The Glycemic Index In-depth


By: Karen Davidson

Which of the following statements do you think are true?

  1. Table sugar breaks down slower in the body than a slice of white bread.
  2. Fruit breaks down into sugar slower than instant rice.

If you answered “true” to both of these questions—congratulations! You certainly know a lot about the food you are eating. If you weren’t sure, you may want to learn more about the Glycemic Index.

The Basics of the Glycemic Index

When you eat a food containing carbohydrate (e.g. milk, fruit or a chocolate bar) it gets broken down into sugar (glucose) in your body to provide energy.

The Glycemic Index (GI) is a ranking of such foods on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those which are rapidly converted into sugar and, when absorbed, result in marked fluctuations in blood sugar levels. Foods such as milk, fruit and table sugar tend to have lower-GI values than common starchy foods such as bread, rice, potatoes and breakfast cereals.

Before the development of the GI, scientists assumed that foods containing simple sugars produced rapid increases in our blood-sugar level. This was the basis of the advice to avoid sugar, a prescription revised by the American Diabetes Association and others based on GI data.

The GI is useful to the person with diabetes who wants to minimize the incidence of high blood sugar. Selecting low-GI foods that tend to have more fiber and are low in fat, helps control rises in blood sugar and insulin levels as well as blood lipids.

A listing of the GI for various foods is listed below.

For a more extensive listing of the GI of various foods a searchable database is available at

If you are trying to develop a diet consisting of low-GI foods, consider the following:

  • Select breakfast cereals based on wheat bran, barley and oats
  • Choose whole grain, pumpernickel and oat bran bread more often than white bread
  • Eat pasta, rice, yams, lima beans or baked potatoes more often than mashed, boiled or instant potatoes
  • Eat parboiled, brown or white rice more often than instant rice
  • Eat fruit as they have a low GI
  • Prepare dishes with beans such as chili, soups and salad

GI of Various Foods

High GI Foods Low GI Foods
Food GI Food GI
White bread 100 Pumpernickel bread 66
Melba toast 100 Oat bran bread 72
Corn flakes 119 All-Bran 60
Instant rice 124 Parboiled rice 68
Potato 104 Sweet potato 54
French fries 107 Pasta 40 to 70
Couscous 93 Lentils/kidney/baked beans 40 to 69
Table sugar 83 Apple/banana/plum 34 to 76
Soda crackers 106 Stone wheat thin crackers 67
Ice cream 87 Skim milk 46


Although table sugar can produce a slower rise in blood-glucose levels than potatoes, it lacks the vitamins, minerals and fiber provided by the potato.

Decisions on what foods to eat must be made on the basis of overall nutrition, as well as the impact on blood sugar. Also, don’t forget about the roles that fat and protein will play.

Adding low-fat protein foods and/or heart-healthy fats to meals can also slow down the absorption of carbohydrates.



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