Glycaemic index vs glycaemic load

Today I’ve been doing some reading about glycaemic index (GI) and glycaemic load (GL), and I thought it would be nice to share my findings with you all. When you are first catapulted into the world of diabetes, the term GI is mentioned a lot, and my aim was to better understand what GI actually is, and how it relates to glycaemic load of a meal/dish/cupcake…

Glycaemic index (GI) is a measure of how quickly a carbohydrate is digested and absorbed by the body, and thus how quickly it has an effect on blood sugar levels. For those who are interested in the history of the measure, it was coined in 1981 by a scientist named DJ Jenkins (if anyone wants any further info on this, please leave a message and I will be happy to direct you). GI is recorded as a score from 0-100, versus pure glucose which has a score of 100. Anything with a GI of 0-55 is considered “low”, whereas above 70 is considered “high”. However, looking at the GI score in isolation is not very informative, as, intuitively, blood sugar level is effected not only by the rate at which a consumed carbohydrate is digested/absorbed by the body, but also by the amount of that carbohydrate that you eat. What I mean by this is we know that glucose has a GI of 100, but to calculate what effect eating the glucose has on blood sugar levels is important to take into account whether you have eaten 1g, 10g or 100g of the glucose. This is where glycaemic load (GL) comes into play.

To calculate the glycaemic load of a meal, you use this formulae: GL  = GI x carbohydrate / 100. This gives you a numerical score again, but this time the parameters are shifted for what is considered low, medium and high GL; a low GL is a meal with a score of 0-10, and a high score is >20. Bearing this is mind, I’ve been calculating the GL of a few of my diabetic-adapted recipes, and have found for example that my “normal” banana chocolate cupcake recipe has a GL of 23.8, whereas my diabetes-adapted recipe has a drastically reduced GL of 9.7. What does this mean in a practical sense? Well it means that you will not get such a sharp blood sugar spike after eating the diabetic-friendly version of the cupcake; to coin a topically-relevant term being thrown around a lot at the moment it has “flattened the curve”!

For anyone who is interested in further reading around the topic, I found that the diabetes.org.uk webpage on the topic is a good place to start and includes some useful example illustrative scenarios https://www.diabetes.co.uk/diet/glycemic-load.html. And because I am a scientist by training, for those more scientifically minded there is a huge wealth of literature available on the topic, but I found table 2 within this publication particularly enlightening in terms of illustration: (N.Mcclenaghan 2006, Nutrition Research Reviews, Determining the relationship between dietary carbohydrate intake and insulin resistance).

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