On Sun, 17 Sep 2000 04:48:14 EDT, Denise LePage <[log in to unmask]>
wrote:

>It is my understanding, from Lyle's book, that neoglucogenesis only occurs
>when the body does not have sufficient glucose.  I could be wrong, and I
>suppose he could be.  But converting 58% of *all* protein into glucose
>seens
>very strange and doesn't ring with what I read (with the book out on loan
>so I can't verify).

Gluconeogenesis means rebuilding of amino acids to glucose as fuel.
While unsage of amino acids for structural purposes has priority in
the
body. But in times of starvation or in a low-carb diet, the body is
devoid
of carbohydrates, which are an essential food for some tissues and
starts to
downgrade more amino acids, even in cannibalizing proteins from muscle
cells.

The body has no means of discarding amino acids once eaten. It can
only
discard excess nitrogen (the excess part when building glucose of
amino
acids) in form of urea (and ammonia, i think). At least i haven't
heard
about amino acids in the urine.
It has little storage capacity for proteins.

All food proteins have an unideal composition of amino acids, which
doesn't
match the actual need (for structural purposes). So unneeded amino
acids
show up - which need to be discarded. They are burnt for calories.
58% unusable amino acids are a realistic percentage for a diet with
moderate
protein intake of good quality (like meat).

Well most of you know these facts, but given these puzzle stones i
think
makes up an explanation of your numbers. I try:
1.Every protein, which is not used structurally (or as agent) is
rebuilt to
glucose. This will be about 50% even for good quality protein as meat.
This rate will go up much higher (90% or more) in high protein diets.
2.In absence of dietary glucose, minimum the essential amount of
glucose is
derived from protein, may it be in the food or not.

Todd wrote:
>If the 58% conversion rate is accurate, regardless of
> glucose intake, then this would perhaps be evidence that for a
> very long time glucose intake was seldom adequate, so that it
> made sense to convert protein at this constant rate.

Given constant 58% conversion was accurate, where would the excess
amino
acids go to then? Obviously they don't end in additional muscles. ;-)

After frugivore time, the paleo foodstuff seems to have been rather
low in
calories (But i think seldom devoid of carbohydrates).
In this way the protein intake was relative high (when thinking of
both, plants or animals).

Therefore the gluconeogenesis engine was required and used at all
times.
As we know from Loren Cordaine there's an upper limit of what it can
deliver: 35% of all calories, called the limit of protein toxicity.
Actual this won't be protein becomeing toxic, but the toxic
gluconeogenesis
byproducts,particularly urea and ammonia. Possibly also the body
acidity
(pH) and its inability to metabolize nuclein-acids (=purins).

Cheers

Amadeus S.