Glycemic Index & Time

Bhima
Bhima Posts: 2,145
edited June 2009 in Training, fitness and health
The Glycemic Index is useful but i've never understood exactly what the numbers mean.

I know that the larger it is, the quicker the glucose gets into your bloodstream but how quick is "quick"?

For example, what's the difference between 100 & 99? 1 Minute?

Is there a way to estimate how long a food will take in minutes/hours before it's "useful", using the GI figure?

I always thought 100 (pure glucose) meant it was absorbed instantaneously, but i'm eating some dates now, for recovery, which are supposed to be 108! My original theory must be wrong because 108 would mean I am using the glucose before i've eaten the food! :lol:

Comments

  • jibberjim
    jibberjim Posts: 2,810
    Bhima wrote:
    The Glycemic Index is useful but i've never understood exactly what the numbers mean.

    What has your own research shown? i.e. what's unclear about say The Wikipedia entry where you'll see that the GI of a food tells you absolutely nothing about how quickly calories will be available since it's defined purely by the area under the curve over 2 hours.

    More importantly, what is your real question - what are you wanting to know about in relation to your cycle training? If it's purely about GI, I'd suggest a nutrition or medical science forum might be more useful to you.
    Jibbering Sports Stuff: http://jibbering.com/sports/
  • Bhima
    Bhima Posts: 2,145
    Aha... Didn't think to look on Wikipedia. That actually explains it pretty well.

    The "real question", as you put it, is to do with re-fuelling on the bike. I wanted to know how long it would take for a banana (for example) with a GI of 51 to start having an "effect", so I could know how often to eat them, although I now see it's not that simple.

    I think what i'm after are blood glucose response curves for certain foods. Could I literally just get one of those blood-glucose monitors and test myself with a banana? I believe you need 1-1.5g per kg of body mass of carbs per hour - is it best to spread your intake over the hour for higher-GI foods and shove it all in at once, every hour for lower-GI foods, to keep the curves steady?

    I used to go out and have a banana every X-number of miles but I've been going out and having a banana every 25/20/15 minutes recently to test my body's response. The tests have been quite inconclusive so i'm just trying to understand things better by looking at the G-Index.

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