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What Is the Glycemic Index?

Have you noticed that a lot of people these days are talking about eating low on the glycemic index? Depending on your frame of mind, this could be either very annoying or kind of cool. Of course, it’s possible they really don’t know what the heck they’re talking about. So what is the glycemic index (GI)? Here’s a primer.

If you have diabetes, you know all too well that when you eat carbohydrates, your blood sugar goes up. The total amount of carbs you consume at a meal or in a snack mostly determines what your blood sugar will do. But the food itself also plays a role. A serving of white rice has almost the same effect as eating pure table sugar — a quick, high spike in blood sugar. A serving of lentils has a slower, smaller effect.

Picking good sources of carbs can help you control your blood sugar and your weight. Even if you don’t have diabetes, eating healthier carbohydrate-rich foods can help ward off a host of chronic conditions, from heart disease to various cancers to diabetes. One way to choose foods is with the glycemic index (GI). This tool measures how much a food boosts blood sugar.

The glycemic index rates the effect of a specific amount of a food on blood sugar compared with the same amount of pure glucose. A food with a glycemic index of 28 boosts blood sugar only 28% as much as pure glucose. One with a GI of 95 acts like pure glucose.

Using the glycemic index is easy: choose foods in the low GI category instead of those in the high GI category (see below), and go easy on those in between.

  • Low glycemic index (GI of 55 or less): Most fruits and vegetables, beans, minimally processed grains, pasta, dairy foods, and nuts.
  • Moderate glycemic index (GI 56 to 69): White and sweet potatoes, corn, white rice, couscous, breakfast cereals such as Cream of Wheat and Mini Wheats.
  • High glycemic index (GI of 70 or higher): White bread, rice cakes, most crackers, bagels, cakes, doughnuts, croissants, most packaged breakfast cereals.

Swaps for lowering glycemic index

Instead of this high-glycemic index food

Eat this lower-glycemic index food

White rice

Brown rice or converted rice

Instant oatmeal

Steel-cut oats


Bran flakes

Baked potato

Pasta, bulgur

White bread

Whole-grain bread


Peas or leafy greens

You can see the values for 100 commons foods and get links to more at:
Source: Harvard Health Publications