If you treat your car well, you give it high-octane fuel. This boosts engine performance. Similarly, the right selection of foods boosts brain power.
The brain's main source of fuel is glucose, an end product of carbohydrate metabolism, which is used by the cells for energy. Glucose is fed to the brain via the bloodstream. But, although glucose is a form of sugar, we shouldn't eat candies and chocolate to ensure its presence in the bloodstream.