Given that the brain is 60% fat, it’s no surprise that dietary fat influences cognitive function. In the brain, myelin sheaths, a layer of insulation around nerve fibres that allows neurons to send signals quickly and effectively, are mostly made of fat. It is recommended to consume two servings of “oily fish” and seafood per week, such as salmon, tuna, trout, mussels, oysters, herring, mackerel, or sardines.