I've been reading lately that one of the problems with a low fat or
vegan
diet is depression caused by a lack of omega 3 & 6 oils.  A vegan
isn't
going to be eating fish, the usual source of omegas.  Flax & hemp seed
oils
are suggested for vegans, but they seem like pretty unnatural sources
to me.
http://www.chathamhealth.com/accord/hemhemoil10m.html

Flax sprouts might also be worth investigating as a live, unprocessed
food
for the vegan.