Casein-Hydrolysate Beats Whey as Intra-Workout Protein: Faster Time-Trial Times vs. Water, Non-Sign. Performance Boosts Compared to CHO, Whey & Whey + CHO Beverage

Whey or casein hydrolysate - or rather no protein - what to use in your intra-workout beverage for endurance?
Last week, SuppVersity reader Oscar Qiu asked me which protein supplements I would suggest he'd buy. My answer was simple: "Get a cheap whey protein and if you want to spend extra money, add some micellar casein. Dose it at a ratio of 20:10 whey:casein post-workout (learn why) and, if you feel you're not getting enough protein on a daily basis, optionally, take them at a ratio of 10:20 whey:casein right before bed" (learn more about pre-bed casein).

Now, I am not going to revise this basic supplementation advice I gave based on the results of a recent study from the University of the Witwatersrand (Oosthuyse. 2015), but it may still be worth considering that other protein sources like whey-hydrolysate (learn more) or, as in this case, casein-hydrolysate may have certain context-specific benefits over the aforementioned "staple proteins".
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In said study, Oosthuyse et al. tried to find the "protein most suitable for ingestion during endurance exercise" (Oosthuyse . 2015). To this ends, the researchers compared the effects of co-ingesting either
  • 15 g/h whey-hydrolysate with (whey-CHO) or without carbohydrates (whey-PLA) or
  • 15 g/h casein-hydrolysate with (casein-CHO) or without carbohydrates (casein-PLA).
In conjunction with the placebo, only, and the carbohydrate, only, trials there are six trials, i.e. placebo, placebo+whey, placebo+casein, the 63g/h fructose: maltodextrin (0.8:1) that made up the CHO content of the test beverages, alone, and in conjunction with either whey or casein-hydrolysates.
Table 1 + 2: Dietary records (mean ± SD) for 2 days preceding the day of each experimental trial (left); composition of the experimental beverages consumed during the trials (right | Oosthuyse. 2015).
Practically speaking this meant that 2h after the last meal (postprandial), 8 male cyclists ingested either: carbohydrate-only, carbohydrate-whey-hydrolysate, carbohydrate-casein-hydrolysate or placebo-water in a crossover, double-blind design during 2 h of exercise at 60 %Wmax followed by a 16-km time trial.
Why would you even want to consume protein during endurance exercises? As the authors point out, the mechanisms by which protein supplementation during exercise may potentiate endurance performance are (1)providing additional oxidative, gluconeogenic and anaplerotic substrate, (2) reducing endogenous protein catabolism (Korach-Andre. 2002; Koopman. 2004), (3) reducing exercise-induced muscle damage (Saunders. 2005, 2007 & 2009), (4) improving rehydration (Seifert. 2006) and (b) possibly delaying central fatigue (Skillen. 2008). While all of these potential mechanism are backed up by isolated studies, the results are far from being unambiguous with conflicting evidence being presented in several studies and reviews (Cermak. 2009; Breen. 2010; Hobson. 2015). The study at hand does however add a new perspective to the research by evaluated whether the addition of protein to a carbohydrate energy drink will affect exercise metabolism and specifically the rate of oxidation of the co-ingested carbohydrate, as well as using different forms of protein. With whey and whey hydrolysate being the predominantly used forms of protein in previous studies, it is thus well possible that the conflicting evidence would have been less conflicting if all studies had used casein hydrolysate instead.
Data were evaluated by magnitude-based inferential statistics and revealed only non-significant effects on carbohydrate oxidation, measured from 13CO2 breath enrichment, by either of the two protein hydrolysate in isolation (data not shown),
Figure 1: What really counts are the performance improvements (left) and potential gastrointestinal side effects during (right, c), yet not so much right after the time-trial (right, b | Oosthuyse. 2015).
This changed, when the carbohydrates came into play: While the increased carbohydrate availability obviously lead to increases in glucose oxidation in all trials, these increases were substantially decreased (98% very likely decrease) when the carbohdrate drink was co-ingested with casein-hydrolysate (mean ±SD, 242 ±44; 258±47; 277 ±33g for carbohydrate-casein, carbohydrate-whey and carbohydrate-only, respectively). As it was to be expected, this decrease in carbohydrate oxidation during exercise had to be compensated by increases in fat oxidation - in this case a 93% likely increase from 83 ±27 and 73 in the whey-carbohydrate and carbohydrate-only to 92 ±14 g in the casein-hydrolysate group.

Figure 2:  Hydro whey and hydro casein have only slightly different amino acid makeups - *indicates essential amino acids (Oosthuyse. 2015).
Now, some people who are still believing in the long-overcome theory of exercise-induced fat loss may speculate that the increased fatty oxidation in the casein group would indicate that the co-ingestion of casein-hydrolysate would increase exercise-induced fat loss. You, as a SuppVersity reader know that the assumption that increased intra-workout fat oxidation would equal increased fat loss is total bogus. Accordingly, you will appreciate that the addition of casein to the intra-workout equation did have additional, practically relevant benefits: It lead to a significantly faster time trial ( − 3.6%; 90 % CI: ±3.2%) performances compared to placebo-water (95 % likely benefit).

