Nutritionists now rate foods according to their glycemic indexes, the amount a food raises blood glucose compared with a benchmark–usually white bread.
An apple, for example, has a glycemic index of 52, which means that 50 grams of carbohydrate in an apple raises blood glucose levels 52 percent as much as 50 grams of carbohydrate in white bread.
Sounds quite scientific and easy to use except for one important fact.
The index is “per 50 grams of carbohydrate” not 50 grams of the food or the “per serving” we are used to seeing as the standard on most nutrition labels.
Researchers were not measuring the quantity of carbohydrate in a food but the impact of that food’s type of carbohydrate on blood glucose.
However, the amount of available carbohydrate in various plant-based foods varies tremendously.
For example, because carrots contain so much water and unavailable carbohydrate in the form of indigestible fiber, to provide 50 grams of available carbohydrate, reserchers had to feed each subject seven full-size carrots.
In contrast, to provide 50 grams of available carbohydrate in spaghetti, they had to feed subjects only a cupful.
Now, when you open the fridge do you grab 7 full size carrots?
7 carrots eaten together have a glycemic index of 68.
A cup of spaghetti has an index of 64.
So, even though almost equal in terms of glycemic index, a cup of spaghetti has 7 times the impact of a carrot on your blood sugar.
Correcting glycemic indexes for serving size exposes refined carbs as the culprits they really are.
Bagels, for example, aren’t just a little worse than carrots, they’re terrible!
You would have to eat 30 raw carrots to get the glucose shock you get from one bagel.
Adjusting a food’s glycemic index based on serving size is called a food’s glycemic load.
Glycemic load, then, is a measure of the effect on blood sugar of a normal serving size of food.
So, if we want to control blood sugar spikes and the body’s insulin response, the glycemic load and not glycemic index of a food is what we need to be concerned with.