Protein is also essential, but you don't always need protein shakes to get your share. It depends on your goals. When you work out, your muscles develop tiny micro-tears, which help them to grow bigger and stronger. That's where protein comes in, helping your body to repair and develop, so you can get results or put on muscle mass. While beef, chicken and fish are all good sources, there are plenty of veggie options, including dark green vegetables like spinach or broccoli, as well as lentils, quinoa and seeds.