Here’s an easy way to rev up your brain health. Drink coconut water. It’s high in potassium, a mineral that’s important to brain function. People who don’t have enough potassium tend to have a slower rate of brain activity. Bananas (medium-sized) have more potassium than coconut water—but also more calories. To benefit, all you need is about one cup of coconut water daily. You also can add it to smoothies and mix it with milk.