Micellar casein is an insoluble form of casein that is revered for its slow release properties. The term "micellar" refers to the fact that these proteins naturally aggregate into "micelles" when in a watery medium.
Micellar casein is the primary protein content of cow's milk. In fact, it makes up 80% of the total protein of milk, while the remaining is whey protein. Consequently it can be found in milk and milk products such cheese and yoghurt.
Micellar casein is a very high biological value protein that forms clumps when it enters the stomach, and hence is very slow digesting (Phillips, 2011). This results in a slower release of amino acids into the body, which is beneficial for periods in which food is no longer being consumed. It has been shown that four hours after ingestion of whey protein, branched chain amino acids (BCAAs) are no longer being supplied to the body, while micellar casein was still able to supply BCAAs at this time (Lacroix et al, 2006). Furthermore, significantly higher concentrations of leucine (a BCAA) can be found in circulation seven hours after consuming micellar casein compared to whey protein (Boirie et al, 1997).
MIcellar casein is a naturally occurring substance in milk, and is consumed in large amounts by many people. It is safe to eat casein and most people do not often experience side effects. However, if you are lactose intolerant, it is important to note that there may be significant levels of lactose present in products containing casein. Likewise, if you have a milk allergy or intolerance, casein may not be appropriate for you.
One downside to micellar casein is that because it is so slowly absorbed, it is not ideal to use it as a post workout supplement. The absorption of micellar casein is much slower than that of whey protein (particularly a hydrolysed whey), and is therefore not as effective in stimulating muscle synthesis (Tang et al, 2009).
The recommended dose for micellar casein is no different to that of other protein. This has been covered in detail in our "Recommended Protein Intake Per Day" article. Basically, aim for around 1.5 to 2 g protein/kg body weight. Consume micellar casein in doses to meet these requirements.
Ingredient timing is important for micellar casein protein. As mentioned above, it is not the ideal protein for as a post workout supplement. However, it can be used throughout the day to provide a steady supply of protein. It is also the ideal protein to use before bed to help maintain anabolism through the night.
When looking for a micellar casein supplement it is important to note the difference between micellar casein and calcium caseinate. The difference has been covered in our "Casein Protein" article. Long story short, calcium caseinate is actually soluble in the stomach, and it does not possess the same slow digestive properties as its micellar casein sibling.
Micellar casein supplements are readily available and are often marketed as "night time" proteins, because they are great to take before bed. They can also be found in milk protein powders, weight gainers, blended proteins, and protein bars.
Micellar can be stacked with other forms of protein such as whey and soy protein to give a complementary effect.
Boirie et al (1997), Slow and fast dietary proteins differently modulate postprandial protein accretion. PNAS, 94: 14930-14935
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.
Tang et al (2009), Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol 107: 987-992