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What is the Glycemic Index?


Updated June 10, 2014

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

  1. About.com
  2. Health
  3. Low Carb Diets
  4. Low Carb 101
  5. Frequently Asked Questions
  6. Basic Information About the Glycemic Index with Links to More

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