Definitely gluten. I've experimented with eating it, not eating it, and now have been gluten free for over 5 years since. My brother stopped eating gluten a few years after I did, and it also had a major impact on his mental and physical wellbeing.

Not sure for gblain, but for me I actually broke out in pimples when eating excessive wheat/bread. Under a certain limit, I just felt bad.

However, I'm not sure if it's just gluten or glyphosate toxicity [1] (being concentrated in GMO wheat as that includes "roundup ready wheat" which, clearly gets more roundup on it).

[1] https://www.ncbi.nlm.nih.gov/pubmed/15862083