|No, I don't think the results would have been different, if the subjects had been young women. For older guys and gals, on the other hand, I am not 100% sure.|
The intention of the researchers was (yet again) to "characterize the dose-response relation of postabsorptive rates of myofibrillar MPS to increasing amounts of whey protein at rest and after exercise in resistance-trained, young men", (Witard. 2014). This is nothing new, but still right up the average SuppVersity reader's alley, I suppose.
So what about the study design
The design of the study was simple. The 48 healthy volunteers consumed a standardized, high-protein
(0.54 g/kg body mass) breakfast. Three hours later, they all performed a standardized bout of unilateral exercise, consisting of 8x10 leg presses and leg extensions at 80% of their individual, predetermined one-repetition maximum. "Immediately" (max. 10min) after they were done with the leg workout the volunteers consumed
- 0g, 10g, 20g, or 40g whey protein isolate
- postabsorbtive rates of myofibrillar protein synthesis (MPS) ,
- whole-body rates of phenylalanine oxidation and
- urea production
Now that you know all the important details about the study design, it's almost time to take a look at the results. Before we finally do that, let's just briefly recapitulate the results of (Cuthbertson. 2005) who observed that 10 g EAAs at rest and (Moore. 2009b) who observed that 20 g egg protein after exercise were "optimal for the maximal stimulation of MPS in young adults". This is after all, what the researchers hypothesis that "20 g of whey protein (~10 g EAAs) would be sufficient for the maximal stimulation of myofibrillar-MPS rates at rest and after resistance exercise in trained, young men" (Witard. 2014) was based on.
We are talking about statistical significance here: I know what you are going to tell me, now. And yes, you are right. The protein synthesis was in fact higher, but that's more of a matter of how sustained the increase was and not a matter of a "faster" protein synthesis. In other words, with 20g of a fast absorbing whey protein and a whole meal with slow absorbing proteins 30-40min after you will achieve the same - if not higher muscle protein synthesis rates in the long(er) run (>2h)... ah, and by the way: The response in the untrained leg confirms: There is not additional MPS stimulus from 40g vs. 20g of whey (much contrary to the insulin spike, by the way ;-).The side-finding that this in medical terms "high" amount of whey also lead to significant increases in urea production is - at least in my humble opinion not surprising. The increased ammonia production due to higher protein oxidation rates does after all have to be cleared from the body. Against the background that this process is facilitated by the urea cycle, anything but the observed increase in urea production would have been startling.
|"Confirmed: All Wheys, Not Just Hydro Whey Boost Glucose Uptake and Liver + Muscle Glycogen Supercompensation. Plus: How Can Taurine help?" | more|
"Indeed, in the current study, urea production rates , as well as plasma urea concentrations, were markedly raised with the ingestion of 40 g protein.Whether you consider this a "waste" of valuable dietary protein or not is probably a matter of your personal concept of protein nutrition.
Thus, instead of incorporation into muscle protein, the metabolic fate of excess exogenous amino acids contained in the 40WP was predominantly the oxidation or excretion as an indication that a state of amino acid excess was reached." (Selby. 2014)
If you are on the "protein worshipper" side of the devide, you will probably argue that you better "burn" protein for energy than carbs or fats, because otherwise you would have to eat less protein and more carbohydrates + fat and would "become fat". It goes without saying that this is bullshit - not to mention that anyone who is interested in performance and the sanity of his doctor. The poor guy would freak out, when he'd see the elevated AST and ALT levels the combination of "protein only" diets + intense physical exercise are going to produce.
Your doctor's mental sanity or the excited calls of his receptionist are probably not really your concern, but I would still not discard the performance and, in the long run, metabolic and psychological detriments from running on protein only. From an (bio-)energetic perspective it's the least effective of the three macronutrients and thus not exactly a suitable fuel source for high performance athletes.
- Cuthbertson, D., Smith, K., Babraj, J., Leese, G., Waddell, T., Atherton, P., ... & Rennie, M. J. (2005). Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. The FASEB journal, 19(3), 422-424.
- Koopman, R., Beelen, M., Stellingwerff, T., Pennings, B., Saris, W. H., Kies, A. K., ... & Van Loon, L. J. (2007). Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. American Journal of Physiology-Endocrinology And Metabolism, 293(3), E833-E842.
- Moore, D. R., Tang, J. E., Burd, N. A., Rerecich, T., Tarnopolsky, M. A., & Phillips, S. M. (2009a). Differential stimulation of myofibrillar and sarcoplasmic protein synthesis with protein ingestion at rest and after resistance exercise. The Journal of physiology, 587(4), 897-904.
- Moore, D. R., Robinson, M. J., Fry, J. L., Tang, J. E., Glover, E. I., Wilkinson, S. B., ... & Phillips, S. M. (2009b). Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. The American journal of clinical nutrition, 89(1), 161-168.
- van Loon, L. J., Saris, W. H., Kruijshoop, M., & Wagenmakers, A. J. (2000). Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures. The American journal of clinical nutrition, 72(1), 106-111.