What is the glycemic index?The glycemic index gives us an idea of which foods raise our blood glucose fastest and highest.
Why is this important?Many people have problems processing large increases in blood glucose. (See What is Insulin Resistance? and The Road to Diabetes)
What do the numbers mean?Eating pure glucose is given a ranking of 100 -- all other foods are in relation to this. So a food with a glycemic index of 95 raises blood sugar almost as much as pure glucose, but a food with a glycemic index of 20 doesn't raise blood sugar much at all. It's important to keep in mind, though, that the glycemic index does not take portion size into account. The actual amount any food raises blood sugar has to do both with how glycemic it is, and how much of it you eat. The glycemic load attempts to combine these concepts, and some diets are using the glycemic load for this reason.
Why is there such a large range of numbers on many foods?Many factors influence how foods test, including differences between the people tested, the recipes, the laboratory techniques, and the fact that no two carrots are exactly alike.
When there is a single number after a food, that means that only one study was done of that food (it could have been a study from anywhere in the world). That number is an average of the all the individuals in the study, and so you have to think of that number as an estimate. For example, there was a study of Fruit Loops cereal, and the range among the people tested was between 60 and 78, although the result reported was a single number, 69.
When there is a range of numbers after a food, that is the highest and lowest value from different studies. In some cases, averages have been done of several studies, which are also included. But the number for each of those studies was an average of the people in the study.
Because there is so much variation between foods and between individuals, there is essentially no difference between foods that have a difference of less than at least 5 or 10 points on the glycemic scale.
Why are you telling me all this? Can't you just give me a number, like all the other sites? It's too confusing!Although I think the concept of the glycemic index is very useful, I think it's important to educate people about the actual reality of the index if they are going to base their eating around it. And the reality is that no one number tells the tale for any one food in any given body. The only way to truly tell how a food affects you is to check your own blood glucose. That said, the glycemic index can give us some general information about carbohydrates.
Glycemic Index List
Fructose 12-25, average 19, but please read this before using fructose
Glucose 85-111, average 100
Glucose consumed with 15-20 grams of fiber 57-85
Glucose consumed with protein and fat 56
Honey 32-87, average 55
Sucrose (granulated table sugar) most 58-65, 2 studies much higher, bringing the average to 68 (sucrose is half glucose and half fructose)
For glycemic index of sugar alcohols such as maltitol, see chart on this page.
Milk, regular (full fat) 11-40, average 27
Milk, skim - 32
Yogurt without added sugar - 14-23