GLYCEMIC INDEX vs GLYCEMIC LOAD
What is the difference between Glycemic Index of a food and the Glycemic Load of a food?
The glycemic index of a food is a measure of the increase in the level of blood glucose after consuming a food containing a carbohydrate, compared with eating a standard amount of pure glucose (as a control). The foods that are able to be broken down in the small intestine into glucose will affect the glycemic index of that food and are ranked 0-100 (100 being the ranking of pure glucose). Foods that are insoluble fibers (high resistant starches) pass through the small intestine and do not raise blood glucose and are low glycemic. These insoluble fibers/resistant starches then reach the large intestine where the gut bacteria are able to break them down (these foods then resemble a soluble fiber in the large intestine).
The Glycemic Load of a food refers to the amount of available carbohydrate consumed in grams by the rate at which the carbohydrate is metabolized and enters the blood stream as glucose (the glycemic index)by the amount of available carbohydrate in a single serving of that food divided by 100 The glycemic load is calculated by multiplying the GI Glycemic Index of food by the available carbohydrate in that food. As an example, Watermelon’s glycemic load is 72 (glycemic index) x 5 grams of available carbohydrate/100 = 3.6 (LOW Glycemic Load). The glycemic load range is stated as 1-10 Low; 11-19 Medium and 20 and above is high. The available carbohydrate refers to the digestible amount of carbohydrates in the food product. It, therefore, does not include dietary fiber.
When calculating the glycemic index of a food the ISO 26642 protocol requires testing to be conducted having 10 patients eat 50 grams of available carbohydrate of a food product. In order to calculate the amount of a food that will yield 50 grams of available carbohydrate, the available carbs in 1 serving of the food product is divided by the weight in grams of the product. Next divide 50/quotient previously calculated which gives the total number of grams of the food product weight needed to be consumed in order to receive 50 grams of available carbohydrates. For example:a 39 gram cookie (1 serving) has 17 grams of carbohydrates minus 2 grams of fiber =15 grams of available carbohydrates. 15/39 = .385. Next divide 50/.385 = 130 grams of cookie weight needed to be eaten in order to eat 50 grams of available carbohydrates. 130/39 = 3.3 cookies to be eaten for the test.