Eating is optional.
If you're playing survival mode, you've got 10 hp and different food types can restore varying amounts of it.
Falling off things reduces HP, as does being attacked my monsters.
On Teh Mine there are no monsters and you regenerate pretty fast, so food isn't required unless you want to repeatedly jump off of high places in quick succession.
EDITED: 29 Jan 2011 20:01 by BOUGHTONP