|Whey or casein hydrolysate - or rather no protein - what to use in your intra-workout beverage for endurance?|
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).
|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).|
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).|
|Figure 2: Hydro whey and hydro casein have only slightly different amino acid makeups - *indicates essential amino acids (Oosthuyse. 2015).|
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.
- 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).
- 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.