When you think of protein powder, what are the first two “types” that come to your mind? For many, it’s whey and casein protein. Why is that?

For about 2 decades now, supplement companies have hammered these two proteins down our throat. We have been taught to view them as almost two entirely different things, rather than just 2 different forms of high-quality protein (high in essential amino acids), which come from the same source (dairy protein), like they really are.

Now, am I saying there are no differences between these two proteins? Of course not. In fact, there are a few distinct differences between them, which may make one more beneficial over the other, depending on the scenario. In what scenarios would it be more beneficial to consume whey? What about casein? When does it not really matter either way?

Whey & Casein Proteins

I figured the best place to start this article, would be with a brief description about each type of protein to help lay the “ground-work” for our subsequent discussion.

As mentioned previously, both of these proteins are derived from dairy protein. To serve as a reference, bovine milk protein consists of 20-30% whey proteins, and 70-80% casein proteins. Both of these are “high-quality” proteins, in the sense that they both contain high levels of essential amino acids, however whey has a slightly higher leucine concentration.

Besides the difference in amino acid profiles, the main crux of the argument for varying the times one should consume one over the other, are centered around digestion rate.

Whey protein is water soluble, mixes easily and is rapidly digested (1,2). On the other hand, casein protein is water insoluble, coagulates in the gut, and is digested slower than whey protein (1,2). This is thought to be due to the presence of opioid peptides present in casein, which are thought to slow gastric motility (the movement and emptying rate of food in the stomach) (3).

Digestion Rate

To quickly summarize the findings of two studies (2,4) which each looked at digestion rate of proteins, and how this affected protein balance, here are some take-aways:

Whey protein rapidly increased amino acid concentrations in the blood, to a much higher level than casein protein (2).

than casein protein (2). Although the casein condition displayed a lower peak in blood levels of amino acids, it resulted in a much longer sustained elevation of amino acids (up to 7 hours) (4).

in blood levels of amino acids, it resulted in a much of amino acids (up to 7 hours) (4). Whey produced a larger increase in muscle protein synthesis (MPS), however it did not do much in-terms of decreasing protein breakdown (2).

in muscle protein synthesis (MPS), however it did not do much in-terms of decreasing protein breakdown (2). On the other hand, casein, although it didn’t cause as big of a “spike” in MPS, produced a marked decrease in protein breakdown (2).

To put it another way…

It was found that fast digesting proteins rapidly increased protein synthesis, but did little to depress protein breakdown, and had increased oxidation rates (the breakdown of the protein for energy), compared to slower digesting sources. The slow digesting proteins, slowly increased protein synthesis (and not to as great of a degree), however markedly decreased protein breakdown, and resulted in lower protein oxidation rates (the breakdown of the protein for energy), compared to the faster digesting proteins (4).

Overall, casein produced a GREATER whole-body protein balance than whey (2).

(There was one exception to this, however for the purposes of true, “real-world” practical application, it wasn’t particularly relevant.)

Case-closed, right? Casein wins the Bodybuilding.com “Protein Type” of the year award!!!.. Not so fast…

The Caveat (There’s always one, right?)

Although the above findings are great, there is only one small problem…they were conducted under fasting conditions, meaning there was no other food in the G.I. tract being digested/processed when these proteins were consumed.

So?

Well… the problem is, a majority of the time when we consume protein, it’s alongside other food sources. And because one food affects the digestion rate of all foods which are consumed, this can cause the above findings to be a bit misleading.

Even if it’s not necessarily in the same meal, other foods from prior meals can still affect the digestion rate of the next meal (or protein shake), because it can take up to 6 hours to digest a meal, depending on its constituents.

So, what happens when we add other food to the mix?

When either whey or casein proteins are combined with carbohydrates and fat, this slows digestion and time to peak amino acid levels (5). As with the previous studies we looked at (2,4) the amino acid levels still peaked and lowered to baseline at a more rapid rate with whey, however the differences were not as pronounced as when the proteins were administered alone (1).

One interesting note, was that protein balance was higher in both conditions (whey and casein), when these proteins were consumed alongside other nutrients, versus in isolation (partially attributed to the protein sparing effect of the additional energy) (5).

The addition of fat and carbs greatly decreased protein breakdown in the whey protein conditions (5). In fact, it was stated that this decrease in protein breakdown from consuming additional energy was so pronounced, that the enhanced protein balance of casein (from the result of less breakdown) is negated with the addition of energy alongside whey (1,5).

So essentially the addition of fat and carbs alongside the protein (as what typically happens with a meal) pretty much offset the protein-sparing effect of casein (because now there are other nutrients to serve that role), making the two (whey and casein), practically equal in regards to decreasing protein breakdown.

(As a side note, I also think it’s important to point out that the studies we examined today, looked at whole-body protein balance, not muscular protein balance itself.)

Filling-up the Rabbit Hole

So now that we’ve gone through the back-story, what the heck does all of this mean? Are there any generalizations we can take away from all of this? Yes.

Practical Applications

1) Both whey and casein are great sources of high-quality protein.

2) When consumed in isolation (without other foods, such as first thing in the morning after an overnight fast), either casein , or a whey/casein blend (shout-out to nature for already figuring this out when she created dairy protein), will probably be the better choice to go with over whey alone, in most scenarios, for enhancing total protein balance.

3) If consumed alongside other foods , either protein is a solid source, however because whey has a slightly higher level of leucine, it may actually serve as a slightly better choice because of its greater effect on muscle-protein synthesis. Either option works just fine though.

4) As we age, due to a variety of reasons, we become “less-sensitive” to the effects of protein. Because whey produces a greater “peak” in protein-synthesis (due to its higher leucine content), it may be a better choice for older adults, alongside the consumption of other food sources (to help with decreasing protein breakdown) (5).

5) In the end, the studies on whey vs casein that actually look at differences in performance and body composition are mixed in their results. Thus, overall it probably doesn’t matter in a mixed diet with a high enough protein intake (1.6g/kg+) whether you consume whey or casein despite their differential properties, unless they dominated your diet.

6) Lift weights, eat protein, have fun

I hope you benefited, and enjoyed reading this article. If there is anything you’d like me to write about in the future, feel free to reach out to me at: stevetaylorRD@gmail.com. You can also find me on:

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