Dios mio..this again! You should eat that 100g of protein then pee in their mouths... it will be partially digested and they'll absorb it faster!
Its not true. In fact, if there is significant protein in the urine this is a marker of kidney issues.
First, proteins are made up of amino acids. WHen you eat protein it is broken down into aminos and absorbed into the blood.
There are 20 amino acids that the body uses for various purposes: tissues, hormones, enzymes, transporters, etc.
Next, there exists in the body a free amino acid pool. This pool is made up of blood and tissue amino acids in equillibrium.
The body maintains this amino acid pool in various ways. If protein intake is high, it will convert amino acids in the liver into glucose or fatty acid derivitives (put simply). When amino acid levels are low the body will either convert derivitives into amino acids, or catabolize tissues to release amino acids.
Protein metabolism is a complex system, but in no way do you piss or poop out the protein eat. And there is no magical 20 gram or 40 gram number.
Br