Slow and Steady Wins the Race: Casein Protein 101

There are a wide range of protein powders available on the market and it often becomes confusing to identify what does what and when you should use them.  Casein protein is one of those that you would find a lot of people not knowing much about. A lot of it is hearsay so we present to you an educational piece on the details and benefits of casein protein. Let us dive right in.

What is casein protein?

Casein protein is a slow-digesting protein that is well known for being the “time-release” protein. What this means is that casein protein takes a longer period of time to digest in the body.

Casein protein comes from milk (mainly cow milk) and is the insoluble portion of milk that serves as 80% of milk protein. The other 20% of milk protein is whey protein. The difference between the two would then obviously be its solubility and digestion speed (whey being the fast-digesting protein while casein is the slow digesting portion).

Part of what makes casein protein a great protein source is that it is a complete source of protein. This means that it contains all essential amino acids that your body needs for muscle tissue repair and growth. Additionally, it contains a large variety of unique bioactive and protein compounds which have tremendous benefits for your muscle tissue repair health.

There are mainly two types of casein protein available:

  • The more common kind of casein protein is known as micellar casein. This is the version that is slow digesting and the one that most folks buy specifically for its slow digesting purposes.
  • The less popular version which is known as casein hydrolysate. This form of casein has been pre-digested and is one that is rapidly absorbed by the body. Also, it does not taste so great.

Why casein is so popular amongst the hardcore crowd.

In a nutshell, because of its timed slow releasing qualities, casein has been used as a valuable source of protein to fill in during long periods of not eating.

A lot of pro and diligent bodybuilders will use casein’s slow digesting properties as a source of protein to prolong muscle protein synthesis in the body. Furthermore, it will aid your cells in synthesising protein during periods that one would typically consider catabolic.

According to a study conducted by Boirie Y et al[i], it is suggested that the large and rapid spike in leucine threshold (an amino acid vital to the initiation of muscle protein synthesis) when ingesting and digesting whey is met with an equally rapid drop in this state, resulting in the activation of muscle protein synthesis being lost soon after. Casein on the other hand has demonstrated a steadier and more prolonged period of muscle protein synthesis due to its gradual digestion rate.

Now when it comes to building muscle, it cannot be over-stated that casein works great as a muscle building source and aid. It contains extremely high levels of leucine (the amino acid responsible for Initiating muscle protein synthesis). And just to toot the horn of the casein train, Demling et al[ii] found in their study that that a group that was given casein group had experienced double the muscle growth and triple the fat loss compared to the group that they had given whey protein (under certain controls, of course). Furthermore, the group that had used casein had also experienced more fat loss than the group who had been given whey.

What makes casein another great source of protein is that due to its ability to keep your body in a more prolonged state of muscle protein synthesis. Muscle protein synthesis and muscle protein breakdown are processes that occur daily and often and in tangent with one another. To oversimplify, the net result of one or the other will either result in total muscle lost or total muscle gained. Keeping your body in a more prolonged state of muscle protein synthesis is a great way to stave off the breakdown and works best to retain your muscle even during a heavy cutting cycle. Furthermore, and for this reason, casein is often used at night to prevent the protein breakdown that may occur, since you go through a relatively long period without food while you sleep.

In one study conducted by Tim Sniiders et al[iii], it was observed that a casein protein shake taken before bedtime helped strength-training men increase their type 2 muscle fiber size while additionally adding gains to both their performance and strength in their subsequent days in the gym.

The verdict

Casein protein is a great and complete source of protein that has a host of benefits for its users. It does come with small side effects like bloating (due to its non-soluble nature) and some water retention, but it definitely helps keep your fuller and provides you with a more stable release of protein. However, this will not count for anything if your diet and the rest of your protein and nutritional needs are not met throughout the day. Casein is excellent but it can only help so much. Therefore, get your diet right and supplementing it with casein protein will make you a powerhouse in the days to come.


[i] Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrère B. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci U S A. 1997 Dec 23;94(26):14930-5. doi: 10.1073/pnas.94.26.14930. PMID: 9405716; PMCID: PMC25140.

[ii] Demling RH, DeSanti L. Effect of a hypocaloric diet, increased protein intake and resistance training on lean mass gains and fat mass loss in overweight police officers. Ann Nutr Metab. 2000;44(1):21-9. doi: 10.1159/000012817. PMID: 10838463.

[iii] Tim Snijders, Peter T Res, Joey SJ Smeets, Stephan van Vliet, Janneau van Kranenburg, Kamiel Maase, Arie K Kies, Lex B Verdijk, Luc JC van Loon, Protein Ingestion before Sleep Increases Muscle Mass and Strength Gains during Prolonged Resistance-Type Exercise Training in Healthy Young Men, The Journal of Nutrition, Volume 145, Issue 6, June 2015, Pages 1178–1184,

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