The mind needs rest and sleep for our systems to rebuild cells and to produce energy.

In order to do this fuel, must be applied in the form of food, for man cannot think without eating, and so we find that even a spiritual activity such as thinking cannot be converted into sources of pleasure and profit except by making use of material means.

The Master Key, Charles Haanel 19:15

Scientists have proven through research that students who are emotionally upset or hungry when the come to school do not perform as well in the classroom as those who come from a stable environment and have eaten breakfast.

Also, studies have found that drinking water during the day and keeping the body always hydrated produces a better learning environment for the mind to work in the thinking process.