Essential amino acid requirements

pathos pathos at
Fri Dec 17 08:42:26 EST 1999

In article <38592328.423B at>, Stuart Dunn <dunns99 at> wrote:

> pathos wrote:
> > 
> > In article <3858BEBC.1EDD at>, Stuart Dunn <dunns99 at> wrote:
> > 
> > > > 2) Calcium levels have nothing to do with pH of the urine.
> > 
> > > They do effect the pH level of urine. The breakdown of protein produces
> > > acids which are then excreted through the urine. Since the pH level of
> > > urine must be maintained, the body excretes more calcium in the urine.
> > > Cysteine and Methionine are the amino acids that increase calcium loss
> > > when consumed to excess, and most people get lots of these two amino
> > > acids from nonvegan foods. I did find some interesting information on
> > > protein, and I'll post it sometime today.
> > 
> >    1)Proteins are not broken down in the kidney.
> You think I didn't know that? I am not refering to protein digestion. I
> was refering to the fact that amino acid breakdown produces urea and
> other acids that are excreted through the urine.

 Stuart Dunn said:
"Cysteine and Methionine are the amino acids that increase calcium loss
when consumed to excess, and most people get lots of these two amino
acids from nonvegan foods." 

I assume when you say that Cys and Met increase calcium loss that the loss
of both calcium and those two amino acids occured together through the
kidney.  I reckon that I simply misunderstood you.

Another little sticking point is that Urea is not an acid.  If anything,
it is more of a detergant-like substance.  Most excellent at denaturing
proteins.  It does not alter pH in any way, Uric acid on the other hand

After doing some reading which I had little time for but was a good review
of classes long gone, I found the following:

There are 21 amino acids and one pseudo amino acid.  Half of these are
cosidered to be essential amino acids. They are Threonine,methionine,
valine, leucine, isoleucine, phenylalanine, tyrosine, tryptophan, lysine
and for infants, histadine.  They are cosidered "essential" because thier
carbon skeletons can not be converted.  The corresponding alpha ketoacids
can not be synthesized in humans.  So whether or not these amino acids
come from plants or meat is of little consequence, BUT YOU MUST GET THEM.
As for the daily intake of protein, the average adult has about 10 kg of
protein in the body. 6 kg is in a metabolically active pool. Approximately
50 g of protein is broken down and released by the muscle.  If you are a
big strapping body builder or a crazy rugby player or even a very active
person then this number will increase.  But for lazy geeks such as myself,
this number is pretty close.  Therefore, you only need to eat enough
protein to make up for the loss, 50g/day or 0.8g/kg of person.  When
accretion of body mass is occuring,ie growing children, pregnant women,
peaple just off diets, active atheletes or very active peaple, then the
requirement for protein may increase to 1.5-2.0 g/kg.

To all,
This is my last post on this thread.  I feel certain that Stuart has no
intention of learning basic biochemistry and physiology which is a shame
because he does have the desire to know about it.  I hope others have
enjoyed my ranting and to those that I have offended, I offer my humble

Peter Pediaditakis
University of Pittsburgh
Department of Pathology

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