Taking 30 grams to 40 grams of casein 30 minutes prior to sleeping has been shown to have small but significant positive effects. It can improve muscle recovery, aid muscle protein synthesis (MPS), and may even increase metabolism.[1][2][3]
Casein supplementation in the evening could also cause a decrease in appetite the following day, which could be a useful tool for people trying to lose weight.[4][1]
A presleep bolus of protein (especially a slow-digesting protein like casein) can improve both body composition and athletic performance.[1] While these benefits are worth noting, it is important not to overestimate their significance. Daily calorie intake, total daily protein intake, and appropriate training are far more important in terms of body composition and performance goals.