Milk can be broken up into two major protein groups. Casein makes up the vast majority of the protein content of milk (80%). The remaining 20% contains a group of proteins collectively known as whey proteins. Most of us here are very familiar with whey protein and believe it is an essential part of the bodybuilder’s collection of supplements. Whey protein is well known for its easy digestibility and rapid absorption, which is important immediately after a bout of exercise. However, less well known is the role that casein can play in building muscle.
Different Forms of Casein
There are different forms of casein, and they can be grouped as either soluble or insoluble casein. Depending on their solubility, these forms of casein have very different properties and applications.
Soluble casein includes calcium caseinate. Being soluble means that once calcium caseinate enters the stomach, it passes through rapidly, in a fashion similar to that of whey (Reitelseder, 2011). This form of casein is therefore valuable immediately postworkout, as a source of rapidly digestible protein which may complements that of whey.
Insoluble casein, such as micellar casein (found naturally in milk), has very different properties from calcium caseinate. This form of casein is insoluble and bind together in milk as micelles (hence the name “micellar casein”). Once micellar casein enters the stomach, they form large clumps, which take far longer to exit the stomach than the acid soluble whey proteins (Phillips, 2011) and soluble casein. There is no doubt that whey is a very high quality protein that has a great amino acid profile for bodybuilders, athletes, and people in general. However, it has been found that whey is digested and delivers amino acids too rapidly to sustain anabolic requirements many hours after ingestion (Lacroix et al, 2006). Micellar casein is excellent in being able to plug this hole, and provide a slow release of postprandial (after meal) amino acids for sustaining muscle anabolism. This can help to prevent muscle catabolism between meals.
Casein in Foods vs Casein Supplements
Casein is only found in dairy products. The cheese making process eliminates most of the whey proteins, leaving mainly casein. Consequently, cheese is a good source of casein. However, cheese is often also quite high in fat. This makes it less popular among bodybuilders as a casein source. A good alternative is cottage cheese, which is low in fat and high in protein. A low fat cottage cheese has around 12g protein (most of which is casein)/100 g. The unfortunate thing about cottage cheese is that it is often not to everyone’s taste. Furthermore, the cost of 100 g cottage cheese works out to be around $1.20 for a popular brand. To get the same amount of protein from a popular casein supplement, it costs only $0.85. Therefore, a powdered casein supplement may be more favourable to your tastebuds and wallet.
What to Look For in a Casein Supplement
Both forms of casein are readily available, and on the front of the label, the product may not be specific as to which type of casein is present. However, as the properties and functions of casein differs greatly according to their solubility, it is important to know which type you are getting. If you are looking for a rapidly absorbed protein to complement your whey, then calcium caseinate may be the one for you. Typically they can be found in products such as weight & mass gain supplements. If you are looking for a source of protein consumed a few hours after a workout, to top up muscle fuels, and protect from catabolism, be sure to look for a product that contains micellar casein. Micellar Casein is commonly consumed before bed & is regarded as the king of night time protein, during a period in which you are unable to provide additional amino acids to your muscles. A popular food source of casein for this purpose is cottage cheese, but of course that is not always to everyone’s taste. In which case, a powdered casein supplement may be more to your liking. Furthermore, because casein supplements are more concentrated, you will not have to sit for hours on end downing tubs of cottage cheese.
Lacroix et al (2006), Compared with casein or total milk protein, digestion of milk soluble proteins is too rapid to sustain the anabolic postprandial amino acid requirement. Am J Clin Nutr, 84: 1070-1079.
Phillips (2011), Comparison of whey to caseinate. American Journal of Physiology. Endocrinology and Metabolism, 300: E610.
Reitelseder (2011), Whey and casein labeled with l-[1-13C]leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion. American Journal of Physiology. Endocrinology and Metabolism, 300: E231-E242