Glycemic load : I don't get it

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In summary, the glycemic index was created to allow for comparisons of different foods. It does not take into account how much carbohydrate is ingested, so the glycemic load was created to better reflect the amount of carbohydrate in a given food.
  • #1
Aymeric
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Hello,

From what I have read, the glycemic index is a limited tool because it doesn't take the amount of ingested carbs into account, hence why the glycemic load was created.

But then I read an example that threw me: a serving of 10g with an GI of 100 is equivalent to a serving of 100 g with a GI of 10, since they have the same GL of 10.

So my question is: how do we know that blood glucose levels will rise constantly? Is glucose absorption really constant and unlimited? I don't think it is the case with other nutrients, is it?
I mean, what if they rise constantly with the first 90g of GI=10 food, and then the rise slows down with the final 10 grams (because of some kind of saturation for example, although I haven't studied glucose metabolism yet), which would cancel the equivalence suggested by GL calculation? Or the other way round? What if it increases 'normally' at first, and then more and more as the intake gets bigger?
Is it an established fact that blood glucose increase is directly proportional to quantity x GI ?

I hope my question is clear...

Thanks!
 
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  • #2
Simple answer - Type I diabetics do not make insulin. They were fed a carefully measured amount of some food and the rise in blood sugar was measured.

That is simplified model for glycemic index calculation. Pure glucose was assigned a de facto 100 value as a standard. If administration of whole wheat bread caused a rise of 80% of glucose it got a number: GI 80.

Multiply the glycemic index by the amount of carbohydrate in grams provided by a food and then divide the total by 100. This is glycemic load

Glycemic load was developed by scientists to simultaneously describe the quality (via glycemic index) and the quantity of carbohydrate in a meal or diet.

http://lpi.oregonstate.edu/infocenter/foods/grains/gigl.html#gl

In other words glycemic load is meant to be used for real food - a mixture of carbs, protein, fat, water, etc.
 
  • #3
Many thanks for taking the time to post!
However this doesn't answer my question, probably because I wasn't clear enough.

I know what GI and GL are and how they are calculated.

What I wanted to know is whether it has been established that glucose absorption is constant and unlimited, as opposed to other nutrients such as Ca and Fe whose absorption decreases as the amount of Ca and Fe in the intestine increases.

And I'd also like someone to confirm (or not) my understanding that constant and limitless absorption is a condition for GL to be an accurate tool (eg for the common statement that '10 g of GI 100 food = 100 g of GI 10 food' to be true).

Thanks!
 
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  • #4
Aymeric said:
What I wanted to know is whether it has been established that glucose absorption is constant and unlimited, as opposed to other nutrients such as Ca and Fe whose absorption decreases as the amount of Ca and Fe in the intestine increases.

And I'd also like someone to confirm (or not) my understanding that constant and limitless absorption is a condition for GL to be an accurate tool (eg for the common statement that '10 g of GI 100 food = 100 g of GI 10 food' to be true).

Thanks!

The short answer is no. This is a field of active research. There are at least two classes of systems that are involved in glucose transport across cell membranes including the gut. One is the sodium dependent SGLT system and the other is the non N+ dependent GLUT system. There are a variety of variables that seem to affect the activity of these systems (medications, dietary factors, gender). You can search the literature for some of these.

The GTT "normals" are based on population averages for non-diabetics and should be considered as approximate.

physrev.physiology.org/content/91/2/733.full

www.jbc.org/content/265/22/13276.full.pdf
 
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  • #5


Hello,

Thank you for your question. The glycemic load is a measure that takes into account both the glycemic index (GI) and the amount of carbohydrates in a food serving. The GI only measures how quickly a particular food increases blood glucose levels, while the glycemic load also takes into account the amount of carbohydrates in that food.

In the example you provided, it is true that a serving of 10g with a GI of 100 is equivalent to a serving of 100g with a GI of 10, since they both have a glycemic load of 10. However, this does not necessarily mean that the blood glucose levels will rise constantly in both cases. The glycemic load is just one aspect of a food's impact on blood glucose levels, and there are other factors that can affect how quickly and how much blood glucose levels will rise.

It is not an established fact that blood glucose increase is directly proportional to quantity x GI. There are many other factors at play, such as the composition of the food (e.g. fiber content, fat content) and individual differences in metabolism. Additionally, as you mentioned, there may be saturation points or other factors that can affect how blood glucose levels respond to increasing amounts of a food.

So while the glycemic load is a useful tool for understanding the overall impact of a food on blood glucose levels, it is not the only factor to consider. It is important to also consider the glycemic index, the amount of carbohydrates in a serving, and other factors when evaluating the impact of a food on blood glucose levels. I hope this helps clarify the concept of glycemic load for you.
 

What is glycemic load?

Glycemic load is a measure of the impact of a food on blood sugar levels. It takes into account both the type of carbohydrates in a food and the amount of carbohydrates in a serving.

How is glycemic load calculated?

Glycemic load is calculated by multiplying the glycemic index of a food by the amount of carbohydrates in a serving and then dividing by 100.

Why is glycemic load important?

Glycemic load is important because it provides a more accurate measure of a food's impact on blood sugar levels compared to just the glycemic index. It takes into account the amount of carbohydrates in a serving, which can greatly affect blood sugar levels.

What is considered a low, medium, and high glycemic load?

A glycemic load of 10 or less is considered low, 11-19 is considered medium, and 20 or more is considered high. It's important to note that these ranges may vary depending on an individual's specific dietary needs and health goals.

How does glycemic load affect health?

Consuming a high glycemic load diet has been linked to an increased risk of obesity, type 2 diabetes, and heart disease. Monitoring and managing glycemic load can help regulate blood sugar levels and potentially improve overall health and well-being.

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