Milk contains all vitamins known to date. Fat soluble vitamins such as A, DE, K; water-soluble vitamins such as B, C, niacin, biotin, pantothenic acid, choline, folic acid, etc. Vitamins are a large class of nutrients necessary for maintaining life and health. Although the amount is very small, they are very important for maintaining normal growth of the human body and regulating its physiological functions. Therefore, when any kind of vitamin is deficient, it may cause some disease, even death. The human body cannot produce vitamins, and the vitamins needed are all taken and supplemented from food.

The minerals in milk are also called inorganic salts or ash. In addition to hydrocarbon, oxygen and nitrogen, they mainly include calcium, magnesium, sodium, potassium, phosphorus, chlorine, sulfur, etc. The calcium content is very high, 110 mg per 100 grams of milk. Although the amount of minerals in human body composition is very small, it is indispensable. For example, calcium in blood is the main material to form bones and teeth, and can also help blood coagulation to maintain normal myocardial activity. The inorganic salts in milk can also maintain the normal physiological functions of the body. For example, the proportion of calcium and phosphorus is suitable for forming bones, and the proportion of potassium and sodium is suitable for maintaining the osmotic pressure of body fluid and the acid-base balance of body fluid.

Lactose is a unique component in mammalian milk, and the sweetness of milk comes from lactose. The content of lactose in milk is 4.6% - 4.7%. Lactose is almost completely dissolved in milk. Although lactose belongs to carbohydrate, its nutritional value is greater than other carbohydrates. Galactose is very important for infant intellectual development. It can promote the production of brain lipids and mucopolysaccharides. Lactose can also promote the growth of lactic acid bacteria in the human intestinal tract, thereby inhibiting the adverse effects caused by abnormal fermentation in the intestinal tract. Lactose is related to calcium metabolism, so drinking milk is beneficial to calcium absorption. Lactose also provides heat for the body.

Milk fat is one of the main components of milk, and its content in milk is generally 3% - 5%. The fat in milk is mainly composed of short chain and medium chain fatty acids. Since the melting point of milk fat is lower than human temperature, and it has a good emulsification state, milk fat is a kind of edible fat with high digestibility. Fat is an important component of human body, which can assist absorption of fat soluble vitamins. Milk fat contains all known oil soluble vitamins, among which vitamin A and carotene are very high.

Milk protein is one of the main components of milk, with the content of 2.9% - 3.3%, which is mainly composed of casein and whey protein. Milk contains all essential amino acids. One liter of milk can meet or exceed the daily requirement of essential amino acids for adults, so milk protein is called "complete protein" and the best protein. The digestibility and absorption rate of milk protein is very high, generally 90% - 100%, and the digestion speed is also faster than that of meat, eggs, fish, bread, etc.