The three major nutrients are sugar, fat and protein, which are nutrients for human beings and animals. All three substances can be obtained in food, but they are not stored in the same body organ.

Protein is the basic material for making cells and tissues. It is responsible for information transmission, maintaining brain activity, promoting chemical reactions, resisting foreign "invaders" and participating in human growth and tissue repair.

Sugar is the main source of human energy. 70% of the energy needed by the human body is provided by sugar. There are also sugars in human cell membranes.

The nutritional function of fat is to store and provide energy for human body. Fat releases twice as much energy as sugar and white matter.