What is the Glycemic Index?

Question: What is the Glycemic Index?

Some low carb diets (such as South Beach) rely on the glycemic index as a way to decide which foods to choose. The glycemic index sounds complicated, but it's just a way of getting an idea of how a food is likely to affect blood sugar. This FAQ tells what factors in a food affect its glycemic index, and why glycemic index might not be the best way to look at the affect of foods on blood sugar.

Answer: Carbohydrate is not all created equal – even with equal amounts of carbohydrate, some foods will cause a higher blood sugar rise than others. The higher the glycemic index (GI), the higher the glucose response in the blood. Many low carb diets take glycemic index and/or glycemic load into account when making diet recommendations, aiming to avoid a large blood sugar rise.

Some factors that affect GI: Processing (puffed cereals have a much higher GI than the grain they came from), ripeness of fruit (unripe bananas can have a GI of 43, where overripe ones have been clocked at 74), protein content (soy beans have a lower GI than other beans), fat content (peanuts have a very low GI), fiber (orange juice has a higher GI than oranges), and how small the particles are (whole grains have a relatively low GI, but grinding them into flour shoots up the GI).

One criticism of the glycemic index is that since it the scale was created on a standard amount of carbohydrate per food (50 grams), it doesn’t give people information about the amount of food they are actually eating.

A common example is carrots. Carrots do have a high glycemic index, but to get 50 grams of carbohydrate from carrots, you have to eat 4 cups of chopped carrot. For this reason, the concept of the glycemic load was created, which takes serving size into account.

Related Question: Is the Glycemic Index Useful?

List of Foods and Their Glycemic Index

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