In this article I want to explain how the glycemic index, glycemic load and insulin index work.
The glycemic index and glycemic load are variables measured in carbohydrate foods, that evaluate how much they raise blood glucose levels. The insulin index measures the effect on blood insulin levels.
These are often used by diabetic patients to control blood glucose levels.
Personally I think that diabetics would do better by skipping high carbohydrate foods altogether and choose a low-carb, ketogenic diet and Steve Cooksey the Diabetes Warrior is a living example of that.
The Glycemic Index
The glycemic index is simply a measurement of how quickly a carbohydrate food raises blood sugar, compared to the same amount of glucose.
The amount measured is the area under the “two hour curve” when blood glucose is measured for two hours after a meal. The bigger the area, the faster that particular carbohydrate raises blood sugar.
If a food has a high glycemic index (GI), it means that the food is digested and turned into blood sugar quickly. If it has a low GI, it happens slowly.
The way the scale works, is that 50 grams of glucose is assigned a GI score of 100. Then other foods are measured and compared to glucose. For example a food that raises blood sugar 40% as much as glucose is assigned a score of 40.
Many things can affect the glycemic index of a food. For example, it will be lower if consumed with fat or fiber. It will also depend on the individual, and the ripeness and cooking method of the food.
Foods with a lower glycemic index (fruit, whole grains) tend to be healthier than foods with a higher glycemic index (candy, white bread), and eating foods with a low GI is correlated with improved health. This has a lot of exceptions though.
The Glycemic Index Scale:
- Low: 55 or less
- Medium: 56-69
- High: 70 or higher
Check out this database if you want to find the glycemic index or glycemic load of particular foods.
The Glycemic Load
Another system known as the Glycemic Load (GL) is much better for predicting blood glucose levels after meals, because it also incorporates serving sizes.
It is simple to figure out the Glycemic Load if you already know the GI of a food and its carbohydrate content. You multiply the Glycemic Index with the amount of carbohydrate in grams, and divide by 100.
Glycemic Load (GL) = Glycemic Index (GI) * Carbs in grams / 100
For example apples with a GI of 40 and a carb count of 16 grams: GL = (40 * 16) / 100 = 6.4
Therefore foods with a high GI and/or high carb content have a higher glycemic load, while foods with a low GI and/or low carb content have a lower glycemic load.
The Glycemic Load Scale:
- Low: 10 or less
- Medium: 11-19
- High: 20 or higher
The Insulin Index
The Insulin Index measures blood levels of insulin after meals.
These levels are usually correlated with glucose levels, with some exceptions. Some protein containing foods such as beef can cause a higher insulin response than certain carbohydrate containing foods.
The Insulin Index measures the insulin response to various foods, relative to the insulin response to white bread, which is assigned a score of 100.
A food that raises insulin more than white bread has a score over 100, while a food that raises insulin less than white bread has less than hundred.
Some examples: porridge with an insulin index of 40, much less than white bread. Potatoes with 121, higher than white bread and beef with a score of 51 which is less than white bread but higher than porridge.