Understanding the glycemic index (GI)

Diabetes Canada recommends people living with diabetes or prediabetes choose lower glycemic index (GI) foods and drinks more often to help control blood sugar. The GI is a scale out of 100 that ranks a carbohydrate-containing food or drink by how much it raises your blood sugar levels after it is consumed. In general, the more highly processed a food is, or the quicker it is digested, the higher the GI. For example, instant oats have a higher GI than steel cut oats.

While individual response to carbohydrate-containing foods may vary, typically foods with a high GI create a higher and faster rise in blood sugar than foods with a low GI. There are three categories:

low GI (55 or less)
medium GI (56-69)
high GI (70 or more)

Aim to eat foods in the low GI category most often as they tend to have less of an effect on blood sugar. Aim to eat foods in the medium category less often, and foods in the high GI category the least often. Work with your registered dietitian to find ways to substitute medium and/or low GI category foods into your meals and snacks, and to learn more about how a mixed meal can impact blood sugar response.

Benefits of a low-glycemic index diet

A low GI diet can help you:

decrease your risk of type 2 diabetes and its complications
decrease your risk of heart disease and stroke
feel full faster and longer
manage your weight

Meal planning ideas

Here are some meal planning ideas to lower the overall GI of a meal:

Cook pasta ‘al dente’ (firm). Since al dente pasta requires more work from the body during digestion, the digestion rate is slower and, therefore, the GI is lower. Check your pasta package instructions for cooking time.
Make fruits and milk part of your meal. These foods often have a low GI.
Try lower GI grains, such as quinoa, barley and bulgur.
Pulses (e.g., dried beans, peas, lentils and chickpeas) are considered part of two categories: starchy foods and protein foods Swap half of your higher GI starch food serving with beans, lentils or chickpeas. For example, instead of having 1 cup of cooked rice, have 1⁄2 cup of cooked rice mixed with 1⁄2 cup of black beans.
Cool red or white potatoes after boiling or baking and enjoy them cold, such as in a potato salad. This increases resistant starch which has a lower effect on blood sugar.

Using the glycemic index to choose foods is just one aspect of healthy eating. Healthy eating also means choosing a variety of foods, having moderate portion sizes, and selecting more whole foods instead of processed foods.

Also, while the glycemic index can indicate the likelihood of a food’s impact on your blood sugar, we don’t often eat individual foods but rather include them as a part of a healthy meal. Because of this, overall meal planning matters and the GI is just one tool to help individuals make healthy choices for their diabetes management.