Glycaemic index & glycaemic load - simply explained

A constantly stable blood sugar level keeps us from cravings, supports our energy level and our performance. But what foods can we eat to keep insulin levels low, and how can we avoid a sharp rise in blood sugar? What is the glycaemic index, and how do you calculate the glycaemic load? All these questions will be answered in this blog post, because glycaemic index tables and the connection to glycaemic load serve as a basic basis for a conscious diet without extreme blood sugar reactions.

 

What are the benefits of the Glyx Diet & what are the benefits of a low glycaemic index?

The Glyx diet aims to keep blood sugar stable while avoiding high insulin secretion. Fewer blood sugar fluctuations and lower insulin secretions - the sugar storage hormone - has many physiological advantages: Energy lows and cravings can be avoided and the hormonal system is relieved and brought into balance, which counteracts overweight, improves well-being and sleep, and weight loss also works more purposefully without the compulsion to constantly resist cravings.
Why the Glyx concept alone does not necessarily lead to success, however, and why other factors must be taken into account in order to avoid a sharp rise in blood sugar, is explained in more detail later in here.

 

What is a high glycaemic index?

The glycaemic index (GI) shows the effect of 50g of carbohydrates of a respective food on the blood sugar level. Simple sugar in the form of glucose serves as an indicator and has a GI of 100 (high). The GI indicates the highest level of sugar in the blood that is reached within two hours after consuming the respective food1. The higher this blood sugar rise, the more insulin is secreted, because this hormone ensures that our cells open the barrier for the excess sugar so that it can be stored in the form of glycogen. Read more about this topic in the article about Blood sugar!

 

Digression Carbohydrates

In order to understand the relationship between sugar, glycaemic index and glycaemic load, we will first briefly clarify the basics of carbohydrates:
Carbohydrate is basically the umbrella term for various forms of sugar and, along with protein and fat, is one of the three macronutrients that provides our bodies with energy. From a chemical point of view, they are divided into three forms: Monosaccharides, Disaccharides and Polysaccharides. Multiple sugars (complex carbohydrates) are simply many sugars chained together, they are also known as starches. Potatoes, pasta, rice or vegetables contain these polysaccharides. Single and double sugars are found in fruits, honey, table sugar, syrup, confectionery and in many processed foods.

For the topic of blood sugar, it is only important at this point that our intestines only ever absorb single sugars, whereby double and multiple sugars must first be broken down by digestion. We then absorb simple sugars via the intestinal mucosa in the form of glucose (dextrose) and fructose (fruit sugar). Fructose can be converted directly into energy, but is often also very quickly converted into glucose by the liver and released into the bloodstream or converted into fatty acids and stored. Glucose is the sugar that stimulates the storage hormone insulin. It gives our cells the signal to open the cell for the glucose when the blood sugar level rises. The glucose is then stored in the cell as glycogen. When these limited stores in muscle and liver cells are full, the remaining sugar is converted into fatty acids by the liver and stored as body fat in the almost unlimited fat stores.

With this background information, the bridge can now be built to the glycaemic index: The more carbohydrates are eaten and the faster the simple sugars arrive in the bloodstream, the higher their glycaemic index. The problem is, however, that the index does not take into account how high the carbohydrate content is in the respective food, which makes the glycaemic load much more important.

 

Glycaemic load - what is it?

Glycaemic load (GL) refers to the carbohydrate effect based on the glycaemic index and portion size. The value is based on the respective number of the GI and the density of carbohydrates contained in the respective food1. This all sounds very abstract and complex, which makes the following practical example helpful:
For example, cooked carrots and wheat bread both have a glycaemic index of 70, which is already a high value and could give the impression that both foods greatly increase blood sugar levels. However, in 100g of cooked carrots there are only about 7g of carbohydrates, while in 100g of wheat bread there are 49g of KH. Thus, in the end, the bread has a seven times higher glycaemic load and causes a much higher increase in blood sugar than the 100g of carrots. Thus, the glycaemic load should be considered more than the glycaemic index. The so-called Glyx diet, which is only oriented towards the former, is therefore often flawed.

Here is another mathematical illustration of the example:

 

Food

Glycaemic index

KH per 100g

[KH (net) per 100 (GI)] / 100

Result = Glycaemic load

Wheat bread

70

49g

(49 × 70) / 100

= 34.3

Bought carrot

70

7g

(7 × 70) / 100

= 4.9

 

So you can see that the value for carrot decreases from 70 to 4.9 and for wheat from 70 to 34.3. A glycaemic load of 0 to 10 is considered low, 11-20 moderate and anything above 21 is considered high. Accordingly, while carrots have a high glycaemic index (70 and above is high, 56-70 is considered moderate and below 55 is low), they have a very low glycaemic load. This is in complete contrast to wheat flour2.

Thus, 100g of wheat flour causes a sharp rise in blood sugar, but 100g of cooked carrots do not.

 

Glycaemic load and glycaemic index do not take portion size into account

However, one indicator is also missing in both systems, the glycaemic index and the glycaemic load: the amount of the respective food that is consumed and the sum of several of these foods. The sweet potato, for example, has a GI value of 50, which means it is still in the green zone in terms of the index, but already reaches the moderate level in terms of the GL value with 12.1.

If you now take into account that you eat 150-200g of sweet potato in one meal to get full, you reach a net GL value of 24.4. This already counts as a high blood sugar level, which is why a mountain of sweet potatoes can strongly stimulate insulin secretion. This example is in no way intended to show that the sweet potato is a bad food, but only to illustrate the complexity of the issue. With other foods it is exactly the opposite, a regular portion of blueberries of 60g, for example, has a net GL value of 0.9, which means that this portion does not lead to a high blood sugar level despite the minimal sugar it contains.

 

Conclusion on the glycaemic index / glycaemic load

Awareness of glycaemic load and glycaemic index is good basic knowledge on the subject of blood glucose levels and their stabilization. However, they should be used as background knowledge and not as isolated values. The amount of food, but also the time at which one takes it, the current physical condition, intestinal health as well as genetic factors play an additional role. A muscular athlete with a low body fat percentage can easily fill his glycogen stores with a mountain of sweet potatoes or porridge with maple syrup on a training day - someone who is overweight and also does little exercise should, if possible, consume meals with an overall low glycaemic load. And even foods that are low in all three of these values can trigger problems in the body. A good example of this is synthetic sweeteners such as aspartame.

 


References:
1 Strom, Daniela (2013): Glykämischer Index und glykämische Last – ein für die Ernährungspraxis des Gesunden relevantes Konzept? - Wissenschaftliche Stellungnahme der DGE. In: Ernährungs Umschau. Bonn: DGE.
2 Fachgesellschaft für Ernährungstherapie und Prävention (2021): Recherche-Tabellentool Glykämischer Index und Glykämische Last von Nahrungsmitteln. [https://fet-ev.eu/glykaemischer-index-ballaststoff-index/2/; 25.04.2021].

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