Optimum Nutrition Casein Protein Chocolate 924g. Support Muscle Growth & Repair Overnight. GOLD STANDARD 100% CASEIN is a slow digesting protein that supports muscle growth and repair while you sleep. Each serving is packed with 24 g of protein which provides a prolonged supply of amino acids overnight.. Our latest formula is now fortified with zinc which contributes to a healthy immune system and magnesium to support normal protein synthesis.. For overnight muscle support & repair. 24 g of premium whey protein per serving. Now fortified with Zinc & Magnesium