Glycemic Index

The glycemic index (GI) represents the total rise in a person's blood sugar level after consumption of a specific food.

The glycemic index is measured following a 12-hour fast and ingestion of a food with a fixed amount of available carbohydrate (usually 50 g). It is measured from the incremental area under the two-hour blood glucose response curve. As the GI of food is calculated relative to the equivalent of 50 g glucose, it typically ranges between 50 and 100. For example, the glycemic index of pure glucose is defined as 100.

The GI is useful for understanding how the body breaks down carbohydrates and only takes into account the available carbohydrate (total carbohydrates excluding fibers) in a food. Increase in blood sugar can be influenced by a number of other factors, such as the quantity of fat eaten with the food.

The GI does not take the quantity of food into account, but only the carbohydrates contained. A related measure, the glycemic load, factors the quantity of food in by multiplying the glycemic index of the food in question by the carbohydrate content of the actual serving. Carrots have a high glycemic index, but a low glycemic load for the quantity typically consumed. Fructose, by contrast, has a low glycemic index, but can have a high glycemic load if a large quantity is consumed.

The impact of different food on the blood glucose level is very important for diabetics.