What Is the Difference Between Glycaemic Index and Glycaemic Load?

Blood sugar is expected to rise after eating and to return to its normal level about 2 hours after a meal. The nutrient with the greatest effect on blood sugar is carbohydrate. How much a carbohydrate raises blood sugar is described by the concepts of glycaemic index and glycaemic load. Glucose is the most important energy source for all our cells. Because quick and sustained rises in blood sugar increase insulin secretion, eating patterns with a high glycaemic index have been associated with higher rates of obesity, diabetes and related chronic conditions.

What Is the Glycaemic Index (GI)?

The glycaemic index classifies carbohydrate-containing foods according to how quickly they affect glucose levels in the blood. The carbohydrate structures in different foods raise blood sugar to different degrees. Foods are classified as low, medium or high glycaemic index according to the scores they receive on this scale. In general, the more processed a food is, the higher its glycaemic index is expected to be.

What Factors Affect the Glycaemic Index?

The glycaemic index is affected by various factors. These are:

1. Differences in the structure of starch: The starch molecule is made up of two substances called amylose and amylopectin. Amylopectin has a branched structure, while amylose is straight. Depending on the difference in surface area, digestion differs.
2. Dietary fibre: Soluble fibre is known to have a lower glycaemic effect.
3. Non-nutrient substances: This group includes enzyme inhibitors, phytates, lectins, saponins and tannins. These substances affect starch digestion and so lower the GI.
4. The starch-protein relationship: The amount of protein in a food affects the digestion of starch. It is suggested that the protein network reduces the rate at which starch is absorbed in the small intestine.
5. The structure of the food and how it is processed: Foods with whole grains produce a lower glycaemic index response than foods without grains or liquid foods.
6. Eating slowly: Digestion and absorption are slower, so the glycaemic index is thought to be lower.

Glycaemic Index Ranges

The glycaemic index of foods is divided into 3 groups: low, medium and high. These are:

Low (55 or less): Most fruit and vegetables, pulses such as beans and chickpeas, minimally processed grains, pasta, low-fat dairy products and hazelnuts.

Medium (56 to 69): Sweet potato and baked potato, corn, couscous, white sugar, brown rice.

High (70 or more): White bread, white rice, potato, most crackers, simit (Turkish sesame bread ring), cake, sweets, doughnuts, ready-made fruit juices, most packaged breakfast cereals.

Possible Benefits of a Low Glycaemic Index Diet

A low glycaemic index diet has been associated with the following:

1. It may help with sweet cravings and the urge to eat.
2. It may help support steadier blood sugar.
3. It is associated with a lower risk of type 2 diabetes.
4. It may help in preventing obesity.
5. It is associated with a lower risk of heart disease.
6. It may help people with diabetes who use insulin to follow their blood sugar more steadily, with their doctor's guidance.
7. Eating foods with a high fibre content can support bowel movement.
8. It is associated with healthier cholesterol levels.
9. It may help with insulin resistance.

The glycaemic index does not tell us exactly how far our blood sugar can rise after a meal. That is why the concept of glycaemic load is also needed to explain how much blood sugar may be affected after eating.

What Is Glycaemic Load (GL)?

The effect on blood sugar of the amount eaten of a carbohydrate-containing food is called glycaemic load.

Glycaemic Load = (Glycaemic Index x the food's carbohydrate amount) / 100.

Like the glycaemic index, glycaemic load is divided into three groups: low, medium and high. Values of 0-10 mean a low glycaemic load, values of 11-19 a medium glycaemic load, and values of 20 and above a high glycaemic load.

Glycaemic Index and Glycaemic Load Values of Some Foods

This article is for general information only; please consult your doctor and dietitian about your own situation.