors have published a number of practical books on how choosing low GI carbohydrates - the ones that produce smaller fluctuations in your blood glucose and insulin levels - is one of the secrets to long-term health, reducing your risk of diabetes and heart disease. It is also one of the keys to sustainable weight loss. Their books, which appeal to both consumers and health professionals, include The Diabetes and Pre-diabetes Handbook, The New Glucose Revolution, The Low GI Diet, Low GI Eating Made Easy, The Shopper's Guide to GI Values, The Low GI Guide to Your Heart and Metabolic Syndrome, The Low GI Guide to Managing PCOS and the fully illustrated in colour Low GI Diet Cookbook and Low GI Vegetarian Cookbook. The success of these books along with this website and database have generated an increased demand for GI testing by SUGiRS - Sydney University's commercial testing laboratory with an enviable reputation for quality, speed and flexibility.

Glycemic Index Symbol Program

The GI Symbol Program was launched in Australia in 2002 to help consumers identify the GI of foods. Foods that carry the symbol are guaranteed to have been properly tested by an accredited laboratory.

In the near future, many more foods are likely to carry the GI on their nutrition panel. The services of a professional GI testing service such as SUGiRS will therefore allow food companies to take advantage of GI marketing opportunities.