How Important Is the Glycemic Index: Diabetes Questions & Answers

Q. How important is it for me to use the glycemic index (GI) when choosing foods? An exercise program I’m involved in says not to eat any foods with a GI over 50, but my diabetes counselor says they’re not looking at the whole picture. Who’s right? And how should I choose which carbohydrate foods to eat?

A. Both are right — to an extent. The glycemic index, or GI, measures how much a carbohydrate-containing food raises your blood glucose level. A food with a high GI raises blood glucose more than a food with a medium or low GI. The presence of fat or fiber in a food tends to lower its GI, largely because they slow the digestive process. Low-GI foods include whole grains, beans, and most vegetables. Choosing only foods that have low GI is one way to keep your blood glucose levels lower after eating.


However, just because a food has a low GI does not mean that the portion size is irrelevant. The amount you eat also affects your post-meal blood glucose level.

Remember, too, that the GI of a food is different when eaten alone than when combined with other foods. We rarely eat a single food at a time. Most meals and snacks involve eating two or more foods. If you are eating a food with a high GI, you can combine it with a low-GI food to help lower the overall GI of the meal or snack.

There is no single diet that works for everyone with diabetes. However, because the type of carbohydrate you eat does affect blood glucose, the glycemic index is another helpful tool to manage diabetes when combined with carbohydrate counting.

Want to learn more about the glycemic index? Read “Glycemic Index Update,” “Glycemic Index and Glycemic Load,” and “Diabetes Meal Planning: Glycemic Index.”