Understanding the Glycemic Index

glycemic index foods

As many of our clients are affected by diabetes, I’ve decided to continue on the diabetes topic today. The glycemic index, or GI, measures how a carbohydrate-containing food raises blood glucose. Glucose or white bread is used as a reference, and foods are ranked based on how they compare to the reference.

A food with a high GI raises blood glucose more than a food with a medium or low GI.

Meal planning with the GI involves choosing foods that have a low or medium GI. If eating a food with a high GI, you can combine it with low GI foods to help balance the meal.

Examples of carbohydrate-containing foods with a low GI include dried beans and legumes (like kidney beans and lentils), all non-starchy vegetables, some starchy vegetables like sweet potatoes, most fruit, and many whole grain breads and cereals (like barley, whole wheat bread, rye bread, and all-bran cereal).

Protein (meat, fish, chicken, eggs etc) and fats do not have a GI because they do not contain carbohydrate.

Examples of foods based on their GI.

Low GI Foods (55 or less)

  • 100% stone-ground whole wheat or pumpernickel bread
  • Oatmeal (rolled or steel-cut), oat bran, muesli
  • Pasta, converted rice, barley, bulgar
  • Sweet potato, corn, yam, lima/butter beans, peas, legumes and lentils
  • Most fruits, non-starchy vegetables and carrots

Medium GI (56-69)

  • Whole wheat, rye and pita bread
  • Quick oats
  • Brown, wild or basmati rice, couscous

High GI (70 or more)

  • White bread or bagel
  • Corn flakes, puffed rice, bran flakes, instant oatmeal
  • White rice, rice pasta, macaroni and cheese from mix
  • Potato, pumpkin
  • Pretzels, rice cakes, popcorn, saltine crackers
  • Melons and pineapple

What Affects the GI of a Food?

Fat and fiber tend to lower the GI of a food. As a general rule, the more cooked or processed a food, the higher the GI; however, this is not always true.

Below are a few specific examples of  factors that can affect the GI of a food:

  • Ripeness and storage time — the more ripe a fruit or vegetable is, the higher the GI.
  • Processing — juice has a higher GI than whole fruit; mashed potato has a higher GI than a whole baked potato, stone ground whole wheat bread has a lower GI than whole wheat bread.
  • Cooking time — how long a food is cooked (al dente pasta has a lower GI than soft-cooked pasta).
  • Variety — converted long-grain white rice has a lower GI than brown rice but short-grain white rice has a higher GI than brown rice.

Remember

Many nutritious foods have a higher GI than foods with little nutritional value. For example, oatmeal has a higher GI than chocolate. Use of the GI needs to be balanced with basic nutrition principles of variety for healthful foods and moderation of foods with few nutrients.