A good guide to good carbs: The glycemic index

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, well, 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.

The rise of blood sugar levels

High glycemic foods result in a quick spike in insulin and blood sugar (also known as blood glucose). Low glycemic foods have a slower, smaller effect.

Using the glycemic index

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, low-fat 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.

You can see the values for 100 commons foods and get links to more at

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

For more on healthy diet essentials plus information on managing (and avoiding) Type 2 diabetes, buy Healthy Eating for Type 2 Diabetes by Harvard Medical School.