Both whey protein and casein protein are derived from milk, but there is a dramatic difference in their absorption rate. Whey protein is a fast-digesting protein, boosting protein and amino acid levels within minutes of ingestion. This also means that it is utilized quickly by the body, leaving your body hungry for more in a short period of time.
Casein protein, on the other hand, is a slow-acting protein that takes a few hours to digest. But once it does, its effects last for several hours longer than whey protein, creating a long-lasting, optimal environment for muscle synthesis.