Casein is a slow-digesting dairy protein that people often take as a supplement. It releases amino acids slowly, so people often take it before bed to help with recovery and reduce muscle breakdown while they sleep. Several studies have shown it helps boost muscle growth, along with a ton of other benefits. Casein is a versatile powder that can be enjoyed a number of ways. If you’re looking for a quick dose of casein, you can mix it with milk or water as a shake. Or if you aren’t a fan of shakes, you can bake casein into several different things, such as bars, muffins, cookies, for a healthy treat before bed.