The glycemic index (GI) is a number associated with a particular type of food that indicates the food's effect on a person's blood sugar level. A value of 100 represents the equivalent amount of pure glucose.
The glycemic index of a food is defined as the incremental area under the two-hour blood glucose response curve AUC following a 12-hour fast and ingestion of a food with a certain quantity of available carbohydrate (usually 50 g). The AUC of the test food is divided by the AUC of the standard (either glucose or white bread, giving two different definitions) and multiplied by 100. The average GI value is calculated from data collected in 10-20 human subjects. Both the standard and test food must contain an equal amount of available carbohydrate. The result gives a relative ranking for each tested food.