Translation:I don't eat meat.
"I eat a vegan diet" (no animal products): "我吃素” (wǒchīsù)
"I eat a vegetarian diet" (eggs and milk are OK): "我吃蛋奶素" (wǒchīdànnǎisù)
> Though in Chinese, "素" tends to connote Buddhist vegetarian ("素" literally means plain / elemental), wherein garlic and onions are grouped together with meat as being off-limits.
> In Taiwan if you want to communicate that you are OK with garlic and onions, you could say "我吃健康素" (wǒchījiànkāngsù), which is literally "I eat healthy vegetarian" i.e. I eat it for heath reasons, not religious (and hence the religious restrictions on garlic and onions doesn't apply to you).