Nutrition is a reasonable food for human beings to repair old tissues, proliferate new tissues, generate energy and maintain physiological activities. Substances in food that can be absorbed and utilized by the human body are called nutrients. Sugar, fat, protein, vitamins, water and inorganic salts (dietary fiber is called "the seventh nutrient") are six kinds of nutrients needed by human body. The first three kinds of nutrients generate energy after metabolism in the body, so they are also called productivity nutrients. Its main function is to form the body and provide energy.
The six nutrients needed by human body are: sugar, oil, protein, water, inorganic salts and vitamins. Among them, sugar, protein and fat are substances that supply human energy. The six nutrients mainly come from nine categories of food: cereals, eggs, milk, roots, meat, fish, shrimp and shellfish, beans, dried fruits, vegetables and fruits.