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.
I always know where my iron levels are based on how much ice I am crunching. My mom also crunches ice due to iron deficient anemia.
I stopped craving it 2 weeks after my iron infusion for the first time in years!