Hear me out. There's nothing innate to an object that makes it "food". It's an attribute we give to certain things that meet certain qualities, i.e. being digestible, nutritious, perhaps tasty or satisfying in some way, etc. We could really ingest just about anything, but we call the stuff that's edible "food". Does that make it a social construct?
Our naming and classification of things is all socially constructed. So yes, our categorization of edible things as food is a social construct, but our physical need to fuel our bodies with something digestible is not.
i love you
But also, using it that way makes existence a social construct, so it depends on how rigid you want to be.