A Simple Guide to Slow-Digesting Protein


With thousands of brands of protein powders all having a supposedly unique use, how is a person supposed to know what to use for their goals? There are fast proteins, slow proteins, designer proteins, protein blends, weight gainers, plant protein, Branch Chain Amino Acids, Essential Amino Acids, etc. If you’re wary of the sales pitch from your local GNC sales clerk that ends with “trust me, bro, it increases the size of your bench-press-gastroc-ubula muscles by 11,000% and we just happen to have it on sale for 256 dollars,” then this article may be of use to you. 

I wonder if they will allow me to pay using a home equity line of credit...

I wonder if they will allow me to pay using a home equity line of credit...


What is “Slow-Digesting” Protein

First off, someone may want to know what slow-digesting protein even means? How do we differentiate between slow and fast? There are no exact criteria for this, what generally constitutes slow-digesting protein are going to be micellar casein, milk, milk concentrate, egg white, egg, or any whole food protein source. Plant protein powders like pea, often fall into the slow categories, also. The wheys and various isolates and hydrolysates are going to be proteins that encompass the faster-digesting spectrum.

If we were to compare just whey and casein proteins, which are both derived from dairy, one of the differences would include the amino acid profiles, with whey having more leucine. This is significant because leucine absorption is a powerful signal for muscle protein synthesis (building muscle). Another difference is their structures from processing. When casein is denatured it begins to coagulate, this coagulation leads to what is essentially a clump of protein that takes longer to break down and this is where the slow-digesting properties come from. 

Why Would We Use It

Slow and steady wins the race, right? Or is it speed kills? There really isn’t a right or wrong protein to use, it just depends on what goal you are trying to accomplish with that specific supplement. 

Slow-digesting protein is often labeled “anti-catabolic” which I think is doing it a disservice. The idea behind anti-catabolic is that slow-digesting protein is absorbed at a rate which doesn’t induce much muscle protein synthesis, but does an excellent job of preventing muscle breakdown. The ensuing slow trickle of amino acids in the bloodstream promotes a positive nitrogen balance that is needed for muscle maintenance.

However, research shows that casein is actually quite effective at inducing muscle protein synthesis by itself, and even more effective when combined with whey into a blend. 

When to Use It

The standard recommendation for slow-digesting protein is to use before bed. This allows for your body to be exposed to a slow and steady stream of amino acids while you are sleeping. Having an amino acid supply during sleep can help to facilitate recovery and muscle repair. 

Slow-digesting proteins can work well at other times, too. If you are a light eater in the morning, a shake of slow-digesting protein can help to get amino acids in your bloodstream along with providing satiety until lunch time. On recovery days slow digesting proteins could be used anytime to promote muscle repair in the same manner that consuming it before bed does.

If there was a time to avoid slow-digesting protein it would be in the peri-workout window, meaning before, during or immediately after. This is because fast-digesting proteins may be more beneficial for spiking your bloodstream with amino acids which can promote enhanced absorption into muscle cells during workouts. 

Slow-digesting proteins may limit the amount of amino acids in your bloodstream diminishing the cellular uptake of aminos and ultimately reducing muscle protein synthesis during the workout window. 

What to Look For

Micellar Casein - Derived from dairy - this is going to be your slowest digesting protein. Legend says Micellar Casein digests so slowly that Frodo refused it on the grounds that he was hoping to have an empty stomach by the time he reached Mordor.  

One protein to rule them all..

One protein to rule them all..


Milk Concentrate - Milk is naturally comprised of 80% casein and 20% whey. Therefore, milk and milk concentrate protein powders are going to be primarily slow-digesting. 

Egg - Is a nice alternative to dairy with better bioavailability than casein (bioavailability basically means how well it can be absorbed). Whole egg protein will digest slower than egg white protein due to the inclusion of the naturally occurring fats. Consequently, those fats also help whole egg to edge out egg white in the bioavailability index. Another reason to eat the damn yolk. 

Plant (pea, hemp, soy, etc) - Non-animal protein is typically slow-digesting. Even soy is on the slower side. Unfortunately, plant proteins also rate much lower in bioavailability because that’s how plants roll. They don’t have legs or teeth, so they have other mechanisms to protect themselves. Some of those mechanisms, like fiber and anti-nutrients, reduce our ability to absorb nutrition from plants. Nothing against choosing to be vegetarian or vegan, but seriously, if you’re trying to build muscle, maybe don’t choose a protein source that has the absorbability of my counter-top. 

Blends - Most of the time, what you will find in protein powders are blends of different proteins, such as micellar casein, whey isolate, egg white, etc. The idea of the blend is to take advantage of each protein's unique and beneficial properties. The slow-drip of micellar casein and the speed and bioavailability of egg and whey make for a versatile and effective protein. If you can work with dairy, I would recommend a blend like this for most scenarios outside of the workout window. 

Really though, choose blends. Blends are idiot proof.


Slow-digesting proteins are just another tool in the toolbox, but knowing how and when to use that tool can help you increase your recovery capacity and build muscle. 

Now when your grandma brings you those milk and cookies be sure to impress her with your knowledge of milk protein content and ratios. I am certain there is a high chance she will walk away signing your praises, "what a smart grandkid I have" as opposed to "Billy is still an insufferable douche".  

Meh, probably more like 50-50.

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Click the picture to check out some of our original shirt designs!