Written by Victor R. Prisk, MD
17 December 2021

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CASEIN vs. WHEY: The Debate Continues

By Victor R. Prisk, M.D.


As one of the primary goals of Muscular Development is the dissemination of the most up-to-date information available in supplement science, the debate over the best protein type for supporting muscle protein synthesis, between whey and casein, continues to fuel a meeting of the minds. The fodder for this debate is based in the intrinsic difference in the absorption rates of the two protein types. Whey protein is a rapidly digested and thus rapidly absorbed protein that presumably leads to a more immediate rise in blood amino acid levels. Conversely, casein, also a milk-derived protein, has slower digestion and absorption rates and thus has a longer delay to peak amino acid levels in the blood, which are sustained over a longer period of time.


Whey and casein proteins, which are known for their high branched-chain amino acid (BCAA) content, are able to produce higher whole-body nitrogen retention and skeletal muscle growth after exercise and rest than soy protein.1 Research that we have previously reported on has demonstrated that the more rapid rise in amino acid levels after whey protein supplementation correlated well with a greater peak in muscle protein synthesis with post-workout consumption. However, newer research is challenging the notion that whey protein is the best protein to consume around the time of your workouts.


Newer Research


There is a subset of research projects looking into maximizing the effects of exercise in patients with chronic obstructive pulmonary disease (COPD), a condition that can arise from smoking, asthma, particulate exposure or congenital conditions affecting the lungs. It makes the work of breathing very hard and results in increased energy consumption, presenting as a thin and often frail patient. Low-intensity exercise in these patients without proper nutritional support can result in a greater than expected level of muscle protein breakdown and a severe deficit in anabolic responses to exercise.2 Although metabolic responses to exercise and protein supplementation in people with COPD are altered compared to the healthy, young weightlifter, newer research on casein versus whey protein supplementation sheds further light on this debate.


Scientists have manipulated their experimental protocols in an attempt to understand why the milk-based proteins may be more anabolic than soy-based proteins in people with COPD. First they manipulated the fact that soy is absorbed faster than casein by giving continuous feedings of the two proteins, thus stabilizing amino acid levels. Even with the absorption rate being factored out, patients with COPD had greater anabolic responses to casein than soy.3 Researchers then manipulated the BCAA content of soy protein to make it similar to casein. Again, even with the addition of BCAAs to soy, casein was still more anabolic than soy.3 By interpretation, this suggests that BCAAs are not solely responsible for the anabolic responses to casein protein.


Another study published in the journal Metabolismexamined whether casein is preferable over whey protein in optimizing the response in protein metabolism during and following a 20-minute bout of steady-cycle exercise in patients with COPD.4 First the researchers noted that patients with COPD had higher baseline protein turnover than control patients, and thus had higher resting energy expenditure. The higher resting energy expenditure is thought to be due to the energy expensive process of breaking down muscle. Physical activity and protein supplementation actually counteract the increased protein turnover, and limits the over-expenditure of energy that leads to skinny COPD patients.


The current study demonstrated that the net protein synthesis and thus muscle anabolism after whey consumption was lower than that observed for casein, despite similar protein and nitrogen loads in both COPD and healthy patients. This study tried to remove the confounding variable of absorption rate differences between whey and casein by providing the subjects with constant, small sips of the protein instead of a large bolus. To explain the difference in muscle anabolism between casein and whey, the scientists suggest that it may be related to the difference in types of BCAAs found in the two proteins. Casein tends to be higher in isoleucine and valine content, whereas whey has higher leucine content. Whether this is the source of the difference is yet to be determined. To study this, one would have to even out the variable BCAA content between the two proteins and reproduce the study just as was done for soy protein, as previously mentioned.


Best Protocol for You?


In conclusion, when whey and casein are consumed in sips such that the absorption rate of the proteins is removed from the equation, casein appears to be more anabolic. However, is this how we as athletes and busy individuals consume our food? We typically go about consuming our protein in large boluses before or after our workouts. Some research even supports intermittent intake versus constant intake of protein for maximizing protein synthesis. With so many variables in protein absorption, amino acid content, timing around exercise and the amount of intake, determination of the best protocol for you may take many more years of research. Perhaps the best way to figure it out would be to experiment on you. Change up your pattern of consumption and types of proteins consumed now and then. Try to monitor your body composition during a six-week schedule of one protein type versus another. Maybe you will find something different than the scientists?


Dr. Victor Prisk is a board-certified orthopedic surgeon and medical director of P.O.W. – Prisk Orthopaedics and Wellness, PC in Monroeville, PA. He specializes in regenerative medicine and foot and ankle treatment, and brings experience and empathy to his practice in the care of dancers, gymnasts and weight-training athletes. Dr. Prisk is an IFBB Professional League bodybuilder and judge, a member of the GNC Medical Advisory Board, and author of The GAIN Plan and The Leucine Factor Diet. For more information, visit https://www.orthoandwellness.com/





















1. Tang JE, et al. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistence exercise in young men. J Appl Physiol 2009;107(3):987-92.


2. Engelen MP, et al. Effects of exercise on amino acid metabolism in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2001;163(4)859-64.


3. Engelen MP, et al. Supplementation of soy protein with branched-chain amino acids alters protein metabolism in healthy elderly and even more in patients with COPD. Am J CLin Nutr 2007;85(2):431-9.


4. Engelen MP, et al. Casein protein results in higher prandial and exercise induced whole body protein anabolism than whey protein in Chronic Obstructive Pulmonary Disease. Metabolism 2012 Sep;61(9):1289-300.