Glycemic index calculation

What is the glycemic index and how it is calculated

A simple but understandable definition of a glycemic index could be the following:

the glycemic index (IG) expresses the capacity of the carbohydrates contained in foods to raise the blood sugar level.

However, this definition does not refer to the methods used to calculate the glycemic index of a given food. For this reason, a more elaborate definition is generally found in books dedicated to human nutrition:

the Glycemic Index of a given food is defined as the incremental area subtended by the glycemic curve, caused by the intake of a 50 g portion of food carbohydrates, expressed as a percentage of the incremental area subtended by the glycemic curve, caused by the intake of 50 g of glucose from the same subject.

This definition, apparently incomprehensible, is actually more complete and correct than the previous one. To fully understand it, it is necessary to understand the experimental method used to calculate the glycemic index of a food.

Fasting blood glucose is measured for an individual or a sample of people. They are then asked to take 50 grams of glucose, and then evaluate their blood sugar at regular time intervals.

Collecting these data allows you to plot the glycemic variations in relation to the passage of time in a graph. The area subtended by this line is given the value 100, since glucose is the reference food for assessing the glycemic index of other foods.

Each individual is then given a certain amount of food, calculated to provide exactly 50 grams of available carbohydrates. In this way you put yourself in the same conditions as the previous test and you can make a correct comparison between the two foods.

Similarly to what has been done for glucose, the glycemic values are then measured at regular time intervals. After having reported the data in the usual graph, the evaluation of the relationship between the extension of the two areas, will allow to calculate the glycemic index of the food.