The Chinese cohort of our "group", upon one of them graduating, took the whole group out (Dutch of course!) to one of the local Chinese restaraunts in Waterloo, Ont. Well, one of the dishes (that these guys had to order weeks in advance) was, you guessed it, Chicken's feet, a delicacy in parts of China. So there are cultures that eat copious quantities of chickens feet. Fu told us that they waste nothing in China.
But as all Chemists/ biochemists know, only small molecules make it past the gut. All "proteinaceous" material is broken down into it's constituent amino acids by enzymes in the small intestine. Very large protein bits (medium sized amino acid chains called peptides, just cannot pass through the walls of the intestines. Maybe some short peptide chains can, but then they are sent directly to the liver via the portal vein, and chewed up enzymatically there, as well as in the blood, and if there are anything of them remaining they don't last long and cannot pass the blood brain barrier. That is why all protein containing "consumer products" [except things that are used in skin and hair products] are completely useless as far as medicines go, they are just too fragile ot get to the places inside the body without being broken apart into simple amino acids that one gets from all foodstuffs. THis is why the pharmaceutical industry has had such a devil of a time with the oral "absorption and distribution of peptide (protein) based products. If this were not true, then many diseases woulld have been cured by now. Look at the complex apparatus neccessary to put GDNF into the brain. If all growth and maintainence peptide drugs were more robust, (and in many cases, brain penetrable") we wouldn't need "reservoires, cannulae, and pumps" to deliver them to the areas where they are needed for activity to be translated.
The chickens feet were quite delicious actually . I use a folic acid supplement every day; it does enter the body and is useful because it is a small molecule. cs