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Glycaemic index versus glycaemic load

A question I often come across is what the difference between GI and GL is. Let’s see if we can clear this up for you once and for all because it’s quite an important issue when it comes to our diet. Definitely more than counting calories.

The glycaemic index is a measure of how quickly and how high our blood sugar rises after we eat. I’m sure you’ve seen tables or list indicating the GI in different food stuff.

However GI is not nearly as important as a less famous measure called the glycaemic load (GL). So let’s see what we mean by GL.

When we eat any food- especially carbohydrate and to some extent protein- our blood sugar goes up. (It hardly goes up at all when we eat fat though). In response to the rise in blood sugar, our pancreas secretes insulin, whose job is to act as a traffic warden and escort the excess sugar out of the bloodstream and into the cells where, ideally, it can be used as fuel. What follows is that blood sugar and insulin bit by bit go back down to pre-eating levels, and in a few hours we repeat the whole process.

The only issue is, this is anything but an ideal world.

We overeat high sugar carbohydrates, which quickly drives our blood sugar up through the roof. The pancreas sends out a torpedo of insulin in an attempt to lower blood sugar, but most of us are pretty sedentary, so our muscle cells aren’t interested in accepting it. Insulin knocks on the doors of the muscle cell walls and the cells say, “Sorry mate, we don’t need any sugar, our guy’s going to be sitting in front of the tele all day, go climb a tree”. (Sugar ends up going to the fat cells, which are far more welcoming.) Meanwhile both blood sugar and insulin have been raised, setting us up for hypertension, fat storage, hunger, cravings and mood crashes when the sugar ultimately does drop.

Nothing to write home about!

To measure the effect of food on blood sugar, scientists came up with the idea of the glycaemic index. Using pure glucose as a standard (with an index of 100), they tested 50 gram portions of digestible carbohydrate and measured how quickly and how high blood sugar rose in reaction to eating them. By eating low-glycaemic index foods we presumably could avoid the blood sugar roller coaster.