I remember several years ago when people started freaking out about eating carrots and grapes because “they have so much sugar in them!” It’s about the time that the glycemic index became well-known, and we are still battling the effects of what I would call a “partial story”.
The GI of a food is an indicator of how much your blood sugar raises in the 2 hours after you eat an amount of said food that contains 50 grams of carbohydrates. The GI can be from 0 – 100, with white bread being the baseline (with a “perfect” score of 100). So, it’s a comparison scale more so than an absolute number… but the higher the number, the more quickly your blood sugar goes up when you eat enough of the food to ingest 50 grams of carbohydrates.
The problem with the GI index is the use of 50 g of carbohydrate. Sure, carrots have a GI of 70, but you would have to eat 2.5 pounds of carrots to get 50 g of carbohydrate! For reference, that’s about 60 baby carrots. I mean really, I like carrots as much as the next person, but I’m not sitting down and eating 2.5 pounds of them!
This is why the glycemic load is more reasonable. It takes into account the amount of carbohydrate by weight of the food. Sticking with our carrot example, their GI is 70, but their GL is 7… which is considered a low carbohydrate containing food. Ultimately, the GL considers the concentration of carbohydrates in carrots, which is not that high thanks to the water, fiber, vitamins and minerals also contained in them.
(As a side note, I don’t particularly care for either the GI or the GL as a sole evaluator of a food because there seems to be no definitive answer on what the GI or GL is of any food. I found 3 different answers for the GI of carrots ranging from 35 on Harvard’s website to 60 in my school notes to 70 on a nutrition information website. That’s not my idea of good science!)