Mixing Food with different GI

GI (Glycemic index) has always seemed to me an inexact measurement.

Eg Wikipedia states that, for a given food, the GI can vary due to ripeness, cooking methods & processing ([https://en.wikipedia.org/wiki/Glycemic_index]

A further variation is introduced when mixing food together eg the GI of a baked potato is relatively high but add in some fat (butter / cheese) & the GI reduces.

When treating a low BG, I normally like to eat something with a high GI (eg glucose tablet with GI = 100) to get my BG back into the normal range. Then, if I’m exercising, I like to eat something with lower GI (eg banana, biscuit, chocolate etc) to keep my BG in range over a period of time.

My question is if I eat glucose tablets followed by a lower GI food, will they mix together (like baked potato & butter) & slow down the quick absorption of the glucose? Can I eat one direct after the other without affect or do I have to leave a certain amount of time in between to allow the glucose a head start !


My guess is that high fat foods could slow down the absorption of the glucose, but low GI foods in general not necessarily. Potatoes, for example, have a lower GI than glucose because the body needs to convert the starches into glucose first, but I don’t think starches slow down glucose absorption.

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Sounds like a great topic to run a personal experiment on and share with everyone!

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No scientific proof, but if I was on the low side, I would wait 5-10 minutes after glucose before eating potatoes or other carbs.
BTW, I have heard that once cooled, cooked potatoes turn to resistant starch which raise BG much slower, lower GI.


I would do the same :slight_smile:

It’s known that cooked & then cooled pasta has similar properties ie much lower GI than the original cooked pasta. Re-heating it again doesn’t raise the GI.

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Definitely. If I go low in the middle of a meal – usually because the prebolus was way too early – then if I eat glucose tabs mid-meal they never raise me as much, or as quickly, as they do when eaten on their own. That’s scientific enough for me.


In my humble opinion, GI is a very useful concept, but flaky science.

First of all, GI is calculated based on very small samples of non-diabetic volunteers. A big factor of the GI is how a healthy pancreas responds to particular foods. (As you may be aware, a healthy pancreas starts secreting insulin merely by the scent food; and it will respond differently based on the flavour, volume, and consistency of food.)

Second, as soon as the “Low GI” marketing symbol was created, well, you know what money does to science.

As I said, it’s a good concept. But above all use your personal experience and your brain.

Coming to your question, pretend you are taking some foods and crushing them over a bowl of vinegar (to represent stomach acid). If you have cooked cheese and potatoes, they will remain clumped together and take time to break down. OTOH if you drop in a crushed sugar tablet and a crushed biscuit, the sugar tablet will simply dissolve and will not mix with the biscuit. Once something is dissolved in stomach acid it readily moves across the stomach lining into the bloodstream.

(Contrast this with chocolate, where the sugar is dissolved in the fat. The sugar filters into the acid very slowly. Don’t treat lows with chocolate.)

I’m not a doctor and this is all conjecture, but based on my experience, eating a biscuit or banana will not significantly slow down the effect of glucose tabs or juice/cola on your sugar. Things can be different if you eat more than that; since the mixture becomes more viscous and the dissolved sugar has a harder time making its way to the stomach lining.


I agree with your opinion - GI is a useful concept but as it’s flaky science, quite difficult to use in a practical way. I’ve often seen different GI values quoted for the same food & consequently categorise food into high, medium or low GI rather than exact values

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The principal route of glucose absorption is the upper portion of the small intestine. I’m not aware of evidence that the glucose readily moves across the stomach lining into the bloodstream.


There’s mixed evidence about whether glucose has significant absorption through the mouth tissue. On the one hand, some say no:


On the other hand, there are studies that show that sugar held under the tongue is effective.


Oh, thanks for that. Always more to learn about this stupid thing. Time to revise mental model…