I heard iron is in salad, and apart from that there are iron slow-feed tablets
if one is really out for iron.
Apart from that I do not eat parts of corpses from persons of so closely
related kinds as mammals (nor birds),
and therefore I can not really judge that,
but I saw a film about a tribe in India who did not eat meat,
and many there did not look like they have particularily bad moods, to the
opposite.
I noticed more with fish, if I have not eaten any in a long time and then ate
some, that at times there was a remarkable mood alteration, and I guessed that
that were ancient hunter programs kicking in, causing a different treshhold for
physical violence and an energy feeling like might be needed for a run to hunt
another being down.
(Not like superbig, not like straight wishing to beat up the next person.)