They are healed by radiation. The food however...dunno
I do believe that ghouls depend on food and such. One example is when you do the Come Fly With me quest and meet the ghoul in the cellar that set up several traps. When talking with him (if you do not choose) to kill him, he will mention that he still have to eat, and when going up on his ledge, you will see a fried mantis, which implies that he do indeed have to eat.
Another example is that you sometimes find strange meat on the feral ghouls