The gut-brain connection do seem to be true on my end.

I am always careful to avoid carbohydrates when I am starting work that is concentration heavy.

I have a similar carbohydrate problem too.

If I have more than a small amount of carbs in one sitting, my mind will get hazy and I'll get really sleepy an hour or so later.

I did a blood test recently and everything was OK, so I'm really not sure what the problem is.

And funny thing is that I don't seem to have this problem with quick sugars. I could have ice cream and chocolate and not crash at all.

Mixing tryptophan heavy foods (chicken / salmon / cheese / nuts) with carbs is gonna make you crash / sleepy.

Same thing with salted + carb heavy food, as the body starts putting on water (dry mouth, drinking loads, puffy + tired)