The glycemic index (GI) is a method of ranking carbohydrates based on their effect on blood glucose levels in the body. Whilst this effect will slightly differ from person to person, it is a good indicator of how different carbohydrate foods and drinks will affect blood sugar levels in the body.

Low GI carbohydrate foods are absorbed more slowly and cause a steady rise and fall in blood glucose levels and more sustained energy. A low GI diet is recommended for overall good health, weight maintenance and type 2 diabetes management. High GI carbohydrate foods, on the other hand, will typically cause blood glucose levels to rise and fall quickly whereas. This is why after eating a high GI carbohydrate meal we generally feel a burst of energy, followed by a feeling of sluggishness and fatigue. 

What are some factors that affect the glycemic index of foods?

There are several factors that will change the GI value of the foods we consume. These include the chemical makeup and physical structure of the carbohydrates, how refined the carbohydrates are and other nutrients in the food or meal.

In general, the more refined or processed a carbohydrate is, the more quickly and easily it is absorbed by the body. The carbohydrates will be swiftly broken down by digestive enzymes into glucose and rapidly absorbed into the bloodstream to be transported throughout the body.

Different types of carbohydrates will be processed by the body in different ways depending on their glycemic index. Fructose, for example, isn’t as easily metabolised by the body as sucrose (table sugar) which is why fructose has a lower glycemic index than sugar.

What is the glycemic index of sugar?

It’s a common misconception that sugar has a high glycemic index. In fact, sugar (sucrose) has a medium GI of 65. Sucrose is only 50% glucose, with the other 50% being fructose, which is why it has only a moderate effect on blood glucose levels. The GI of various other sugars are listed below in comparison to sugar:

Are there any low GI sweetener options?

The GI of a sweetener will depend on the amount of glucose it contains. Sweeteners with a low proportion of glucose will generally have a lower GI. Fructose, for example, has a low glycemic index of around 23 as it doesn’t increase blood glucose like other carbohydrates and sugars.

Non-sugar sweeteners like erythritol, xylitol, and sorbitol, have little to no effect on blood sugar levels as they do not contain any glucose. They can therefore be considered low GI.

We rarely eat sugars and sweeteners alone, so it’s important to consider the food as a whole including all the carbohydrates and other nutrients it contains which may alter the glycemic index. For example, a cake made with a lower GI sweetener and high GI refined flour would still have a moderate to high GI overall.

Low GI Sugar

There are low GI sugars available for sale that use new technology to help lower its glycemic index naturally. One way this can be done is by coating the raw sugar crystals with a molasses extract which increases the resistance of the sugar crystals to digestion, thus lowering its glycemic index. Low GI sugar has a glycemic index of around 55. 

REFERENCES

• Atkinson FS, Foster-Powell K & Brand-Miller JC. (2008). International table of glycaemic index and glycaemic load values: 2008. Diabetes Care, 31(12):2281–2283
• The University of Sydney Glycemic Index. GI Database. Available at: https://www.glycemicindex.com/foodSearch.php
• Glycemic Index Foundation. How GI is measured. Available at: https://www.gisymbol.com/how-is-gi-measured/ 
• Augustin LSA, Kendall CWC, Jenkins DJA, et al. (2015). Glycemic index, glycemic load and glycemic response: An International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC).  Nutr Metab Cardiovasc Dis, 25(9):795-815