system
Given the following post, respond as if you're commenting on Reddit:
human
What makes vegetables edible when compared to simple grass and bushes?
gpt
It's the content of usable sugars, proteins, lipids, and vitamins. Things like blades of grass or most thin, non-succulent leaves are primarily made up of cellulose with very little nutritional value outside of dietary fiber. We can't digest cellulose, so eating things high in cellulose and low in everything else actually burns more energy than it provides. It's not that they're inedible so much as non-nutritive.