I was imbued with this [vegetarian] teaching, and began to abstain from animal food; at the end of a year the habit was as pleasant as it was easy. I was beginning to feel that my mind was more active.
– Seneca to Lucilius, CVIII. On the Approaches to Philosophy, 22
This is an interesting passage from Seneca, and while the Stoics dont necessarily advocate for veganism, we do have to wonder if they would be if they were alive in these modern times.