Glycemic index
From ArticleWorld
The glycemic index is a method of ranking carbohydrates based on their effect on blood glucose levels. Dr. David J. Jenkins developed the glycemic index with his colleagues at the University of Toronto in 1981.
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Definition
A food's glycemic index is tested by measuring the area under the two-hour blood glucose response curve (also known as the AUC) after the ingestion of a portion of carbohydrate. The AUC of the test food is then divided by the AUC of the standard food (which is typically either glucose or white bread) and then it is multiplied by 100. The GI value is collected in 10 human subjects and then the average is calculated. For testing purposes, both the standard and the test food must have the same amount of carbohydrate. The result of this formula is a relative ranking of the food.
Glycemic indices
The carbohydrates with the highest glycemic indices are those that break down rapidly in the digestion process. Carbohydrates that have a slow breakdown and release glucose slowly into the blood stream are the ones with the lowest glycemic indices. Therefore, a lower GI indicates slower digestion and slower sugar/starch absorption. It also can indicate greater extraction from the liver. A low GI means a lower demand for insulin and thereby better long-term blood glucose control.
Categories
GI values for food can be interpreted based on this scale:
- Low GI-less than 55.
- Intermediate-55-69.
- High GI-Greater than 70.
Health
A low GI food is appropriate for diabetics, dieters and endurance athletes since it releases food slowly and steadily. Meanwhile, a high GI food is ideal for post-endurance exercise and recovery since it provides a rapid rise in the level of blood sugars. Some scientific evidence shows that those who follow a low GI diet over the course of several years are put at a lower risk of type 2 diabetes and coronary heart disease. Also, animal research that has been conducted recently indicates that a high GI diet puts one at a greater risk of obesity.
Criticism
Critics of the glycemic index say that the GI of food depends on the kind of food, storage methods, preparation methods and ripeness. They also say that the GI varies from person to person and even as much as day to day in an individual and that the GI of a meal made up of many foods is hard to predict.