100 percent Casein Protein from Optimum Nutrition:

Low Carb Slow Digesting, Anti Catabolic Miceller Protein With Glutamine!

Sometimes slower is better - especially when it comes to the rate of protein digestion. While rapid protein absorption is desirable immediately before or after exercise, delayed release is probably more beneficial throughout the remainder of the day. Casein proteins are pH sensitive and gel in the acidic environment of the stomach. As a result, it can take more than twice as long for caseins to be broken-down into their amino acid subcomponents than whey and other proteins. Casein is the most abundant protein present in milk. It is considered a high quality protein because it is easily assimilated and it supplies sufficient quantities of amino acids that cannot be synthesized by the body.

Another benefit is increased satiety (feeling of fullness or satisfaction). Casein exerts a slight pressure on the stomach walls. In effect, this pressure signals to the brain to stop eating because the stomach is full. Casein is the most slowly digested and absorbed type of protein. This helps create a "timed-release" effect, providing a steady stream of amino acids to your muscles over a long period of time. The net result is a greatly enhanced anti-catabolic environment which is much more friendly to growth and recovery.

Bodybuilders and athletes looking to build lean muscle, prevent muscle breakdown, and reduce recovery times, and individuals interested in improving the quality of their sleep can greatly benefit from casein.

Casein Research

Perhaps the most interesting kernel on casein to come from the scientific community is the Boirie study, which found that casein managed about a 31% increase in protein synthesis (to whey's 68%)... but also reduced whole-body protein degradation (catabolism) by 34%. More importantly, researchers found that casein contributed to a positive nitrogen balance an average of 7 hours after ingestion.

The Biorie study has since spurred further research of casein. Another study looked at the effect casein might have on body composition when used as part of a 12-week weight-training program. Participants were separated into two groups, each of which maintained a balanced diet including 75 grams of protein per day. The difference was in the sources of protein used: while the first group relied on whey-based drinks to reach their daily protein requirements, the second group made use of milk protein isolates (80% casein, 20% whey). At the end of the study, the milk protein isolate group had lost more fat (15.4 lbs. vs. 9.2 lbs.), gained more lean mass (9 lbs. vs. 4.4 lbs.), and gained more upper and lower body strength than the whey group.