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How to Use the Glycemic Index

Some foods can make your blood sugar shoot up very fast. That's because carbohydrates like refined sugars and bread are easier for your body to change into glucose, the sugar your body uses for energy, than more slowly digested carbs like those in vegetables and whole grains. Eat a lot of those easy carbohydrates and you'll have a hard time controlling your blood sugar, even with insulin and diabetes medications.

The glycemic index gives you a way to tell slower-acting "good carbs" from the faster "bad carbs." You can use it to fine-tune your carb-counting and help keep your blood sugar more steady.

What Is the Glycemic Index?

Glycemic index is a number. It gives you an idea about how fast your body converts the carbs in a food into glucose. Two foods with the same amount of carbohydrates can have different glycemic index numbers.

The smaller the number, the less impact the food has on your blood sugar.

  • 55 or less = Low (good)
  • 56- 69 = Medium
  • 70 or higher = High (bad)

Look for the glycemic index on the labels of packaged foods. You can also find glycemic index lists for common foods on the Internet. Harvard University has one with more than 100. Or ask your dietitian or nutrition counselor.

Foods that are close to how they're found in nature tend to have a lower glycemic index than refined and processed foods.

Glycemic Index Can Change

That number is a starting point on paper. It could be different on your plate, depending on several things.

Preparation. Fat, fiber, and acid (such as lemon juice or vinegar) lower the glycemic index. The longer you cook starches like pasta, the higher their glycemic index will be.

Ripeness. The glycemic index of fruits like bananas goes up as they ripen.

Other foods eaten at the same time. Bring down the overall glycemic index of a meal by combining a high-glycemic index food with foods that have lower ones.

Your age, how active you are, and how fast you digest food also affect how your body reacts to carbs. If you have a diabetes complication called gastroparesis, which delays your stomach from emptying, your body will absorb food much more slowly.

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