If casein protein were in the gym, you'd probably find it spotting whey on bench press. Long seen as whey's less-glamorous partner, casein has been the Columbu to whey's Schwarzenegger.

Not today.

Here, we review the curious case of casein protein in-depth. Step into the courtroom as we judge what it is, how it works, and how it can help your goals.

Case Study: Casein Protein

Casein protein, like whey, comes from cow's milk. It accounts for roughly 80 percent of milk's total protein content, with whey constituting the other 20 percent. Casein is insoluble, which means it's the solid protein in milk.

You might hear casein referred to as calcium caseinate, which is a nod to the calcium ion associated with its protein structure. (If any gym rats ask you, now you can set 'em straight.)

In addition to being used as a supplement, casein's unique ability to gel has made it popular as a binder, filler, and a crucial part of the cheese-making process. Interestingly, casein's gel-power has also made it useful in plastics and glues.

Don't go eating that tube of Elmer's just yet. Casein supplements are a more effective way to get the protein you crave.

Case-in-Point: Casein Supplementation

Casein's crazy ability to gel and glob makes it a unique and diverse protein supplement. During digestion, casein gels as it hits stomach acid. This reduces the rate of digestion and allows for a slower, steadier, more efficient release and utilization of casein's amino acids. (Amino acids are the building blocks of protein.)

This basically means that your muscles receive a "trickle" of food over a longer period of time.

A slow digestion rate is also beneficial because it might reduce protein breakdown and amino acid oxidation--the burning of amino acids for energy. Casein can even increase your feeling of fullness, so you'll feel like you've got a full gut without having to carry one.

Casein And Whey: Gram To Gram

Casein can be a slow-digesting, double-edged sword, especially when compared to whey. On the plus side, casein's ability to slow down digestion extends the release of amino acids to muscle tissue and provides a more sustained boost to nitrogen balance. (A positive nitrogen balance is crucial to building muscle.)

However, casein's slow release of aminos also tends to reduce the body's peak anabolic response. This means that casein might not stimulate muscle protein synthesis as powerfully or quickly as whey. Because it digests slowly, casein is less anabolic (muscle-building) than whey when compared gram-to-gram.

Additionally, casein protein has a relatively low leucine content (8%) compared to whey (11%). Leucine is the amino acid responsible for the peak anabolic response to protein ingestion. Basically, leucine signals the body to stimulate protein synthesis and build muscle.

Research from my PhD thesis demonstrated that the anabolic response to a meal was closely associated with that meal's leucine content. Because casein contains less leucine than whey, it's not as directly anabolic.

Casein and Whey: A Match Made In Heaven

As discussed, casein doesn't provide whey's peak anabolic response, but it does provide a more sustained amino stream. To maximize this effect for the best of both worlds, consider combining casein with a rapid-digesting protein like whey. By doing so, you might benefit from high leucine plus a steady feed of amino acids.

Mixing a protein cocktail might allow you to reap the benefits of casein while potentially improving or overcoming some of its downsides. Alternatively, you could combine casein with rapid-digesting free-form BCAAs or leucine, which might offer a similar benefit.

Mixing a protein cocktail might allow you to reap the benefits of casein while potentially improving or overcoming some of its downsides.

Taking Casein 101

On its own, casein can be used by anyone looking to increase their overall daily protein intake. It's incredibly useful for those allergic to protein sources like whey or egg.

Casein, like whey, is easy to use and can be consumed any time of the day. However, due to casein's slow digestion and amino acid release, it's generally taken when you might be without food for a long period of time.

As such, many people prefer to consume casein at night with the thought that consuming a slow-digesting protein will help stave off catabolism (muscle breakdown). While there is little research examining the use of casein overnight, it has been shown to reduce protein breakdown and thus may be useful in such situations.

How much casein to consume depends on a number of factors like weight, total protein intake, and whether you're consuming it alone or with other protein sources.

Therefore, if you're taking casein alone, it can be beneficial to devour a large dose to try and maximize anabolism. I'd recommend 40 to 50 grams of casein protein (if consumed alone) for a 200-pound muscle-building male who wants to maximize the muscle-building response.

Casein, Shopping, And You

As a rule, I recommend purchasing supplements whose maker can provide lab analysis of their products. This ensures that what's on the label is actually in the bottle.

Also note that many companies sell protein blends containing both casein and whey. Since these blends are typically more expensive, remember that you can always craft your own casein-whey cocktail. Please, don't actually add any liquor. (If you do, go vodka.)

Safety First

A small number of people are actually allergic to casein protein. They might experience side effects such as upset stomach, pain, diarrhea, vomiting, and/or other GI problems.

Additionally, consuming large amounts of casein might cause a bit of digestive distress even in the non-allergic. Because casein gels, it can lead to a spot of bloating and general discomfort in mega-doses—especially for the people around you.

The moral of this story? Don't use casein protein if you're allergic, or if your physician has advised you against it. Furthermore, don't Hoover casein by the fistful unless you're shooting to feel like the Stay-Puft Marshmallow Man.

Casein Protein: Case Closed

Casein protein usually works the graveyard shift. People take it before bed, it works overnight, and then it fades from view as whey takes center stage.

Not anymore.

Use casein when you need a slow-digesting protein source. Use it to keep you satiated and your muscle satisfied. Use it with whey for the best of both worlds.

For all these reasons, get glued to casein.

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