I just finished reading Dr. Georgia Ede's book "Change Your Diet, Change Your Mind", which is very good, though I have been following most of her principles for 20-25 years. Getting rid of sugar, grains & legumes eliminated 99% of my brain fog, fatigue & joint pain. Back in the early 1990s when I was trying vegetarian & vegan diets "for my health" and was getting most of my protein from beans & lentils +/- cheese, a friend mentioned that I would often start a new sentence in the middle of my last sentence. I could hear myself doing it and cringed at how disjointed I sounded. At first I assumed I was just thinking faster than I could talk, but began wondering if the starch & antinutrients were causing inflammation &/or messing with my synapses such that I was literally "not thinking straight" or mis-ordering thoughts between my brain and my mouth. It went away when I went back to eating animal protein for clear and focussed thought and speech.