I want to add to my list of benefits.  According to various sources eating
meat is supposed to make a person too restless for meditation, so if one
wishes to meditate for 'spiritual' development one should be a vegetarian.
Like many others when I took up vegetarianism it was not only for the
supposed health benefits but also to help me pursue meditation for spiritual
benefits.  However, I found that when I was a vegetarian or eating a grain
based diet I could not concentrate in meditation, was restless (constantly
checking clock) and more often than not I would fall asleep, not meditate.
I had to fight constantly to saty awake.  It was such a chore that I avoided
it.   Now eating paleo I find I am not so
restless, my concentration is much improved and I don't fall asleep when I
meditate--so I actually enjoy it.

I believe that for our hunting ancestors it was often necessary to sit very
still in "meditation" when pursuing or waiting for a chance to kill game.
Watching cats I also see that they can be very still and one-pointed in
concentration for periods of time, waiting for just the right moment to
expode from stillness into action and grab the prey.  If meat-eating made
them too antsy to sit so still I suppose they (the cats and our ancestors)
would have died out long ago.

Don