That statement is nonsense. The human body is amply designed to digest meat, the rawer the better, overcooked meat can be carcinogenic. Our teeth are designed to cut and chew meat and the enzymes in our mouths, stomachs and gut are specifically for digesting animal protein. Cellulose in plants is what is indigestible to humans. You don't need to take extra protein digestive aids to digest meat, just don't overcook it.