On Mon, 24 Jul 2000 11:10:47 -0400, Todd Moody <[log in to unmask]>
wrote:

>On Mon, 24 Jul 2000, Amadeus Schmidt wrote:
>>The whole blood of an adult human (70kg) can hold a maximum of about 55g
>> amino acids.
>
>This, of course, is a very rough generalization involving many
>assumptions.  A more muscular person of the same weight will have
>a greater blood volume, since muscle tissue is highly
>vascularized.
> This is why it makes sense to estimate protein
>need by LBM, rather than body weight.

Of course the 55g are a generalization, based on the average blood
volume of about 7 liters blood of a human.
A trained person increases mainly the count of red blood cells,
but the blood volume? Adding one whole liter (to 8) will be really much,
i think. 1/7 added to 55g made 63g capacity then.

This defines not the protein "need" we used to diccuss about, but only
the temporary storage capacity of the blood.
The amount and temporary caracteristic of this protein storage
is important when trying food combination (striving for optimal protein
quality).

The body doesn't have a real protein storage besides blood or muscle tissue.
Glucose and fat is stored in own storage organs
but protein has only the blood with a limited capacity.
Or scelettal muscles, which need some time to build.

This speaks for a limited amount that can be processed from a single meal
(other references as Gawen wanted, i don't have).

I wrote:
>> One day will use about 0.4*70 = 28 g of the ideal amino acids for protein
>> synthesis, from 20 to... high amounts for caloric usage.

This value of .4 g net protein *synthesis* per body kg body weight
is a result from nitrogen balance tests and disputable.
Growth, injury or infection will increase that measured rate.
I agree, that adjusting protein synthesis to LBM makes sense, because
LBM-tissues may consume more amino acids than bones.
However, bones do require some protein too.

The total usage for caloric purpose ("fuel") may range from a small 30% of
the .4g (depending on protein quality) up to enormous amounts.
For example by inuits, derivating all of their carbohydrate
fuel out of meats (they get most of their energy fuel out of fat).
Derivating more than the essential carbohydrate from protein
seems to cause some problems (this is rabbit starvation).

>Again, this usage estimate must vary significantly according to
>exertion patterns.  High intensity exercise especially will
>increase the usage rate for those amino acids, but overall
>activity levels will also increase demand. ... If our 70kg person is a
>bodybuilder engaging in high-intensity weight training several
>times a week, things look different.

But what is the fate of the amino acids in the body builder?
What for does he have to build up so much own proteins?
Growth of muscle would be our favourite ;-)
1kg muscle has 200g protein. Additional 20 grams of protein for ten days
will be enough.
Or how fast can a body builder gain 2 lbs of *muscle*?
And how often repeat this?

>  And his high-intensity
>exercise pattern doubles his amino acid demand, so he needs
>something like 120g/day of protein to sustain this lifestyle.

For exercise, muscles need caloric input.
For this, i can see increased amino acid demand
(but carbohydrate fuel may work better).

Do you suggest, that such an exercising muscle constantly
looses amino acids, which are not reused?
Into what? urine, stool?

I've not heard of any nitrogen or amino acid loss, that's triggered
by exercise.

Amadeus Schmidt