Protein is a necessary macro nutrient that serves many purposes in the body, the most important of which is muscle building.
There are two main classes of protein; whey and casein. Whey protein is a fast absorbing, fast acting, very high quality protein that provides the most benefit when taken immediately before or after exercise. Casein protein is a slow acting protein that provides a sustained release of amino acids into the blood stream, so that they can be used more efficiently by the body. It is beneficial to include both of these forms of protein in your diet, weather you exercise or not.
Whey protein can further be broken down into two categories; concentrated and isolated whey. The most popular form of protein supplements are protein powders. Most protein powders will include a combination of both isolated and concentrated whey. Isolated is the more pure and more expensive from of protein. It is essentially whey concentrate, put through a second purification process. Whey concentrate still contains some fat, carbohydrates and cholesterol, where as whey isolate has all of these things filtered out; It is almost pure protein by weight. Drinking a protein shake before or after a workout and weight training in particular, will help your body recover faster. It is best to take whey protein within 30 minutes of a workout to get the most benefit out of it.
Casein protein is another popular choice for protein powders because it also helps your body recover from workouts, but it can be taken at any time of the day. Bodybuilders take casein protein before bed to keep their bodies in an anabolic state while they sleep. The body will go into a catabolic state (muscle break down) when it doesn’t have calories or protein for an extended period of time. Taking casein protein will help preserve muscle tissue by providing an extended, time release stream of amino acids into the blood. Milk is made up of 80% casein protein and 20%whey protein, so it is a good substitution for a casein protein powder.
Combining a diet and supplement plan that includes both of these types of protein will benefit athletes and non-athletes by helping maintain and increase muscle mass. To simplify things you can purchase a high quality protein complex that includes both casein and whey protein.