Clement's Alexandrian Tradition was Vegetarian

For the sacrifices of the Law express figuratively the piety which we practise, as the turtle-dove and the pigeon offered for sins point out that the cleansing of the irrational part of the soul is acceptable to God. But if any one of the righteous does not burden his soul by the eating of flesh, he has the advantage of a rational reason, not as Pythagoras and his followers dream of the transmigration of the soul. [Stromata 7.6]