Whey vs. Casein

The whey is the best known of the "new generation" proteins. In just a few years, it has become an essential nutritional supplement in fitness and bodybuilding. However, there is a second milk protein that is much less famous but just as strategic: CASEIN! Comparing whey and casein, we find great similarities (high biological value, high nutritional quality). However, these two proteins, although from the same dairy source, do not behave the same way. They differ essentially in their rate of assimilation: whey is quickly assimilated while casein is slowly broken down. These two proteins with different behaviors complement each other perfectly to provide a synergistic effect when combined in a sports nutrition program. The notion of protein assimilation rate originates from a study conducted by Boirie [4]. For the first time in 1997, he demonstrated that the blood availability of amino acids directly depended on the type of protein ingested. Whey induces a rapid but brief increase in plasma amino acid levels. Casein, on the other hand, was responsible for a slow but prolonged increase in aminoacidemia. Boirie attributes this difference in behavior to the slower gastric emptying rate for casein due to digestive coagulation.

WHEY

Access product: Performance Protein

Whey is the "Queen" post-workout protein. It is a fast protein with an anabolic action that perfectly meets the protein synthesis needs triggered by physical exertion. It has the highest biological value; it is the food protein whose amino acids are the most assimilable [1].

Of all the proteins commonly used by athletes, whey is the richest in cysteine, the amino acid precursor of glutathione (a powerful antioxidant). It is a protein rich in branched-chain amino acids (BCAAs), particularly leucine (10 to 12g per 100g). Nearly 20% of whey's amino acids are BCAAs, the foundational amino acids of muscle fibers.

Sports wheys are filtered to varying degrees from milk and then dehydrated to obtain two protein-rich, low-fat and low-lactose versions: isolate and concentrate. The difference between these two forms is a matter of a few nutrients for similar performance.

There is a third form of whey: the hydrolysate. The whey hydrolysate is certainly the fastest version since the protein has been partially broken down, but it is also the most processed and least digestible form. Enzymatic hydrolysis profoundly alters the functional characteristics of the whey that served as the base. If there is native whey concentrate or isolate, hydrolysates are by definition denatured [3]. Regardless of the type obtained, the objective is always the same: to have a positive effect on protein turnover by ensuring complete and rapid muscle amino acid delivery!

*N.B.: Lactose intolerance is the inability to digest large amounts of lactose (the predominant sugar in milk). This inability results from a deficiency in the lactase enzyme responsible for hydrolyzing a large part of the lactose present in milk into glucose and galactose.

CASEIN

Access product: Pure Native Micellar Casein

Casein is the main protein in milk. It represents 80% of its protein content. It is a slow protein with an anti-catabolic action that slows down protein breakdown (proteolysis) [2]. Casein has an excellent biological value and is fully digestible. It is a protein particularly rich in glutamic acid, arginine and tyrosine. It also contains significant concentrations of BCAAs.

Sports caseins come in 3 types: caseinate, micellar casein, and casein hydrolysates.

The presence of caseinate in a supplement is a sign that it is a low-end formula. It is an old generation casein that has become completely obsolete. It has been replaced by micellar casein, also called "total milk protein". Its amino acids are much easier to assimilate and its duration of action is prolonged compared to caseinate, which is advantageous for better muscle protection against catabolism. Hydrolysates, on the other hand, have completely lost their anti-catabolic properties and are ineffective in this context [5].

The slow assimilation of casein is mainly due to a slow gastric emptying rate. Indeed, in contact with the acidic digestive medium, casein precipitates, which delays the action of the digestive enzymes responsible for its decomposition. This peculiarity gives casein its strategic anti-catabolic properties. Taking casein 30 minutes before bedtime balances the overall protein metabolism during nocturnal recovery and stimulates muscle protein synthesis [6,7].

By acting slowly, casein releases a continuous and prolonged flow of protein-forming amino acids. In this way, it protects the muscles from nocturnal nutritional catabolism. It is the protein of the night but also an excellent protein junction between meals. Its high satiety-inducing power also makes it an excellent protein source in fat loss and muscle definition programs.

Comparison: Whey vs. Casein

Criteria	WHEY	CASEIN
Action	Anabolic (Stimulates synthesis)	Anti-catabolic (Slows down breakdown)
Assimilation	Fast and brief	Delayed and prolonged
Bioavailability	10 to 15g / hour	5g / hour
Biological Value	100	86.6
Amino Acid Profile	Rich in BCAAs	Rich in Glutamine, Arginine, Tyrosine
Ideal Timing	Morning / Post-training	Bedtime / Between meals

Amino Acid Profile (g/100g)

Amino Acids	WHEY	CASEIN
Isoleucine*	5.9	4.3
Leucine*	10.4	7.9
Lysine	9.1	6.6
Methionine	2.1	2.2
Phenylalanine	3.1	4.2
Threonine	7.1	3.6
Tryptophan	1.8	1.0
Valine*	5.1	5.3
Histidine	1.8	2.2
Alanine	4.9	2.6
Arginine	2.4	3.0
Aspartic Acid	10.8	6.0
Cysteine	2.3	0.5
Glutamic Acid	17.8	18.2
Glycine	1.7	1.5
Proline	5.9	8.4
Serine	4.9	4.7
Tyrosine	2.9	4.5
*BCAAs 2:1:1	21.4%	17.4%

Strategic Conclusion

The timing of intake throughout the day means that one protein in particular is superior to another. This notion of assimilation rate is very interesting for athletes but has no interest for sedentary individuals.

Combining whey and casein within a sports nutrition program is a strategic act, as these two proteins with different properties complement each other to provide a synergistic effect far superior to isolated consumption. It would therefore be a shame not to fully exploit the properties of milk proteins.

In a program, the "pro-anabolic" whey will constitute the ideal post-training snack. The "anti-catabolic" casein will complement this program by slowing down nocturnal nutritional catabolism thanks to a slow and prolonged coverage in protein-forming amino acids.

Scientific References:

[1] Sindayikengera S. et al. J Zhejiang Univ Sci B. 2006.
[2] Frühbeck G. Nature. 1998;391(6670):843–945.
[3] Valdemiro CS, et al. 4th International Conference of Food Science and Technology. 2000.
[4] Boirie, et al. Proc Natl Acad Sci U S A. 1997.
[5] Frédéric Delavier. Guide des compléments alimentaires pour sportifs. Vigot. 2015.
[6] Trommelen J. et al. Am J Physiol Endocrinol Metab. 2018.
[7] Res P.T. Med Sci Sports Exerc. 2012.
[8] Olsen, et al. J Physiol 2006.