1) Cut out refined sugars and try to consume natural sugars from fruit, this will keep your Glycemic Index (GI) levels stabilised. Fruit can be juiced to make smoothies, along with vegetables, nuts & seeds. Just be aware of the amount of fruit intake due to fructose content and sugar is sugar! It is good to eat a piece of whole fruit sometimes as this contains more fibre.
2)Keep foods natural, meaning no processed foods, this would be fruit, veg, beans, pulses, protein and some dairy.
3)Good fats such as avocado, olive oil & oily fish are very beneficial and help feed the brain, as our brains are made up of 60% omega 3 fats.