Saturday, February 11, 2012

Protein Synthesis Beyond the "20g Limit": Study Shows Exercise Facilitates 32% Greater Increases in Fractional Protein Synthesis With 40g Instead of 20g of Whey PWO

Image 1: Now that the nasty "20g limit" is tumbling and more is finally more again (I know how dearly some of you have been waiting for this news ;-), I do already envision the first commercial gyms offering a pool filled with delicious whey isolate for the ultimate post-workout "more is more"-experience  (img
If you, just like me, have been following the discussions of the bros and pros on the various bodybuilding and fitness related bulletin boards, all across the web, you will probably have noticed how the dietary recommendations rookies are given have changed over time. From "eat everything in sight" approach to bulking, which had something of the good old days, where John Grimek was notorious for not finding a restaurant that could do his huge appetite justice, over a "make sure you get at least 2g/lbs of protein" to the "more than 20g of whey are a waste of resources" you are confronted with, today. A cursory read of the main results of a recently published study (once more) from Stuart Phillips lab at the McMaster University (thx to Steven Arcera for the heads up on Facebook), does  yet suggest that even this latest advice, which is rooted in the believe that the ingestion of 2-3g of leucine would maximize protein synthesis, is now past its sell-by date.

40g is more than 20g? You must be kidding me!

In one of those, at least in my mind, somewhat artificial single-leg exercise studies (Yang. 2012), in which the subjects perform a given number of single legged leg extensions (in the study at hand 3 sets @10RM) Yang et al. tried to elucidate the individual and combined effects of different doses (10g, 20g, 40g) of whey protein alone or in combination with the aforementioned unilateral leg exercise on myofibrillar protein synthesis (FSR) in thirty-seven non-frail older men (~age 71 +/- 4 years, BMI 26 kg/m²).
Figure 1: Myofibrillar fractional protein synthesis in exercised and non-exercised leg of older men after 3 sets of leg extensions and the ingestion of either control beverage or 10g, 20g or 40g of whey protein (data adapted from Yang. 2012)
If you take a look at the results in figure 1, you do not have to hold a degree in exercise science, molecular biology or physics (*lol*) to conclude that for this particular group of subjects and under the given experimental conditions, the previously invoked "20g limit" does not exist. In other words, the ingestion of 20g of whey protein after a bout of resistance training does not maximize fractional protein synthesis in the myofibrillar compartment of the exercised muscles in older non-frail men. Moreover, ...
[m]yofibrillar FSR in the non-exercised leg (fed only) was significantly increased with W20 and W40 compared with W0, with no significant difference observed between W20 and W40. [...] in the W20 and W40 exercised legs, myofibrillar FSR was statistically elevated above the W0 and W10 exercised legs. Furthermore, myofibrillar FSR for W40 was approximately 32 % greater than for W20 (p < 0.02).
With the increase in FSR from 20g to 40g still being more than just marginally significant (+32%!), I would bet any money (well, sort of ;-) that we would not see significant ceiling effects with 60g of whey... maybe not even with 80g.

So what? Replace your 400ml shaker with a huge barrel to dissolve 1kg of whey post-workout?

The stark contrast to previous findings in younger individuals, as well as the overall somewhat ridicolous "exercise" protocol (I mean, 3 sets à 10 reps with one leg?) does yet raise the question how significant these results actually are. Yang et al. obviously believe that the age of the subjects may be the underlying reason for these discrepancies and state:
Given the evidence that the muscle protein synthetic response following resistance exercise is blunted in aged muscle, our data and that of others suggest that consuming a relatively high amount of dietary protein after resistance exercise may, potentially, increase rates of MPS in the elderly to the same extent as in young adults.
And while this obviously could factor in, the trainee in me tells me that you can as well walk in the park to induce the same "protein synthetic response" as with 3 sets of 10 reps (just to make sure: this is not a scientifically validated fact ;-)
Figure 2: Fractional  protein synthesis in the Moore study, where a ceiling effect occurred and the Yang study, where it was absent (data based on Moore. 2008 and Yang. 2012)
If we know look at the absolute FSR in response to real exercise, like the 4 sets of leg presses, leg curls and leg extensions, the young subjects in the 2009 study by Moore et al. (Moore. 2008), Yang and his colleagues mention in support of the 20g limit (by the way: Moore et al. used 20g of egg protein with "only 1.2g of leucine"), and the "walk in the park"-type single-legged leg extensions from the study at hand, I personally would say that it is much more likely that there is an overall physical upper limit for fractional protein synthesis. This would imply that the combined effect of the nutritional and the exercise stimulus would be rate limit, simply because the amino acid transport into the cell is limited.

We still miss lots of pieces of the puzzle and search for them in the wrong places

Personally, I feel that these results confirm my gut feeling that the current focus on a) the 2h post-workout window after a single workout, b) the signaling over the substrate function of protein ingestion and c) the narrow-minded focus on whey or even leucine, in isolation, may have helped us to elucidate the important role of mTOR & co, but are of  little to no practical relevance for the average gymrat. What, for example, happens if you co-ingest whey + casein? What is the influence of the whole foods meal, I have ~45min after my shake at the gym? What will the insulin spike (3x over baseline for the 40g whey group in the study at hand) do to my blood sugar levels (catecholamins, cortisol, glucagon, ...), if I have a "real" workout under my belt and my liver and muscle glycogen stores are depleted? These are only a few examples of questions, which are in my humble opinion of much greater importance, than the "ideal" amount of whey, let alone leucine, I am supposed to take after my workouts.