Optimum Nutrition Casein is a 7 hour digesting protein ideal for use before bed or as a meal replacement. Because during the night is when your body will typically do most of its growing it is important to make sure that your muscles are fuelled with everything they need for recovery. However most food protein and other protein powders will be completely digested within just a few hours. This means that your body does not have a supply of the nutrition that it needs for a large portion of the night. Supplementing casein can make a big difference to your body’s ability to recover at night. 100% Casein also has a great taste and is perfect to crush your cravings for desert.