Casein protein is a slow-releasing protein with great muscle fueling potential. It features properties that slowly release amino acids into the bloodstream to feed muscles. It naturally provides key amino acids, such as glutamine and branched chain amino acids, so casein protein is excellent between meals and before bed for sustained amino acid delivery. As an ideal nitrogen-fueling supplement, this casein formula to help fuel your musclesﾒ previous supply of nitrogen, since your muscles can only grow when your body is in positive nitrogen balance. GNC Pro Performanceﾮ 100% Casein Protein provides support for powerful anti-catabolic signals for efficient muscle fuel.