Ok, now that you've hopefully memorized that you can safely ignore the non-existent fat-loss benefits of increased fat oxidation during exercise (assuming it is just to compensate a reduced CHO oxidation, as in this case), you must be careful not to jump to the similarly unwarranted conclusion that the time-trail times in Figure 1 would indicate that you or the (endurance) athletes you may be coaching should exchange all their "Gatorades" and other CHO-based intra-workout beverages for pure casein-hydrolysates.
Tired, exhausted, had to cut your workout short today? Is it the flu, or just too much BCAAs?
Don't flush all your Gatorade down the toilette, ... yet: For one, there are still issues with bloating and thirst during, as well as intestinal cramps after the workouts when you co-ingest protein and carbohydrates. More importantly, however, the performance increase the researchers saw with in the casein-hydrolysate trial reached statistical significance only in comparison to the water-placebo trial. The benefits were non-signifcant, even when casein was compared to carbohydrates, only. This does not negate that the study at hand suggest that you should prefer hydrolyzed casein over whey-hydrolysate as an intra-workout protein source. What the study certainly does not tell you, thouh, is that all athletes should replace their carbohydrate containing intra-workout beverages with water + casein-hydrolysate - even if the contemporary carbohydrate scare may make this non-alternative appealing.

Before making a final statement about "the optimal intra-workout protein source", it would also be necessary to know exactly what's responsible for the advantage - it could be the higer amount of glutamine in casein vs. whey, which could help curb the increase in ammonia during high intensity exercise (Bassini-Cameron. 2008) - a problem due to which consuming large amounts of BCAA supplements during exercise may actually do the opposite of what the shiny ads will tell you. It could yet also be any other difference in the amino acid make-up, the absorption kinetics or the peptide structure of whey- vs. casein-hydrolysates that explains the difference | Comment on Facebook!
  • Bassini-Cameron, Adriana, et al. "Glutamine protects against increases in blood ammonia in football players in an exercise intensity-dependent way." British journal of sports medicine 42.4 (2008): 260-266.
  • Breen, Leigh, Kevin D. Tipton, and Asker E. Jeukendrup. "No effect of carbohydrate-protein on cycling performance and indices of recovery." Med Sci Sports Exerc 42.6 (2010): 1140-1148.
  • Cermak, Naomi M., et al. "Muscle metabolism during exercise with carbohydrate or protein-carbohydrate ingestion." Medicine and science in sports and exercise 41.12 (2009): 2158-2164.
  • Hobson, Ruth, and Lewis James. "The addition of whey protein to a carbohydrate–electrolyte drink does not influence post-exercise rehydration." Journal of sports sciences 33.1 (2015): 77-84.
  • Koopman, RenĂ©, et al. "Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise." American Journal of Physiology-Endocrinology and Metabolism 287.4 (2004): E712-E720.
  • Korach-Andre, Marion, et al. "Differential metabolic fate of the carbon skeleton and amino-N of [13C] alanine and [15N] alanine ingested during prolonged exercise." Journal of Applied Physiology 93.2 (2002): 499-504.
  • Oosthuyse, T., M. Carstens, and A. M. Millen. "Whey or Casein Hydrolysate with Carbohydrate for Metabolism and Performance in Cycling." International journal of sports medicine (2015).
  • Saunders, Michael J., Mark D. Kane, and M. Kent Todd. "Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage." MEDICINE AND SCIENCE IN SPORTS AND EXERCISE. 36.7 (2004): 1233-1238.
  • Saunders, Michael J., Nicholas D. Luden, and Jeffrey E. Herrick. "Consumption of an oral carbohydrate-protein gel improves cycling endurance and prevents postexercise muscle damage." The Journal of Strength & Conditioning Research 21.3 (2007): 678-684.
  • Saunders, Michael J., et al. "Carbohydrate and protein hydrolysate coingestion's improvement of late-exercise time-trial performance." International journal of sport nutrition 19.2 (2009): 136.
  • Seifert, John, Joseph Harmon, and Patty DeClercq. "Protein added to a sports drink improves fluid retention." International journal of sport nutrition and exercise metabolism 16.4 (2006): 420.
  • Skillen, Rebecca A., et al. "Effects of an amino acid-carbohydrate drink on exercise performance after consecutive-day exercise bouts." International journal of sport nutrition 18.5 (2008): 473.
Disclaimer:The information provided on this website is for informational purposes only. It is by no means intended as professional medical advice. Do not use any of the agents or freely available dietary supplements mentioned on this website without further consultation with your medical practitioner.