A healthy diet is rich in fruits, vegetables, fiber, lean protein and "good" monounsaturated and polyunsaturated fats in moderation.

What's more, participants' whose diets were highest in polyunsaturated fats from fish as well vegetable oils reduced their risk for dementia.

The authors of that 2015 credit a pistachio’s monounsaturated and polyunsaturated fatty acids for the nut’s health perks.