more on protein 'toxicity'.  notice that the normal ureagenic [ie production
of safe urea unsafe from ammonia] is 'so great compared with physiological
load' in health.  perhaps a shortage of fats impairs this mechanism, or
perhaps the whole issue of bogus...

The biologic requirement for tight regulation is satisfied, because the
capacity of the hepatic urea cycle exceeds the normal rates of ammonia
generation in the periphery and transfer into the blood. Hyperammonemia
never results from endogenous production in a state of health.  An elevated
blood ammonia level, although it may be secondary, must never be ignored.
Moreover, since the normal ureagenic capacity of the liver is so great in
relation to physiologic load, such a finding points directly to an
impairment of the urea cycle
http://www.emedicine.com/ped/byname/hyperammonemia.htm

andrew