From: sbharris@ix.netcom.com(Steven B. Harris)
Subject: Re: Blasting Steve Harris, MD (was: DEMINERALISATION symptoms)
Date: 01 Sep 1996
Newsgroups: sci.med.nutrition,misc.health.alternative

In <3229D82B.22B1@phy.ucsf.edu> David Blake <dblake@phy.ucsf.edu>
writes:

>FWIW, I think Steven Harris is one of the better voices of reason
>in this forum, but I think he is misleading on fructose
>metabolism above.
>
>Glucose is not converted to fructose before being burned. Glucose-6-P
>is converted to fructose-6-P which is then converted to fructose-1-6-P
>which is then burned - and all these steps take place inside the cell.

Technically, yes.  But you see what I meant.


>Fructose that is taken in by the body has to get processed in the liver
>first before it can be used by the cells in the body.

   Not necessarily.  Kidney and gut cells take it up as well, as well
as adipose tissue (which can phosphorylate it with hexokinase).  Yes,
the liver, with its fructokinase, seems to be the prime uptake organ,
but fructose still disappears from the blood twice as fast as glucose,
so this process is pretty efficient.


>The human body is surprisingly intolerant to fructose ingestion.
>We took hydrogen exhalation tests as a measure of malabsorption
>in GI physiology in med school. NO ONE can digest more than 50
>grams of fructose on an empty stomach. Most people can digest
>much less than that before showing malabsorption symptoms (bloating,
>gas, diarrhea). On average you are better off with lactose than
>fructose

   A rather artificial test, wouldn't you say?  Fructose in nature is
consumed with fruit-- lots of fiber, slow release.  A fair amount also
appears in sucrose, which of course is taken up by fairly efficient
disaccaridases.

>at least some people can digest lactose efficiently.

   Everybody digests fructose as efficiently as they need to.  You
don't get diarrhea from drinking orange juice.


>What's more, it has been firmly established that high fructose feedings
>CAUSE insulin resistance in humans.

Uh, uh, not in the long term, it hasn't.  On the contrary, evidence is
good that humans adapt quite well to high fructose diets.  Unlike
rodents.  All those derangment studies with fructose and humans are
SHORT term studies (hours or days).  Find one running for weeks or
months and prove me wrong.  The article I quoted has an excellent
review.


>FWIW, a link between fructose-
>induced insulin resistance and magnesium deficiency-linked insulin
>resistance has recently been found - in rodent studies.

Yes, in rodent studies.  Worthless for this topic.  If you're a rat,
you shouldn't eat fructose.  Next rat that comes to me for a health
consultation, I'll be sure and council him very well on the issue.

> If rats
>are fed a high fructose diet - they develop insulin resistance,
>just like humans. If they are given the same amount of magnesium that
>would normally accompany such a caloric load, then they do not
>develop insulin resistance. Humans that are deprived of magnesium
>with no other dietary changes develop insulin resistance - so
>it seems likely that high fructose diets require an accompanying
>magnesium load to prevent insulin resistance.
--
>Dave Blake
>dblake@phy.ucsf.edu
>http://www.keck.ucsf.edu/~dblake