Optimum Nutrition Gold Standard 100% Casein Protein Chocolate 1.8kgGOLD STANDARD 100% Casein supports muscle recovery during nighttime and between meals with 24g of premium micellar casein protein. Micellar casein protein is derived from milk and digests slower than whey protein. The result is a protein option that allows your body to absorb protein and amino acids over longer periods of time when eating is not possible or practical such as during sleep or between meals.