Is milk a drink or a food?

I was hoping you could perhaps settle a debate that has been rife in my sixth form college for the past two weeks. This may sound trivial but many, MANY hours have been spent debating it, even leading so far as analysing dictionary definitions in order to find an answer. I was hoping that as a farmer you may be able to answer this on going arguement: IS MILK A DRINK OR A FOOD?
Clare Pleasance