On Tue, 25 Jul 2000, Amadeus Schmidt wrote:

> 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.

A trained person adds much more than red cells.  He or she adds
muscle, in significant amounts, and that muscle needs a
continuous blood supply.  I can't give you exact figures here,
but it is well known, for example, that size makes a difference
in how much alcohol one can handle, and this is a function of
blood volume.

> This defines not the protein "need" we used to diccuss about, but only
> the temporary storage capacity of the blood.

But muscle mass directly affects storage capacity *and* need.
Muscle is metabolically active tissue, and the more it is used
the more protein it needs, for maintenance.

> 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.

LBM tissues *must* consume more amino acids than bones.

In my view there are a number of independent lines of evidence
suggesting that for human beings a protein intake of about 30-35%
of calories is optimal.  First there are the anthropological data
from the study of contemporary hunter-gatherers.  Second there is
the fact, established by Wolfe et al., that higher (i.e., higher
than the 12-15% that is typical in the developed world) protein
intake results in improved blood lipids.  Third, the importance
of arginine-derived nitric oxide seems to point to a need for
rather large amounts of dietary arginine, and this requires a
large amount of protein.

Protein-requirement studies remain equivocal precisely because
the apparent elasticity in our ability to adjust to varying
levels of protein intake.  We can survive on fairly low levels,
but to me the evidence suggests that we flourish with higher
levels.

> Derivating more than the essential carbohydrate from protein
> seems to cause some problems (this is rabbit starvation).

I need to know a lot more about rabbit starvation before basing
any strong conclusions on it.  Philip Thrift's diet appears to be
quite low in fat, and yet he has no symptoms.  On the other hand,
at the outset of the 1928 Bellevue experiment, Stefansson and
Andersen supposedly got sick *immediately* from lack of fat.
Something is wrong with this picture.

> 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.

This assumes perfect utilization of the amino acids.  Also, the
body builder's increased need for protein will also be a result
of increased maintenance needs for the tissue that is already
there.

Vegetarian body builders (or strength athletes of any sort) are
rare, and the few who exist use protein powder supplements of one
sort or another, even though (as you have often pointed out) it
is not difficult to get RDA levels of protein from vegetables.

Todd Moody
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