Editing Glycemic index (section)

==Measurement==
The glycemic index of a food is defined as the incremental area under the two-hour blood glucose response curve ([[Area under the 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 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.<ref name="glycemic1"/><ref>{{cite journal |vauthors=Brouns F, Bjorck I, Frayn KN, etal |title=Glycaemic index methodology |journal=Nutr Res Rev |volume=18 |issue=1 |pages=145–71 |date=June 2005 |pmid=19079901 |doi=10.1079/NRR2005100 |doi-access=free }}</ref>

Foods with carbohydrates that break down quickly during digestion and release glucose rapidly into the [[bloodstream]] tend to have a high GI; foods with carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, tend to have a low GI.

A lower glycemic index suggests slower rates of digestion and absorption of the foods' carbohydrates and can also indicate greater extraction from the liver and periphery of the products of carbohydrate digestion.{{citation needed|date=May 2022}}

The current validated methods use glucose as the reference food, giving it a glycemic index value of 100 by definition. This has the advantages of being universal and producing maximum GI values of approximately 100. White bread can also be used as a reference food, giving a different set of GI values (if white bread = 100, then glucose ≈ 140). For people whose [[Staple food|staple]] carbohydrate source is white bread, this has the advantage of conveying directly whether replacement of the dietary staple with a different food would result in faster or slower blood glucose response. A disadvantage with using white bread as a reference food is that it is not a well-defined reference: there is no universal standard for the carbohydrate content of white bread.{{cn|date=January 2025}}