Protein is the name off the game when it comes to muscle growth and maintenance, but there are so many different types of protein that you may wonder which ones are best. Whey and casein are two of the most common protein supplements, and are considered the gold standard. They are different proteins that act in different ways, but they are two sides of the same coin.
Milk Proteins
Whey and casein are both milk proteins. Whole milk consists of about 13 percent solids, 27 percent of which is protein -- casein makes up about 80 percent of the protein, and whey is the other 20 percent. Imagine a bowl of cottage cheese -- the thin liquid part is the whey, the chunky solid part is mostly casein. Both are healthy protein sources, but their different characteristics make them useful for different things. Being milk products, neither whey nor casein are suitable for vegans.
Whey
Whey protein digests quickly, dramatically boosting the amino acid levels in your blood within 20 to 40 minutes. Many bodybuilders drink a whey protein shake after a meal to help the protein enter the bloodstream quickly, while the whole food from the meal helps extend the release of additional protein. This provides a steady, ample stream of amino acids to the muscles to prepare them for a strenuous workout. Whey protein is sold as either an isolate or a concentrate -- the isolate is generally more expensive, but it contains at least 10 percent more protein than the concentrate form, and is so low in lactose that it is commonly tolerated by the lactose-intolerant.
Casein
Casein is a very slow-digesting protein that provides a gradual, steady release of amino acids. It should never be used before a workout or with a meal, because it stays in the digestive system for 3 to 4 hours and can slow the digestion of other foods; however, it is ideal as a muscle recovery drink. Consuming a casein shake after a resistance workout can prevent the breakdown of muscle tissue, allowing the amino acids to go toward building new muscle instead of repairing damage. Casein is highly digestible, but it contains more lactose than whey and may not be suitable for the lactose intolerant.
Practical Use
Because milk contains both casein and whey, it may seem like the best way to get both proteins. While low-fat milk is very good for you, it contains such a small amount of whey and casein that it's better to use a supplement if these particular proteins are important to you. Both are available as premixed shakes or as powdered mixes, and are mainstays of the bodybuilder's kitchen. Even if you only work out casually, a casein shake after a gym session can help you progress faster by avoiding muscle degradation from both resistance and cardio work.
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