Casein takes a long time to digest, unlike whey. These absorption differences make casein better for use before going to bed, while whey is better for u003ca href=u0022https://www.tnhealth.org/fitness/best-pre-workoutsu0022 target=u0022_blanku0022 rel=u0022noreferrer noopeneru0022u003epre-workoutsu003c/au003e.