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?
I’d accept the structures within what we define as food being a social construct. Status as fruit or vegetable doesn’t qualify it is healthy as we tend to assume. A potato is a plant and it has more in common with a loaf of bread, a yellow banana has less good in it than a Snickers bar.
Food in total though, that’s a defined thing. Glass isn’t food because we’ve agreed as a society not to eat it, it’s not food because we can’t process it in any meaningful way.