cron-web.org

[A1CR]

[posted on behalf of MR and Dean; 2001-07-26]

A CRONie mentioned:
>
> From: Dean:
>
> > "I personally target about 15% of my calories from fruit, mostly
> > high-antioxidant, low GI berries ...
>
> According to http://www.mendosa.com/gilists.htm :
>
> "My main Glycemic Index page also makes clear that these are the only foods
> that have been scientifically tested, and beyond that I don't know the
> glycemic index of any other foods."

He isn't quite right, here -- Wolever & Brand-Miller actually have a
fee-for-service setup in which foods can be assessed for GI, & many
PROCESSED foods have been -- but it's likely this list is
nigh-exhaustive for whole foods because of lack of private $ to test them.
>
> Furthermore, this list is very conspicuously lacking strawberries,
> rasberries, and blueberries.
>
> Hence, I'm curious what source you used to determine that these berries are
> low GI?

In theory, the GI of most foods can be ballparked by the carb
composition -- ie the esimple sugars of which the carb (even if di- or
polysaccharide) is composed, w/some variations for fat, some acids &
starch structures (which considerations don't usually apply in fruits)
& soluble fiber (which does). In any case, all of these factors tend to
lower, rather than elevate, GI. So to get the MAX likely GI for fruits,
just multiply the no. grams CHO * the CHO type, & then divide by total
grams of CHO ["CHO" is carbohydrates].

Having actually sat down to do a few examples from Dean's (& my) list:

http://www.orst.edu/food-resource/sugar/com2.html

... I'm surprised many come out medium or even medium-high; precise
figures will often be lower than this for op cit reasons, & NB the high
soluble fiber content of berries. Eg. for apples, [(2.3 *100) + (7.6
*20) + (3.3 *62) + (0.1 * 105)]/ 13.3 =45, overestimating their actual,
experimentally-verified GI of 38, -- all that soluble fiber? (NB that
these tables are largely useless for veggies, e.g., because it doesn't
include polysaccharides. There's so little of these in berries that one
would expect that one can discount them, but for broccoli, e.g., it's a
whole new ballgame. Does anyone know of an exhaustive breakdown?).

So, for blueberries, eg, predicted GI = [(3.6*100) + (3.7*20)]/7.3= GI
59; blackberries, [(3.1*100] + (4.1*20) + (.4*62) + (.5*105)]/7.9= 59
again; Strawberries ~60, which is much higher than 32, but I'm not sure
where that figure came from.

Though less useful for many other foods, see:

http://www.orst.edu/food-resource/sugar/com1.html

-MR