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".
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.
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.
References:

• 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, René, 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).
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• 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.