Healthbeat

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 www.health.harvard.edu/glycemic.

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

Cornflakes

Bran flakes

Baked potato

Pasta, bulgur

White bread

Whole-grain bread

Corn

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.