Whey + Casein - A Superior Post-Workout Shake in Theory (Fast + Slow) and Practice (Results of a 10-Week Study)

Casein & whey - Many companies sell both. For a good reason!
It appears to be logical. By combining whey and casein in your post-workout shake you would have the protein synthesis triggering spike of amino acids from the whey and the long-lasting pro-anabolic hyperaminoacidemia (=elevated amino acid levels in the blood) from casein. Can you ask for more?

Yes, you can! You can ask for scientific evidence that this is actually superior to say spiking your whey protein with additional pro-anabolic BCAAs (Atherton. 2010; Blomstrand. 2001) and allegedly recovery boosting glutamine (Sharp. 2010).
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Luckily, Kerksick, et al. did exactly this study in 2006, already. It's quite interesting that it is rarely cited, which is why I think it's worth its own SuppVersity post despite the fact that it's already 9 years old. Ah... well, and of course it's also worth being cited because it's a 12-week (10 weeks training time) resistance training + supplementation study that does not fool us to believe that whey + BCAA may be superior, because the researchers failed to measure the actual muscle gains in a long(er) term study.
Table 1: Overview of the resistance training protocol the subjects followed for 10 weeks after
an acclimatization phase of 2 weeks (Kerksick. 2005).
As the authors point out, "the purpose of this study was to examine the effects of whey protein supplementation on body composition, muscular strength, muscular endurance, and anaerobic capacity during 10 weeks of resistance training" (Kerksick. 2006). Thirty-six resistance-trained males (31.0 +/-  8.0 years, 179.1 +/- 8.0 cm, 84.0 +/- 12.9 kg, 17.8 6.6%) followed a 4 days-per-week split body part resistance training program for 10 weeks.
No, adding BCAAs to your intra-workout will not increase your gains: The previously cited study by Blomstrand et al. (2001) does not just show that the ingestion of BCAAs post-workout can increase protein synthesis. It does also prove that doing the same intra-workout may be tasty, but not productive.
Table 2: As you can see, the supplements were isocaloric. Differences in the energy intake from the supplement, which had be consumed as quickly as possible, but ideally within 2 hours, following the workouts on training days and in the morning ( 9:00 AM) of nontraining days, can thus not explain the different study outcomes (Kerksick. 2006)
Three groups of supplements were randomly assigned, prior to the beginning of the exercise program, in a double-blind manner to all subjects (see Table 1 for details):
  • 48 g per day (g·d 1) carbohydrate placebo (P), 
  • 40 g per day of whey protein + 8 g per day of casein (WC), or 
  • 40 g per day of whey protein + 3 g per day branched-chain amino acids + 5 g L-glutamine (WBG). 
At 0, 5, and 10 weeks, subjects were tested for fasting blood samples, body mass, body composition using dual-energy x-ray absorptiometry (DEXA), 1 repetition maximum (1RM) bench and leg press, 80% 1RM maximal repetitions to fatigue for bench press and leg press, and 30-second Wingate anaerobic capacity tests.

Now what's most interesting for us, obviously are additional effects of the supplements on the body composition of the study participants - despite identical total energy and protein intakes (2.1g/kg body weight both the WBG and WC groups).
Figure 1: Changes in lean and fat mass over the course of the 10-week training period (Kerksick. 2006).
An effect of which the data in Figure 1 tells you that it was the most significant for the WC group. Ok, after the 5-weeks mark the gains stagnated, but in the whey + amino acid group, the subjects even lost the lean mass they'd gained. Quite interesting, by the way, because this coincided with a reduction in volume and an increase in weight... so could it be that training in the higher rep ranges is eventually more anabolic? Well, to prove that we would have to do another study.
Protein Requirements of Dieting Strength Athletes: More is Better Only in the Presence of Adequate Carb & Fat Intake. Optimal Muscle Retention With 2-3g/kg Lean Body Mass | more
What this study shows, is not that training in a higher rep range of 10 reps per set is more anabolic than training in the 6-8 range. What the study at hand shows is that the combination of plain whey and casein proteins is vastly superior to the funky "BCAA-powered" and "glutamine enhanced" protein powders you will see in the stores and in shiny advertisments.

And let's be honest, in view of the way the fast and slow digesting proteins facilitate long-lasting elevations of amino acids in the blood (=hyperaminoacidemia), the results of this study are not exactly surprising | Comment on Facebook!
  • Atherton, Philip J., et al. "Distinct anabolic signalling responses to amino acids in C2C12 skeletal muscle cells." Amino acids 38.5 (2010): 1533-1539.
  • Blomstrand, Eva, and Bengt Saltin. "BCAA intake affects protein metabolism in muscle after but not during exercise in humans." American Journal of Physiology-Endocrinology And Metabolism 281.2 (2001): E365-E374.
  • Chad M., et al. "The effects of protein and amino acid supplementation on performance and training adaptations during ten weeks of resistance training." The Journal of Strength & Conditioning Research 20.3 (2006): 643-653.
  • Sharp, Carwyn PM, and David R. Pearson. "Amino acid supplements and recovery from high-intensity resistance training." The Journal of Strength & Conditioning Research 24.4 (2010): 1125-1130.
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