As someone who has eaten way too much sugary food I think my gut-brain coupling may have had enough of this. A few weeks ago I had a sugar binge one night and the cognitive effects were impossible to ignore the next day. Fortunately after 2-3 days I was back to normal but of my sample size of one, and in my condition (which is pre-diabetic) I observed a clear link.

It was a good experience as it's prompted me to get more serious about cutting back sugar, implemented as long term, achievable habit change.