Ben,

I am interested in your proposed concept regarding organ meats and the
dietary protein ceiling.  It is my understanding that urea formation is the
limiting physiological factor (as you had mentioned earlier).  If urea
formation was at its maximum, additional protein channeling into catabolic
pathways would theoretically yield an increase in ammonia production
(neurotoxic).  It is also my understanding that the only way to curtail
urea formation, at least in a physiological sense, is to curtail net
protein catabolism.  This would require a close match between dietary
protein intake and anabolism/maintenance of tissue proteins (protein
deposition into tissues, such as muscle
mass, or even as an
increase/maintenance of metabolic enzymes).

If, however, organ meats were substituted for "muscle meats", how might
this "ceiling" be raised?  Are you proposing that there might be a
mechanism for:

-increased hepatic capacity for urea formation?

-decreased ammonia toxicity (due to body compartment channeling or improved
ammonia metabolism/excretion)?

-increased anabolism (increased protein accretion at the tissue/enzyme
level)?

These 3 mechanisms seem to be the only ones that are plausible. However, I
would not presume to preclude the fact that you may indeed have a fourth
mechanism in mind.  The arguments that I've seen in journal articles imply
that fat intake must be high enough to limit protein intake to about 35-40%
or less of total energy intake (or suffer the metabolic consequences of an
ammonia burden).  They have n
ot forwarded a specific argument (beyond
increasing the contribution of fat to the protein in found in meats) for
organ meats.  Would you please elaborate on a mechanism for an "organ meat-
induced" increase in dietary protein tolerance?

Ed Thompson