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Glycemic index – what is it?


The glycemic (glycaemic) index (GI; /ɡlaɪˈsiːmɪk/[1]) is a number from 0 to 100 assigned to a food, with pure glucose arbitrarily given the value of 100, which represents the relative rise in the blood glucose level two hours after consuming that food.[2] The GI of a specific food depends primarily on the quantity and type of carbohydrate it contains, but is also affected by the amount of entrapment of the carbohydrate molecules within the food, the fat and protein content of the food, the amount of organic acids (or their salts) in the food, and whether it is cooked and, if so, how it is cooked. GI tables, which list many types of foods and their GIs, are available.[3] A food is considered to have a low GI if it is 55 or less; high GI if 70 or more; and mid-range GI if 56 to 69. (Wikipedia)


Foods with carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream tend to have a high GI; foods with carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, tend to have a low GI.


A lower glycemic index suggests slower rates of digestion and absorption of the foods' carbohydrates and can also indicate greater extraction from the liver and periphery of the products of carbohydrate digestion.


The current validated methods use glucose as the reference food, giving it a glycemic index value of 100 by definition. This has the advantages of being universal and producing maximum GI values of approximately 100. White bread can also be used as a reference food, giving a different set of GI values (if white bread = 100, then glucose ≈ 140). For people whose staple carbohydrate source is white bread, this has the advantage of conveying directly whether replacement of the dietary staple with a different food would result in faster or slower blood glucose response. A disadvantage with using white bread as a reference food is that it is not a well-defined reference: there is no universal standard for the carbohydrate content of white bread. Glycemic Index of Certain Foods


Low GI foods (0 to 55):

  • Bulgar, barley

  • Pasta, parboiled (converted) rice

  • Quinoa

  • High-fiber bran cereal

  • Oatmeal, steel-cut or rolled

  • 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

  • Couscous

  • Brown rice

  • Raisins

High GI foods (70 and higher):

  • White bread and bagels

  • Most processed cereals and instant oatmeal, including bran flakes

  • Most snack foods

  • Potatoes

  • White rice

  • Honey

  • Sugar

  • Watermelon, pineapple

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, and its impact on people with diabetes may change 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 does the amount of carbohydrates. You need to keep an eye on the portion size and number of carbohydrates 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 potatoes.

  • 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 a high GI but whole oats and whole-grain breakfast cereals have a lower GI.

  • Choose a variety of healthy foods keeping in mind the nutritional 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, or carb counting, helps limit carbohydrates to a healthy amount. Carb counting along with choosing healthy foods and maintaining a healthy weight may be enough to control diabetes and lower the risk for complications. But if you have trouble controlling your blood sugar or want tighter control, you should talk with your health care provider about using the glycemic index as part of your action plan.

Reference citation:MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); [cited 2023 Dec 26]. Available from: https://medlineplus.gov/.



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