It is the million dollar question: just how does installation of a GFCF diet affect behaviour and other functions in relation to cases of autism? Sadly, we’re going to answer this question quickly before we go off exploring potential modes of action, by saying nobody really knows how diet might affect the presentation of autism. There’s plenty of speculation and fitting together of pieces of often quite disparate pieces of evidence but that’s about it. Readers are also well advised to tread carefully when coming across anyone who says that they know how dietary intervention might be working in autism.