Backgrounds

Before understanding the significance of the glycemic index on health especially for diabetics, few important terminologies should be clear.

These terminologies are; 

  • Glycemic index (GI);
  • Glycemic response (GR);
  • Glycemic load (GL)

What is glycemic index ?

The glycemic index is a physiological assessment of the quality of carbohydrates based on their direct effect on blood glucose levels 2 hours after the meal.

What is glycemic response ?

Glycemic response is the increase in the blood glucose concentration following eating and stated as the incremental area-under-the-blood-glucose-curve (iAUC) for two hours. In short, it is the appearance of glucose in the bloodstream following eating.

Glycemic response is a normal physiological incidence that depends on the degree of glucose entry into the circulation (i.e the amount of glucose absorbed), the rate of glucose disappearance from the circulation because of tissue uptake, and hepatic regulation of glucose release.

What is glycemic load?

The concept of glycemic load takes account of the glycemic index of a food and the amount is eaten. The glycemic load is gained by multiplying the quality of carbohydrates in a given food (GI) by the amount of carbohydrate in a serving of that food.

In short, dietary glycemic load is the sum of the glycemic loads for all foods consumed in the diet.

Significance of the glycemic index

The classification of foods based on the glycemic index has been used as a measure to estimate the probable prevention and treatment strategies for diseases where glycemic control is very crucial, such as diabetes

It has been scientifically proven that fiber-rich foods generally have a low glycemic index, at the same time not all foods with a low glycemic index essentially have high fiber content.

Numerous health benefits of low glycemic index, high-fiber diets have been proven, along with lower postprandial glucose level and insulin responses, and an improved lipid profile due to reduced insulin resistance.

What is glycemic index of foods?

Based on the glycemic index values, foods can be divided into three categories. Below is the name of those three categories with the names of some commonly used foods;

  • Low GI (1 to 55): Carrots, green peas, soybeans, green vegetables, most fruits, nuts (almonds, peanuts, pecans, sunflower seeds, hazelnuts, olives walnuts).
  • Medium GI (56 to 69): Banana, oatmeal, sweet potato, white rice,  raw pineapple, raisins, grapes, nuts (cashews and macadamia)
  • High GI (70 to 100): Pure sugar, white potato, whole wheat bread, brown rice, white bread, corn flakes, Honey, Corn syrup, watermelon, Processed Foods, Sugary Drinks.

If someone is aiming for a low-glycemic-index diet, they should focus on whole grains, fruits, vegetables, and legumes and should avoid the high-glycemic-index food items such including processed foods.

Items such as dairies like cow milk, frozen yogurt, soya-milk, yogurt as well as almond milk are low-glycemic-index foods whereas rice milk comes under the high-glycemic-index category.

Non-vegetarian foods such as meat, poultry, and fish do not have a glycemic index, because they do not contain carbohydrates. Many of the times these foods come under low-glycemic-index categories.

What is glycemic load of foods?

The glycemic load can be calculated by multiplying the glycemic index by the amounts of available carbohydrates (g) and dividing the total by 100.

The glycemic load can be divided into three categories;

  • Low GL (1 to 10): Watermelon, Bread, white-wheat flour, Table sugar, Honey, Apple, syrup, Pear, Cashews, Peanuts, Kidney bean
  • Medium GL (11 to 19): Banana, Pineapple, Soda crackers, Doughnut, Puffed rice cakes
  • High GL (20 or more): Potato, Cornflakes, Pancake, white and brown Rice, Dates,

This can be straightforwardly understood by the following example. An apple has a glycemic index of 40 and contains 15 grams of carbohydrates. Thus the glycemic load will be =(40 x 15)/100 = 6.  Since Apple has a glycemic load of 6, so is considered a low-glycemic-load food.

Benefits of low glycemic index foods

Foods with a lower glycemic index have several health benefits such as;

  • Minimized the risk for type 2 diabetes
  • Lower the risk of cardiovascular diseases
  • Lower the cholesterol level
  • Make the body sensitive and to produce more insulin

What are the other factors which affect GI of foods?

  • Methods of cooking: frying, boiling, and baking.
  • Processing of food also modifies the glycemic index.
  • Fiber contents.
  • Fat lowers the GI of a food-Frying high GI food in fat reduces its GI.
  • Protein lowers the GI of food.

The glycemic index diet and type 2 diabetes?

Foods having lower GI cause low or no rise in blood sugars at the same time eating of foods with a high glycemic index may result in a rapid increase in blood sugar levels.

Currently available pieces of evidence suggest that substituting high carbohydrates with low carbohydrates glycemic index reduces the risk of developing Type 2 diabetes. Adopting the Glycemic Index Diet can also be beneficial for Type 1 diabetes to manage their blood sugar levels.

Take home message for diabetics

Based on the knowledge of the glycemic index, Diabetics should follow these recommendations;

  • Low GI (Green = Go), Choose more often and eat freely
  • Medium GI (Yellow = Caution) Choose less often and often restricted
  • High GI (Red = think) Stop and preferred to avoid and prohibited

Reference

  • Wolever TM. The glycemic index. World Rev Nutr Diet. 1990;62:120-85. PMID: 2180214.
  • Esfahani A, Wong JM, Mirrahimi A, Srichaikul K, Jenkins DJ, Kendall CW. The glycemic index: physiological significance. J Am Coll Nutr. 2009 Aug;28 Suppl:439S-445S. doi: 10.1080/07315724.2009.10718109.
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