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Whey vs. Casein: The Ultimate Protein Rivalry?

If you are in the fitness world or cautious about your health you may have heard about the long-term battle about which protein supplement is better: Whey or Casein. I am here to settle the score. But before jumping in, let's lay the foundation:

Both of these proteins are derived from milk. Whey protein makes up 20% of the milk protein and Casein makes up the other 80%.(1) Both can naturally be found in cheeses and yogurt and are also found fortified into protein bars or protein shakes. Both of these proteins are of the highest quality (a term that will soon be described) and offer many benefits to athletic performance and recovery, as well as health benefits surrounding weight loss.

Origin of Whey Protein

There are two forms in which whey protein is commonly found: whey protein concentration (WPC) and whey protein isolate (WPI). Whey protein concentrate and whey protein isolate refer to protein content. Whey protein concentrate contains about 35-80% protein whereas Whey protein isolate contains about 90% protein.

High quality

Whey protein is a high-quality protein supplement. The label “high quality” when referring to protein means that the protein supplement contains all of the essential amino acids and branched-chain amino acids. Other protein supplements like plant-based supplements, for example, may not contain all of the essential amino acids and will thus receive a lower quality rating.

Examples of amino acids found in Whey Protein:

  • Leucine

  • Lysein

  • Phenylalanine

  • Isoleucine

  • Methionine

  • Threonine

  • Tryptophan

  • Valine

  • Histidine

Bioavailability of Whey Protein

Another benefit of whey protein is that it is highly bioavailable. The term highly bioavailable means that the body can easily utilize this type of protein. When something has a low bioavailability other metabolic factors, including intestinal pH, genetic variability in enzyme activity, and the presence of other dietary constituents such as inhibitors prevent the body from fully metabolizing it. (2) For example, leucine is a bioavailable branched-chain amino acid in whey protein that plays an important role in muscle building.


When compared to casein, whey protein is digested quickly by the body. This feature can be beneficial depending on individual goals. For an athlete who is trying to increase their calorie/protein intake, a faster digesting protein may be better versus a slower digesting protein such as casein which will keep them feeling fuller for longer.

Origins of Casein Protein

Casein protein, like whey protein, is originally sourced from milk and can be found in various cheeses, yogurt, protein powders, and protein bars, as mentioned earlier.

Casein protein can also be found in infant formulas.

Quality and Bioavailability of Casein Protein

Casein and whey protein both score as high-quality proteins meaning that they both contain all nine essential amino acids. Casein is also similar to whey protein in that it is one of the most bioavailable forms of protein and can easily be digested.


The difference between whey and casein is their rate of digestion and amino acid availability. Casein protein is a “slow” protein, meaning that it digests and releases its amino acids much slower than whey protein.(3)

This characteristic can be very beneficial, especially for those with specific health or fitness goals. For example:

Weight loss

Those who are attempting to lose weight may want to consider the digestion and bioavailable benefits that casein protein offers.

Because this protein source is slow to digest, gastric emptying (or the rate at which your stomach uses the food in it) is much slower. This

increases satiety leaving you

feeling fuller for longer.


For those who live with diabetes the rate at which blood sugar spikes is very important. A protein that digests slowly enters the bloodstream slowly preventing harsh spikes in blood glucose levels, something that is very dangerous for those living with diabetes.(4)


Digestion rate is not the only benefit of casein protein. Studies have also shown that Casein is linked to increased calcium absorption, again bringing us back to the idea of bioavailability. However, this time the protein is helping the body properly metabolize calcium. This feature of casein can be very beneficial to older adults as bone health becomes an important topic of discussion with increasing age. This feature of casein is also beneficial to those fighting to prevent osteoporosis. (5)

Which should you Choose?

When it comes to choosing the winner between Whey vs Casein the final result is actually a tie. Whey and Casein protein both offer their own unique benefits but there are no studies that prove one is more beneficial to muscle gain, amino acid availability, and post-workout recovery.

When making your choice:

1. Define your health goals

  • Increased calorie and protein consumption

  • Decrease calorie consumption

  • Need for calcium absorption

2. Financial Factors

  • Consider your budget, keep in mind that one protein source may be more costly than the other

3. Method of Consumption

  • Consider how you plan to consume the protein. If you prefer a quick shake that you can fill with water, whey protein may be a better choice because it is water soluble and will mix well. Casein, on the other hand, is not water-soluble and will mix better with milk.

In summary, there is no clear winner between these two protein options, it is crucial that you consider your own health and lifestyle goals when making your choice. Consider your calorie needs, your health goals, your budget, and your method of consumption.



  1. Hemant G, Mayur C, Pooja P, et al. Whey protein. Scholars Res. J. 2011: 1(2): 69-77. DOI:10.4103/2249-5975.99663

  2. Gropper SS, Smith JL, et al. Advanced Nutrition and Human Metabolism. 8th ed. Cengage Learning. Published 2021.

  3. Wilborn CD, Taylor LW, Outlaw J, et al. The effects of pre- and post-exercise whey vs. casein protein consumption on body composition and performance measures in collegiate female athletes. J Sports Sci Med. 2013;12(1):74-79.

  4. Westphal S, Kästner A, Taneva E, et al. Postprandial lipid and carbohydrate responses after the ingestion of a casein-enriched mixed meal. The American J Clinical Nut. 2004; 80(2): 284-290.

  5. Snyder BS, Haub MD. Whey, casein and soy proteins. Sports Nutrition: Fats and Proteins. CRC Press. 2007; 144-159.

Additional Interesting Resources:

  1. Whey protein and pressure ulcer wound healing


    2. Farsaei S, Samimi S, Abbasi S, Taheri A. The topical formulation of whey protein for the prevention of pressure ulcers in critically ill patients: A novel intervention in a randomized-controlled clinical trial. Advanced Biomedical Research. 2023;12(1):168. doi:10.4103/abr.abr_302_22.

  2. Whey vs. Casein in Weight loss


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