Glycemic index is a measure of how quickly a carbohydrate containing food is broken down and absorbed into the bloodstream. The time it takes for a food to be absorbed is measured on a scale from 0 to 100. For example, glucose is a carbohydrate in its purest form, and is absorbed the fastest so it’s given the highest value of 100.
Glycemic Index (GI):
Low GI: 1 to 55
Medium GI: 56 to 69
High GI: 70 and higher
“While glycemic index can tell us how quickly a food is absorbed, it doesn’t tell us how much your blood sugar increases.”
Glycemic load:
Glycemic load is a measure that takes into account the amount of carbohydrate in a portion of food together with how quickly it raises blood glucose levels.
GL = GI x amount of carbohydrate / 100
Low Glycemic load: 0 to 10
Medium Glycemic load: 11 to 19
High Glycemic load: 20 and over
Glycemic index vs. glycemic load: is one better than the other?
Glycemic load is a better tool to measure a food’s impact on blood glucose and insulin response than glycemic index alone because it also considers the amount of carbohydrate in a portion.
For example, watermelon has a GI value of 76 (High GI) but one serving of watermelon (1 cup of cubed fruit) only has 11 grams of carbohydrates because it’s mostly water. If we calculate the GL = (76 x 11 grams carbohydrate) / 100), we get a value of 8, making it a low-GL food. So eating a serving of watermelon isn’t actually going to have a big effect on your glucose levels.
Glycemic Index and the effect on insulin sensitivity:
However, eating too many high-GI foods over time can impair insulin sensitivity. If insulin is constantly being released to absorb large amounts of glucose, it loses its effectiveness.
In addition to eating foods with soluble fiber, another strategy is pairing a carbohydrate with a fat or protein, two nutrients that help to slow glucose absorption (fibres, fats and proteins decrease GI of food), prevent rapid spikes, and improve satiety.
