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What is the difference between glycaemic index (GI) and glycaemic load (GL)?

GI is a scale of how quickly foods break down and impacts blood sugar levels.  High GI means they break down and are absorbed more quickly, meaning high GI increases blood sugar more quickly.

GL is calculated by assessment of the GI COMBINED with the REALISTIC amount per serve.

What you need to remember is that in general, you don’t eat a particular food on its own – you usually eat a small amount of a mixed range of foods in a meal and will also be impacted by what else you have eaten in the day.  Taking into account fibre, protein and fat content of whole foods is very important when deciding what is good for you.

Ok, so now you are confused?  Let’s look at a couple of examples (approximated, due to portion size differences).

Glycaemic load levels:                  low=less than 10,      medium=11-19,            high=20+.
Daily total GL should be under 100

Banana has a GI of approximately 48 (low GI is classed under 55), the GL on that is 12 (medium GL).  As a snack, a banana can be quite satiating and has a good amount of fibre for size.

Sweet potato has a GI of 61 (so medium GI), but the GL is 17 – again, will contribute to a feeling of satiety – and has a good amount of fibre.

Watermelon has a GI of 103 (very high GI), but a GL of only 4 (low GL) – so it is sweet yes, but you are unlikely to sit down with a whole watermelon and still feel hungry – little fibre, but high water content.

A popular fizzy lemonade drink has a GI of 77, but the GL is only 15.  Now this is based on ONLY 250ml – not a 375ml can or a 600ml bottle.   But after having this, you will still have room for food so will eat as well as having that drink (as it is not satiating but pushes up blood sugar), then add the food, which further increases your daily GL total.

Now – DIET fizzy drinks.  No, not better for you, though generally low GI.  One of the “tricks” of these beverages is that the body thinks it is getting a sweet drink, so it prepares itself to start dealing with incoming sugar.  This encourages the body to work on dealing with that sugar (that wasn’t actually there) – so insulin is released, the body starts working on storing the incoming sugar (the liver and fat cells) – AND because there is nothing to actually deal with, you feel hungry – so you eat.

What you need to aim for, is maintaining an intake of 50-80 GL points per day, for good blood sugar control.  This is even more important if you are carrying a little extra padding that you want to lose, or you have fatty liver or type 2 diabetes (or pre-diabetes).

Here is a reference list done by Harvard Health, which will give you a little more information.

https://www.health.harvard.edu/diseases-and-conditions/glycemic-index-and-glycemic-load-for-100-foods

If you want a LOT more information, this table covers nearly 2000 foods:

http://care.diabetesjournals.org/content/diacare/suppl/2008/09/18/dc08-1239.DC1/TableA1_1.pdf

But if you want to err on the side of caution, go with fruits such as berries, apples, cherries, pears, strawberries, avocado (yes, it is a fruit), bananas, kiwifruit and oranges.

There are NO whole fruits which have a high glycaemic load.

Remember these examples – bananas have a GI of 48, but a GL of 12, watermelon has a GI of 102 (high), but a GL of only 4.

 

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