Glycemic index
Introduction
The Glycemic Index (GI) is a numerical system that measures how much of a rise in circulating blood sugar a carbohydrate causes—the higher the number, the greater the blood sugar response. It is a tool that has been used for decades to monitor the effects of carbohydrate consumption on blood glucose levels.
History
The concept of the glycemic index was developed in 1981 by Dr. David Jenkins and colleagues at the University of Toronto. It was introduced as a method of classifying carbohydrate-containing foods, based on their potential to increase blood sugar levels.
Glycemic Index Scale
The glycemic index scale ranges from 0 to 100. Foods with a high GI (greater than 70) cause a rapid increase in blood glucose levels, while foods with a low GI (less than 55) cause a slower, more sustained increase in blood glucose levels.
Determining Glycemic Index
The glycemic index of a food is determined by feeding a portion of the food containing 50 grams of available carbohydrate (excluding fiber) to a group of healthy people. The blood glucose levels of the test subjects are then measured over the next two hours. These values are then compared to the response of the same group of people to 50 grams of pure glucose, which is set at 100.
Factors Influencing Glycemic Index
Several factors can influence the glycemic index of a food, including the type of carbohydrate, the cooking process, the degree of processing, and the presence of other substances that can slow digestion such as fiber and fat.
Glycemic Index and Health
The glycemic index has been used in dietary planning to help manage conditions such as diabetes and metabolic syndrome. Some studies have suggested that a low-GI diet may aid weight loss and improve lipid profiles, although the evidence is not conclusive.
Criticisms of the Glycemic Index
Despite its widespread use, the glycemic index has been criticized for a number of reasons. These include the fact that the GI of a food can vary depending on how it is prepared and the individual's response to that food. Furthermore, the GI does not take into account the amount of carbohydrate consumed.