BoED had a Vow that required the character to "not touch dead flesh" of any kind - assuming that the flesh has to be that of a creature, and "fruit flesh" doesn't count - that would be a Vow that basically requires strict vegetarianism.
You are correct. Vows like that exist in real life and their adherents limit their diet to fruits and plants.
"It's the fate of all things under the sky,
to grow old and wither and die."