[King Grub]

The rate of amino acid absorption from protein is quite slow (~ 5 to 8 g/h, from Table 2) when compared to that of other macronutrients, with fatty acids at
~ 0.175 g ∙ kg-1∙ h-1(~ 14 g/h) (55) and glucose 60 to 100 g/h (0.8 to 1.2 g carbohydrate ∙ kg-1∙ h-1) for an 80 kg individual (56). From our earlier calculations
elucidating the maximal amounts of protein intake from MRUS, an 80 kg subject could theoretically tolerate up to 301 to 365 g of protein per day, but this would
require an absorption rate of 12.5 to 15 g/h, an unlikely level

Amino acid catabolism must occur in a way that does not elevate blood ammonia (26). Catabolism of amino acids occurs in the liver, which contains the urea cycle
(26), however the rate of conversion of amino acid derived ammonia to urea is limited. Rudman et al. (27) found that the maximal rate of urea excretion (MRUE)
in healthy individuals was 55 mg urea N ∙ h-1∙ kg-0.75, which is reached at an intake level of 0.53 g protein N/kg-0.75 At higher protein intakes there is no further increase
in urea excretion rate, but a prolongation of the duration of MRUE, often in excess of 24 h (27).

In a further investigation of the fate of protein nitrogen, Rudman et al. (27) were able to quantify the temporary accumulation of urea in body water during
MRUE and the amount hydrolyzed in the gastrointestinal tract. Subsequently an algorithm was developed to estimate the capacity of the liver to deaminate amino
acids and produce urea, termed the maximal rate of urea synthesis (MRUS). In a study on 10 healthy subjects, the MRUS averaged 65 mg urea N ∙ h-1∙ kg-0.75 (with
a range of 55 to 76). Thus the level of dietary protein that can be deaminated and processed through to urea by the liver in a 24-h period is dependent on body weight
and individual variation in efficiency of the process, as indicated in Table 1. An 80 kg individual, for instance, could deaminate up to 301 g protein per day, but
may be limited to 221 g protein per day, given the range in MRUS determined by Rudman et al. (27). However, the safe intake level of protein consumption may
even be slightly higher than these figures, as not all protein is deaminated and converted to urea.

http://home.exetel.com.au/surreality...n%20Humans.pdf