Protein in milk, whey protein is the fastest and most effective absorption, while casein is slowly digested and absorbed in the body. Although it is not as fast as whey protein and can be used by the body, it can ensure the environment for muscle growth in the body for a long time. Whey protein has fast digestion and absorption rate. Generally, it can be quickly decomposed into amino acids and enter the blood within 1-2 hours after ingestion, and basically digested in 3-4 hours. It can be replenished and absorbed more quickly after fitness and training, help the body to quickly open and recover, and quickly synthesize the damaged muscle fiber tissue after training, thus achieving the effect of increasing muscle. Therefore, fitness enthusiasts or athletes have a great demand for whey protein.