I really like this idea and have been thinking about it also.
First, you can eat natural foods like apples, oranges, and bananas. If some of the orchards that are in the game became clickable you could gather apples/oranges/bananas and eat them.
Second, and this would be really fun for me as a rper, if you find the right books laying around in game, you can learn which plants are edible and which ones are poisonous. Once you read the book, which could take some amount of time per chapter, your character would then unlock different plants, or skills as they learned more.
Simple idea, might be hard to implement.