The Glycemic Index: What’s It All About? 

What is the glycemic index and how does it relate to diabetes management? Our certified diabetes educator breaks it down.

By Susan B. Sloane, BS, RPh, CDE

If you are a person living with diabetes and are working on diabetes management, chances are you’ve heard the term glycemic index before. It can be a confusing and intimidating concept to tackle at first, so let’s try to break it down.

In simple terms, the glycemic index measures the degree to which a variety of carbohydrate-containing foods cause blood sugars to rise after eating them. In general, people with diabetes want to stay “in-range.” This means they want to keep their blood sugar within a certain range set by their health care team, and they should avoid glucose spikes as much as possible. Eating healthy foods with lower glycemic index values is one way to keep blood glucose levels steady.

The glycemic index ranks foods from 1-100, based on how quickly your body converts these foods into glucose. The idea behind a low glycemic diet is to not over-stress the pancreas by making it work too hard. Low glycemic diets have been studied as a way to potentially prevent type 2 diabetes and have seen some interesting results.¹

As a mom with two sons with diabetes, and as someone who has tested blood sugars a lot, I can say firsthand that you can see significant results if you test blood sugars after a meal with high glycemic versus low glycemic foods.

Foods with a glycemic index (GI) under 51 are generally considered to be low glycemic foods; foods with a high GI are foods with a value over 70.² The GI value is calculated by comparing a carbohydrate containing food to a high GI food like white bread, which is often used as a standard of comparison. This fact alone should make you want to avoid white bread whenever possible.

Several factors affect the GI of foods, such as the addition of fiber to the food. Fiber slows down the digestion process and therefore decreases the GI of the food. Cooking will also affect the GI of various foods, especially pasta.

For example, pasta has a GI of between 40 and 50. You can further reduce the GI of pasta by cooking it less. Similarly, if a carbohydrate-containing food has higher levels of fat or acid, it will have a lower GI. That’s why many diets recommend using lemon juice and vinegar to flavor foods.

Some foods have a high glycemic index but do not raise blood glucose that much because their overall carbohydrate content is rather low. For example, watermelon has a relatively high GI (about 80) but because the carbohydrate content is only around 6 grams per serving, it doesn’t raise blood sugars as much as you would think.

This may help to explain why some foods raise blood sugars more than others, and how you can “pair” certain food together to decrease their effect on blood sugar, such as adding lemons or fiber-rich foods to your dishes.

This is a very brief and overall look into glycemic indexes and how they may influence your blood sugar levels. There is a lot of information on the internet regarding this subject, so if you are interested in reading more, don’t hesitate to investigate. Just remember to always be careful of your sources! Also, if you want to check the glycemic levels of different foods, there are many websites that contain specific information about different foods and their unique glycemic indexes.

The more knowledge you have on glycemic indexes and other topics relating to diabetes, the more informed you’ll be when it comes to making decisions regarding your diet and how it will impact your diabetes.