in my personal experience, eating chocolate has pushed me into IBS trouble, which i realized such a disease existed after 15 years. I stopped eating chocolate for the past 5 years. Now i am happy.
Brain is a sugar sucker. Eat food which has natural sugar (like fruits) and you still be happy. Chocolate is just one sour junk which sugar added to please your bain (which is the trick). I think eat the chocolate without sugar and see if it sill improves brain function