Terry Morse wrote:

In article ,
Peter wrote:


Terry Morse wrote:


"Just as important, though, is the fact that simple sugars, unlike
complex carbohydrates, take longer and require more fluid to empty
from the stomach and GI tract."

This statement totally ignores the fact that complex carbohydrates can't
be absorbed from the stomach and GI tract at all - they first have to be
broken down into monosaccharides...


I don't think this invalidates their comment, but it certainly casts
a shadow over the fuild transport situation. They claim that complex
carbs will be absorbed at the same 6-8% concentration as simple
sugars, but since the carbs have more energy content, they carry
with them more fuel. What they don't mention is that the carbs are
broken down into simple sugars in the intestine, raising the
concentration, which reportedly shuts down the stomach emptying.

Of course they don't mention that since it destroys their whole
argument. Complex carbohydrates aren't absorbed at any concentration so
the way you get the fastest absorption is to start with monosaccharides
that don't have to be broken down first. Adding additional steps won't
speed up the process.


"This is due to a physiological
feature known as osmolality...If the osmolality of your sports drink
deviates from body fluid levels, it will not absorb. A simple sugar
drink will only match regular body fluid osmolality at a very weak
6-8% concentration; otherwise, it will remain in the stomach until
sufficiently diluted.

Anyone who has mildly 'bonked' and then been rather quickly revitalized
by drinking a coke or other sugar-rich drink will recognize that the
sugar didn't just sit in the stomach waiting for them to drink lots of
additional water to achieve this dilution.


Well, that concentrated sugar solution had to get through the
intestinal wall some how, and it can't climb an osmolality gradient
to do it. I don't think there are any pumps in the intenstines for
moving fluids.

As quoted befo
http://arbl.cvmbs.colostate.edu/hboo...b_sugars.html:
"Particularly important dietary carbohydrates include starch and
disaccharides such as lactose and sucrose. None of these molecules can
be absorbed for the simple reason that they cannot cross cell membranes
unaided and, unlike the situation for monosaccharides, there are no
transporters to carry them across."
Those transporters do act as a form of pump for getting the
monosaccharides (molecules - not fluids) into the bloodstream. But in
any event, the gradient in this case is in the right direction - you
have a higher sugar concentration in the intestines so there will be a
natural tendency to get it into the bloodstream where the concentration
is lower.

From what I understand, when you have a concentrated
solution, fluid will flow from the bloodstream into the intestines
until the solution is isotonic (same concentration as the body's).
When hydration is at a premium, that's probably not a great idea.

That's the standard osmotic pressure with a semipermeable membrance that
permits water to pass but blocks the dissolved substance. But in this
case the monosaccharides are able to pass through the intestinal wall
membrance. So the concentration can equalize just by moving the sugar
molecules into the bloodstream.