Diabetes Doctor Rancho Cucamonga – Dr. Cora Lanyon, D.C.
The Glycemic Index (GI) is a relative ranking of carbohydrate in foods according to how they affect blood glucose levels.
Carbohydrates with a low glycemic index of 55 or below causes a slower rise in the blood glucose and insulin values in the type 2 patient with diabetes. All major diabetes organizations from around the world now recommend use of the glycemic index ranking system in the meal planning control aspect of glucose management in diabetes control.
How is the Glycemic Index (G.I.) Measured?
Fifty grams of digestible carbohydrate are fed to ten different people and then the effect on their blood glucose is then measured over the next two hours. This is called the international standard method. For each person the area under the curve is measured for this test food. On another occasion the same ten people consume an equal amount of glucose and a curve is measured as for the test food and this is called the reference value. A GI value for the test food is then calculated for each person by dividing their glucose AUC for the test food by their glucose AUC for the reference food. The final GI value for the test food is the average GI value for the 10 people. This system has been in existence since 2002 and has been researched extensively with positive results for its use in lowering blood glucose values and stabilizing insulin levels.
What is the Glycemic Index Diet?
This diet focuses on carbohydrates, with the goal of eating foods that produce a steady rise in blood sugar instead of the spike in blood sugar created by eating foods that are quickly digested. An additional benefit of the diet is the high fiber content that increases the feeling of fullness with resulting weight loss.
Foods on the Glycemic Index Diet are scored on a scale of 0 to 100 based on how much they raise your blood sugar level. The scale is divided into three sections:
High G.I. Foods: (with scores of 70 or higher) white bread, pasta, crackers, sugar, sweetened soda
Medium G.I. Foods: (scores of 56-69) spaghetti, rice, potatoes, corn, ice cream
Low G.I. Foods: (scores of 55 and under) oatmeal, peanuts, peas, carrots, kidney beans, hummus, skim milk and most fruits
*Glucose has a G.I. of 100 for comparison purposes.
Factors That Impact on the Index Value of a Food
There are many factors that can change the G.I. of a food:
- The type of sugar: The G.I. for fructose is 19 but 105 for maltose. Sugars can readily be recognized by the -ose on the end of the word such as sucrose, lactose, isomaltose, etc.
- Structure of the starch: Starch is composed of two molecules, amylopectin and amylose. Foods with a higher amylose level will have a lower G.I.
- How refined the carbohydrate is: The more processed a food is, the higher the G.I.
- Nutrient Composition: Both fat and acid will slow down food transit and lower the G.I. Adding a little avocado, olive oil, or lemon juice will lower the G.I. of a meal.
- Cooking method: In general, the longer the food is cooked the more broken down and available starch becomes thus increasing the G.I.
Amount of carbohydrates play a role in G.I.
The rate at which foods raise blood sugar levels depends on three factors:
- the type of carb they contain,
- the nutrient composition,
- the amount you eat.
Research has shown that following a low glycemic index diet can yield better glycemic control in type 2 diabetes and is cardioprotective when it comes to diabetic comorbidities. According to a recent Cochrane review, complications can be reduced by as much as 20% with better glycemic control and reduction of HbA1C through following this meal plan approach.
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