As far as foods that aren’t so great for your brain, ultra-processed foods (i.e. cookies, candy, fast food, etc.) earn the top slot. These foods tend to be nutrient-poor, calorically-dense, and high in sugar, salt, and/or fat. Red meats17, foods high in saturated fats18, sugar19, and sodium20 can also harm brain health, Maxwell says, due to their negative impact on the gut microbiome and heart functionality.