The two most popular supplemental powder forms of protein, whey and casein, are both milk proteins, but is one better or worse than the other? Well, frankly, they both have some merit and application in many instances, especially when we are concerned about performance and physique enhancement.
Given this, we will take a look at what the pros and cons are to both whey and casein protein powders, what the research shows about each, which instances are best suited to each, and who should consider using them.
Whey and casein: Difference in digestive rates
Most people generally refer to whey and casein proteins as the “fast” and “slow” digesting proteins, respectively.
When we talk about the slow digestion rate of casein, we are essentially saying that it will raise blood amino acid levels slowly and for an extended period of time versus whey protein, which does the inverse. Therefore, many people find that ingesting a whey protein promptly after exercise is best since it provides an acute, intense elevation of blood amino acids and thus muscle protein synthesis.
Casein, on the other hand, is generally reserved for periods of time when people know they won’t be able to eat for a lengthy period of time and need a protein that is slowly releasing amino acids into the blood stream.
That being said, studies seem to suggest that mixing protein sources may provide advantage over relying on one, single source repeatedly. The delayed gastric emptying rate of casein and high leucine content of whey can provide a sustained elevation of protein synthesis for several hours after ingestion, an effect not observed with solely whey protein ingestion since it is digested rather rapidly.  This is why dairy milk is a popular beverage of choice for many individuals who are looking for whey and casein proteins.
While the digestion rates do differ between whey and casein, there are several other factors to consider when it comes to these proteins.
Whey and casein: Assessing the amino acid content
One such factor to take into consideration is the amino acid profile of whey and casein proteins. While both of these proteins are considered “complete”, whey protein does contain a larger proportion of leucine, which appears to be a key regulator of muscle protein synthesis. 
This isn’t to say that casein lacks a nominal amount of leucine (or other essential amino acids) for muscle protein synthesis, but just that you will need a larger amount of casein on a per gram basis to ingest the same leucine content as a pure whey protein.
This chart below shows both the biological value (BV) and the protein digestibility corrected amino acid score (PDCAAS) of various protein sources. The former refers to a measurement that assesses the degree to which an animal is able to utilize that protein while the latter is a number between 0 and 1 that evaluates protein quality based on amino acid content in relation to human’s requirements for them:
|Whey Concentrate and Isolates||104-159||1.00|
As you can see, the PDCAAS for both whey and casein are equivalent, but the BV of whey proteins can be more than two times the value of casein.
However, in the bigger picture, the BV doesn’t necessarily mean that all the protein sources that have lower values aren’t useful. Consider that many bodybuilders and physique athletes alike rely heavily on seafood, beef and chicken for the majority of their protein intake and still maintain a large amount of muscle tissue. This is just a point in case that as long as you’re getting a variety of animal and animal-derived protein sources the BV is not too much of a concern. The exception would be for vegans who rely heavily on plant proteins, which is another topic in and of its self.
Whey and casein: Calcium content
Calcium is oft touted for it’s beneficial effects on bone health and may also assist the fat loss process. Calcium is a generous component of casein micelles and thus is more abundant in casein protein supplements than whey protein supplements.
Micellar casein protein contains roughly 3x the amount of calcium when compared to an equivocal amount of whey protein (concentrate and isolate). For individuals who struggle to meet their daily calcium quota through food sources, casein protein supplementation can be an easy alternative to calcium supplementation.
Whey proteins do contain some calcium as well, but it is considered a minimal component. This is yet another reason that a blended protein containing both whey and casein proteins may be the best bang for your buck (more on this below).
Whey and casein: Texture and use in food applications
Some people may not have much concern for using their protein supplements as part of food recipes and just prefer the good ol’ shaker cup and water method, but it is becoming increasingly popular for individuals with culinary imaginations to create some pretty fantastic foods that incorporate protein powders.
When considering the texture of casein protein powder, it tends to be a bit “fluffier” and coarser than whey protein powder. Also, whey protein powder’s texture will vary based on its protein content and the method of filtration used. Generally, pure whey isolates are very fine powders, almost like sand, while some whey concentrates with higher fat and carbohydrate content are less fine and more “chalky”.
As far as their applicability in food recipes and baking, it is often advised to stick to whey protein when you plan on actually cooking something since casein protein will not solidify thoroughly when heated and could leave baked products mushy and falling apart.
Many people find that they like to make cold recipes, like puddings and yogurts, with casein protein since it mixes much thicker than whey protein does and absorbs more water content.
For more information on recipes using whey protein and casein protein powders, check out the M&S recipes section here.
Should I use whey, casein or both?
Ultimately the most pertinent question to answer is which of these proteins is most appropriate for health enthusiasts and physique competitors alike. As we have broken down some of the advantages of each in the previous sections of this article, it would be asinine to claim that one is unanimously superior to the other given that certain instances may be better suited for one or the other (or both) and will vary depending on the individual in question.
That being said, I think it’s safe to say that a blended protein that contains both casein and whey proteins would be an effective supplement for most any time of the day or situation. Reason being is that these proteins tend to compliment each other so that you ultimately are getting the best of both worlds.
Moreover, it’s become lucid that the idea of needing fast-absorbing whey protein immediately prior to and/or after training isn’t really founded on much more than dogma. The bigger issue is just simply taking in a sufficient, quality protein source in a decent timeframe after training has occurred.
Another factor to take into consideration is that concomitant ingestion of other nutrients can significantly alter the digestive rate of whey and casein proteins. Whey protein may absorb rather rapidly on its own, but if you eat a bunch of fibrous veggies and unsaturated fats along with it (which delay gastric emptying) than it could take hours to completely digest and utilize that protein. This is why it’s improper, if not impractical, to say that whey should always be used around training time and casein at other times because many people eat other foods when they take their protein supplements.
If you can’t pick one or the other, it might be best to choose a protein supplement that contains a variety of protein sources to sort of “cover all your bases”. You don’t have to buy separate whey protein and casein protein supplements if that doesn’t fit your budget, but if you can afford it than it’s safe to say there is plenty of use for both in your supplement stash.
1) Drummond MJ, Dreyer HC, Pennings B, Fry CS, Dhanani S, Dillon EL, Sheffield-Moore M, Volpi E, Rasmussen BB. Skeletal muscle protein anabolic response to resistance exercise and essential amino acids is delayed with aging. J Appl Physiol. 2008 May;104(5):1452-61.
2) Reidy, P. T., Walker, D. K., Dickinson, J. M., Gundermann, D. M., Drummond, M. J., Timmerman, K. L., & Rasmussen, B. B. (2013). Protein blend ingestion following resistance exercise promotes human muscle protein synthesis. The Journal of nutrition, 143(4), 410-416.