Puzzled by the Glycemic Index?
Read These FAQs.

What is the Glycemic Index (GI)?

It is a measurement of how foods impact the level of glucose in the blood. Refined carbs like flour, sugar, and corn syrup yield are high GI foods; while fibrous carbohydrates, proteins and fat are (mostly) lower GI foods.

Why is this Index considered important?

Some researchers believe that a diet with high GI foods can provoke post-prandial (“after meal”) hyperglycemia, which can cause problems because, in response to high blood sugar levels, the body tends to produce surges of insulin.

How do people measure the GI?

They use a curve called the AUC to quantitatively describe how much blood sugar will be released by the eating of a particular food.

For instance, if you eat a bowl of pasta, your blood sugar levels will spike right afterwards and then decrease as your body metabolizes the pasta. If you sum up the area under the AUC curve, you'll get the Glycemic Index for that meal.

How are foods classified according to the GI?

Nutritionists use either glucose or white bread to "zero out" the scale. When glucose is used, it's measured at 100. When white bread is used, the bread is considered 100, while glucose is considered 140. Nutritionists typically classify low GI foods as 55 or less and high GI foods as 70 or more.

What can influence the Glycemic Index?

Lots of factors, apparently, including:

• The amount of fiber in a food.
• The amount of vinegar in a food.
• The inclusion or exclusion of protein and fat in a meal.
• The time of day the food is eaten.
• The amount of stress you’re under when you eat.
• The reactions of an individual’s metabolism to a particular food.

Are there potential problems with the GI approach?

Perhaps. There's evidence to suggest that measuring the insulin response a food provokes may be more important than measuring GI.

What are examples of high and low GI foods?

Low GI foods include: meat, shellfish, butter, vegetables, and whole-grain breads.

High GI foods include: white rice, glucose, and fruit juices.

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