Bodybuilders have known for years that whey is a fast-digesting protein ideal for postworkout recovery. Some are also taking hydrolyzed whey protein, which is absorbed faster than standard whey because it is “predigested,” a process that breaks the long protein chains down into short protein fragments. The athletes also know that casein is a slow-digesting protein more suited for nighttime, since the slow digestion rate prevents your body from breaking down muscle while you sleep. However, recent research has shown that adding casein to your postworkout shake can lead to enhanced gains in muscle mass compared to whey alone. And now that hydrolyzed casein protein is available for purchase, and is as fast digesting as hydrolyzed whey, you may wonder if this is a better option than a standard casein, such as micellar casein or caseinates, after workouts. The answer? It depends.


In a clinical study conducted by French researchers, 21 male and female subjects were given a 700-calorie weight-gainer shake with large amounts of carbs, fats and protein. One group received the shake with hydrolyzed casein as the protein source while the second group received the shake with whole casein as the protein source (approximately 27 grams of protein each). Results found that the group receiving the whole casein protein had higher levels of muscle protein synthesis, the process that results in muscle growth. More of the protein in the hydrolyzed group was used for non-muscle-building functions.

In a second study that measured the effects of hydrolyzed and whole casein protein when no other calories were given, opposite results were found. The results of this study show that when taken by itself, more casein protein is used for musclebuilding purposes when consumed in the hydrolyzed form.


Choosing the right type of casein to add to your postworkout whey depends on what your goals are. If you are looking to keep carbohydrates and calories under control in order to build muscle while also dropping bodyfat, then add a hydrolyzed casein protein to your whey shake along with no more than 20 to 30 g of carbs, and zero to little fat.

On the other hand, if you are a hardgainer looking to pack on as much mass as possible, add whole casein protein, such as micellar casein or caseinates, to your postworkout whey in addition to higher levels of carbohydrates and fats. You can add fast-digesting carbs (such as dextrose) along with the protein from whole milk to achieve this, or look for a weightgainer powder that contains all of these ingredients.

Whole milk has high levels of fat and also has an 80/20 ratio of casein to whey as the natural protein sources. Although conventional bodybuilder wisdom says to stay away from fat after a workout, it appears that casein protein has a synergistic effect with fat that results in increased muscle building. Not only was this the case in the previously mentioned French study, but an additional study found that when taken after weight training, whole milk resulted in increased muscle protein synthesis over skim milk.