True. It's called Pica. People from third world countres will even chew on such inert material such as dirt (soil).
I have been there, cracking my teeth and seeing my hgb go down to 5.7. As I write, it just went from 14 to 11.6 and guess what I am chewing?
11.6 doesn't yet demand Iron infusions ( can't take oral) and vitamin B12 shots, but I'm on my way.