Glycemic index (GI) is a measure of how quickly a food can make your blood sugar (glucose) rise. Only foods that contain carbohydrates have a GI index. Foods such as oils, fats, and meats do not have a GI index.
In general, low GI foods increase glucose slowly in your body. Foods with a high GI increase blood glucose quickly.
If you have diabetes, high GI foods can make it harder to control diabetes.
Not all carbohydrates work the same in the body. Some trigger a quick spike in blood sugar, while others work more slowly, keeping blood sugar more even. The glycemic index addresses these differences by assigning a number to foods that reflects how quickly they increase blood glucose compared to pure glucose (sugar).
The GI scale goes from 0 to 100. Pure glucose has the highest GI and is given a value of 100.
Eating low GI foods can help you gain tighter control over your blood sugar. Paying attention to the GI of foods can be another tool to help manage diabetes, along with carbohydrate counting. Following a low-GI diet also may help with weight loss.
Glycemic Index of Certain Foods
Low GI foods (0 to 55):
- Bulgar, barley
- Pasta, parboiled (converted) rice
- High-fiber bran cereal, steel-cut or rolled oatmeal
- Carrots, non-starchy vegetables, greens
- Apples, oranges, grapefruit, and many other fruits
- Most nuts, legumes, and beans
- Milk and yogurt
Moderate GI foods (56 to 69):
- Pita bread, rye bread
- Brown rice
High GI foods (70 and higher):
- White bread and bagels
- Most processed cereals and instant oatmeal
- Most snack foods
- White rice
Meal Planning with the Glycemic Index
When planning your meals:
- Choose foods that have a low to medium GI.
- When eating a high GI food, combine it with low GI foods to balance the effect on your glucose levels. The GI of a food changes when you combine it with other foods.
The GI of a food is affected by certain factors, such as the ripeness of a piece of fruit. So you need to think about more than the GI of a food when making healthy choices. When choosing meals, it's a good idea to keep these issues in mind.
- Portion size still matters because calories still matter, and so do carbohydrates. You need to keep an eye on the portion size and number of carbs in the meal you are having, even if it has low GI foods.
- In general, processed foods have a higher GI. For example, fruit juice and instant potatoes have a higher GI than whole fruit and whole baked potato.
- Cooking can affect the GI of a food. For example, al dente pasta has lower GI than soft-cooked pasta.
- Foods higher in fat or fiber tend to have a lower GI.
- Certain foods from the same class of foods can have different GI values. For example, converted long-grain white rice has a lower GI than brown rice. And short-grain white rice has a higher GI than brown rice. Likewise, quick oats or grits have high a GI but whole oats and whole-grain breakfast cereals have a lower GI.
- Choose a variety of healthy foods keeping in mind the nutritious value of the whole meal as well as the GI of foods.
- Some high GI foods are high in nutrients. So balance these with lower GI foods.
For many people with diabetes, carbohydrate counting along with choosing healthy foods and maintaining a healthy weight are enough to control diabetes and lower the risk for complications. But it you have trouble controlling your blood sugar or want tighter control, you may want to talk with your health care provider about using the glycemic index as part of your action plan.
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Review Date 11/6/2016
Updated by: Emily Wax, RD, The Brooklyn Hospital Center, Brooklyn, NY. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.