An introduction to the glycaemic index (GI)

Definition | The importance of GI for diabetics | Glycaemic load (GL) and response (GR) | Conclusion

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Definition

The glycaemic index (GI), often written ‘glycemic index’, helps us identify foods that are likely to cause spikes in our blood glucose levels. More specifically, it is a numerical ranking system that measures how quickly and dramatically foods containing available, or digestible, carbohydrates raise blood glucose levels when compared to a reference food (usually pure glucose). Those available carbohydrates include simple carbohydrates such as fructose, sucrose, lactose, and glucose but also more complex ones such as starch. Available carbohydrates get digested and absorbed by your body and are used for energy.

On a scale from 1 (low) to 100 (high), 100 equalling the fast-acting glucose, the index tells us when a food’s potential to raise our blood glucose levels quickly is low (1 to ≤ 55), elevated (56 to 69), or high (above 70).

In simpler terms, high-GI foods can lead to a rapid increase in blood glucose levels after eating, often followed by a subsequent ‘sugar crash’. This happens because the carbohydrates are broken down very quickly and released into the bloodstream as glucose.

Foods with a low GI, on the other hand, are broken down more slowly by the body causing the release of glucose into the bloodstream to be more gradual. Those foods often combine more complex carbohydrates with fibre or resistant starches, which are non-available or indigestible carbohydrates. This combination can slow down the digestion and absorption of available carbohydrates, thereby lowering the glycemic index.

However, two things will need to be kept in mind when using the glycaemic index for guidance. The first is that the GI of the same food can be different depending on its ripeness, how it is prepared, and with what other foods it is combined. The second point is that two different individuals will never react alike to the same food. The glycaemic index should therefore be taken as a reference not instructions.

The importance of GI for diabetics

For individuals living with type 1 (T1D) and type 2 (T2D) diabetes, the glycemic index can be a helpful guide. It aids in choosing foods that will not cause immediate blood sugar spikes but rather help maintain blood sugar at a more steady and manageable level.

But please be careful: If you find yourself having a hypo, sticking with foods that quickly and easily release glucose into your bloodstream like fruit juices, is safest. Please talk to your diabetes specialist before making any changes to your diet.

There are multiple reasons why we want to avoid glucose spikes. Diabetic or not. In her book “The Glucose Revolution,” Jessie Inchauspé discusses the adverse effects of blood sugar spikes and advocates for eliminating them from our daily lives. According to her, short-term effects include constant hunger, cravings, chronic fatigue, poor sleep, migraines, memory issues, and challenges in managing T1D. Long-term impacts encompass skin problems, arthritis, Alzheimer’s disease, mental health issues like depression, gut and heart problems, fatty liver, and insulin resistance.

If we can avoid blood sugar spikes and manage more stable blood sugar levels through diet, we are rewarded with greater well-being in the short term and better overall health in the long run. Specifically for type 2 diabetes and prediabetes, as this kind is heavily based on lifestyle and often a lack of weight management, choosing foods low on the GI scale can help regulate appetite and prevent sudden hunger spikes. Thus eating a low GI diet can lead to more sustained energy levels and increased feelings of fullness over a longer time.

Glycaemic load (GL) and Glycaemic response (GR)

Two more important concepts that are often discussed together with GI are glycaemic load (GL) and glycaemic response (GR). While the glycaemic index (GI) ranks foods based on how quickly they raise blood sugar levels, GL paints a more complete picture by taking into consideration the quantity of carbohydrates consumed.

Formula to calculate glycaemic load: GL = (GI x Carbohydrate content in grams per serving) / 100

The glycaemic response pertains to how an individual’s body reacts to carbohydrate-rich foods in relation to blood sugar levels. It is influenced by factors such as the food’s composition, preparation method, and an individual’s metabolism. Components like fiber, fat, and protein content can impact the glycaemic response of a food.

Conclusion

The glycaemic index is a valuable concept in the field of nutrition that can help individuals make informed choices about the types of carbohydrates they consume. Used mindfully and healthily, it can help manage weight and blood sugar levels. Please bear in mind, however, that the tool does have its limitations.
The index only looks at individual foods and doesn’t consider the overall nutritional value of a meal. Also, individual responses to specific foods can vary, making the GI value a useful guideline, not an absolute rule.

Incorporating low-GI foods into diets helps maintain stable energy levels, aids in weight management, regulates blood sugar, and may improve overall health.