Digestion of keratine

[The_simpsons]

Something that crossed my mind recently, can humans digest keratine-proteins (i.e hair and nails) like with other proteins, when they are broken down to individual amino acids?

[Psycho]

Well I know they can't digest keratin in hair as I remember a news story where a girl died and they found that a ball (about the size of a small american football) of hair in her stomach.