Casein protein powder is best used before going to sleep at night and a serve of 25-30 grams for active people is a good amount to use. However, for those without an active lifestyle, casein can actually be converted to fat stores to some degree. Casein is best used in combination with whey after a workout. At night it has the ability to reduce muscle cell breakdown as you sleep by providing a constant slow release of amino acids into the bloodstream.