There are more than 40 kinds of essential nutrients for human body, including carbohydrate, fat, protein, minerals, vitamins, cellulose and water. Among them, carbohydrate, fat and protein are called "three nutrients".

Nutrients can be divided into macronutrients and micronutrients according to the requirements of human body.

Macronutrients refer to nutrients whose daily requirement is greater than 1g, such as carbohydrate, fat, protein, water, potassium, sodium, calcium, magnesium, phosphorus and chlorine.

Micronutrients refer to nutrients with daily requirements ranging from a few millionths (micrograms) to a few thousandths (milligrams), such as iron, copper, zinc, cobalt, manganese, molybdenum, selenium, silicon, iodine, fluorine and some vitamins.