March 03, 2025 The glycemic index and you

Why is pasta that is cooked al dente (slightly undercooked or still has a bite) better for you than fully cooked pasta? Well, at least one reason has to do with the glycemic index (GI). This measures how much carbohydrate foods raises your blood sugar (glucose) levels compared to a standard food like white bread. Undercooked pasta has a low GI as it takes longer to digest, causing less of a spike in blood sugar after eating. Overcooked pasta is easier to digest and so may have a higher GI, which can raise your blood sugar levels rapidly. 

It has been more than 40 years since University of Toronto researcher Dr. David Jenkins and fellow University of Toronto researcher Dr. Thomas Wolever PhD developed the idea of the glycemic index. While it is vital for people living with diabetes, experts believe that choosing lower GI carbohydrates is important for everyone.

Cayla Runka, a manager on our knowledge & connection team here at Diabetes Canada, says,

A low-GI diet has been linked with improved blood sugar and blood cholesterol levels, which is good for people with type 1 or type 2 diabetes.

She also points to a low-GI diet’s ability to help you feel full faster and longer after eating. And if you are more satisfied after a meal, you are less likely to snack or eat larger portions, making for easier control of blood sugar. Runka adds, “It is essential to keep in mind that even though a food may have a low GI, portions are still important.”

Lighten your load

So does that mean you have to avoid high-GI foods? Not at all. The GI of the food, whether low GI or high GI, can change based on the serving size eaten, cooking method and by combining the food with other ingredients in a meal or snack. By pairing a high GI food with a combination of non-starchy vegetables, lean protein and healthy fats at each meal or snack, you can reduce the overall glycemic response. This concept is known as the glycemic load (GL) and is about the whole of the meal or snack you’ve just eaten and not just the individual foods impact on blood sugar.

Another example? Cooking and cooling potatoes, rice, pasta and other grains and enjoying them cold or reheated once chilled can lower their glycemic response. This is due to the starch molecules bonding together while cooling, which is known as retrogradation. This increases resistant starch which is not digested and so has a lower effect on blood sugar. Resistant starch also provides a bonus of acting as food for healthy gut bacteria and thus improving your gut health.

Measure your progress

Checking your blood sugar after a meal can provide valuable insight into how your food choices may be affecting your diabetes control. Since every body is different, you may find that some low GI foods have a higher affect than expected and some high GI foods have a minor effect on blood sugar.

Foods that work for you

Here are three ways to lower your blood sugar levels and glycemic load:

1. Choose longer-cooking, whole grains. For example, steel cut or large flake oats have a low GI, while instant oats have a high GI value. Runka says, “Choosing a high-GI cereal will produce a greater rise in blood sugar than a low-GI cereal; however, the addition of protein and fibre can help reduce that load. So you can continue to enjoy your favourite foods just be sure to add milk, some high-fibre berries and a few tablespoons of nuts or seeds for protein to balance the bowl. Simple changes like this can make a big difference.”

2. Select coarse breads with grains that you can see rather than light fluffy varieties. And again, choosing one to two slices along with a source of protein like eggs, cheese or meat can help the overall glycemic load of the carbohydrate food. 

3. Add more low-GI pulses—such as dried peas, beans and lentils —at meals, especially when the meal includes a high-GI food. The fibre and protein found in pulses give them a glycemic advantage and help slow the digestion of other higher carbohydrate foods in the meal. The result, a slower and lower blood sugar response. 

Making balanced choices

In general, most high-fibre fruits and vegetables have a low GI. Choose low- and medium-GI foods more often. When enjoying high-GI choices, remember to keep portions in check. Use the Glycemic Index chart as a guide to help you make healthy choices.

The Glycemic Index (GI)

Recipes

Classic chili con carne
Garam masala chicken with ginger rice and garlic spinach
Spinach & mushroom barley pilaf

Did you know?

Want to learn about type 2 diabetes management? Our free year-long online program includes on-demand videos and live sessions that dive deeper into specific topics and Q&As with our diabetes experts. Upcoming bonus sessions will focus on nutrition claims, exercising at home and complications. Visit Virtual Diabetes Education Program to learn more.

This updated article originally appeared in Diabetes Dialogue.