Glycemic Index: a measure of a carbohydrate’s impact on blood glucose levels

Dr. David Jenkins at the University of Toronto developed the glycemic index to more accurately describe how different carbohydrates affect blood sugar levels.  The higher the glycemic index value the more easily a given carbohydrate is metabolized into glucose and the greater the resulting insulin response.

White bread or glucose is used as the reference food where the glycemic index for each is set at 100.  It’s important to know which reference is used when comparing glycemic index numbers because the white bread based glycemic index value will be higher for a given carbohydrate than the glucose based glycemic index.  To convert the white bread based glycemic index reference value to the glucose based glycemic index reference you multiply by 0.7 (the glycemic index of white bread is 70 on the glucose reference based standard).  To avoid any confusion I will only use the glucose reference standard.¹

High glycemic foods (65 and above) include things you would expect like jelly beans (78) but also items you may not expect such as baked potatoes (85) and white bread (70).  In this example “complex” carbohydrates such as potatoes can have a greater impact on blood sugar than “simple” sugars such as found in jelly beans.