Never(!) Sip Your Whey, If You Want to Kickstart Protein Synthesis. Over 60% Reduction in 1-5h Post Workout Protein Synthesis if You "Pulse" Your PWO Shake.

Image 1: The whey isolate used in the study - I guess as a scientists you just take whatever you get sponsored ;-) All jokes aside, any other whey isolate will do just as fine.

We all know, leucine is the magic amino acid that tells your muscles to ramp up protein synthesis. We also know that whey protein, which is made from the globular proteins the manufacturers isolate from the milky by-product of cheese production, is "the whey to go" if you do not want to ingest your leucine as a free-form amino acid or as part of a BCAA or EAA free-form amino acid blend. After all, whey is not only particularly rich in leucine (~14-15%), but also highly digestible. Well, at least this is what you are told to believe by the supplement industry... but how do we know that it is really the "speed" that makes a difference? After all, in all existing studies which compare whey to "slow digesting" proteins the absorption speed is not the only independent variable. Moreover, a recent study by Reitelseder et al. on the effects of post-exercise supplementation with 0.2g/kg body weight whey vs. casein could not find significant differences in the post-exercise protein synthetic response - and that despite the fact that whey is faster digested and does contain ~5% more leucine (Reitelseder. 2011).

A cleverly designed experiment that was (how else could it be ;-) conducted by Stuart Phillips' Exercise Metabolism Research Group at the Department of Kinesiology and Neurology at McMasters University in Hamilton, Canada, could hold the answer to the question, whether the speed with which the amino acids from your post-workout protein shake hit your body actually matters (West. 2011). Instead of using caserin or another slow-digesting protein source as control, Daniel W.D. West and his colleagues effectively eliminated all other possibly interfering variables, such as the exact amino acid composition, the carbohydrate and fat or vitamin and mineral content of the control beverage, by simply comparing the protein synthetic response to strength training (8 sets of 8-10 reps at 10RM on the bilateral leg extension machine) in 8 healthy men after bolus or pulsed (10x2.5g every 20min) ingestion of 25g of whey protein.

Figure 1: Mean serum blood concentration  (nmol/ml) of essential amino acids after bolus (red) or pulsed (blue) ingestion of 25g whey protein; * significantly (p<0.05) greater than pulse, # significantly (p<0.05) greater than bolus (data adapted from West. 2011)

While, obviously, the areas under the curve were identical for both the total essential amino acid (EAA), as well as the leucine serum levels in both groups, only the bolus ingestion of 25g of whey protein caused a significant spike (+122% over baseline, +45% over pulse) of total EAA and leucine levels about 60min post ingestion (cf. figure 1, the graph for leucine looks virtually identical). Conversely, there was a transient increase (+66% over baseline, +33% over bolus ingestion) in both serum EAA and leucine content 180min at the end of the pulsed ingestion.

Figure 2: Relative increases in mTOR phosphorylation (left) and myofibrillar fractional muscle protein synthesis rates (right) over fasted baseline after bolus or pulsed ingestion of 25g of whey protein (data adapted from West. 2011)

As the relative increases in myofibrillar fractional muscle protein synthesis rates (FSR over fasted baseline) in figure 2 (right) go to show, the spike and not the total amount of EAA/leucine over a given time period (as measured by the area under the curve) is what kicks the muscle protein synthetic machinery into gear. Even with the lower serum EAA levels at the ~3h (=180min) mark, both protein synthesis as well as mTOR-phosphorylation (figure 2, left) were still higher in the group who consumed their 25g of whey in a single bolus. So, even if your whey tastes so good that you feel like it would be a sheer waste to gulp it down all at once, you better ignore those moral objections if you want to make the most of your post-workout nutrition ;-)

Exercise the one and only "nutrient partitioner"

These results are obviously important, in that they substantiate the current practice of "getting your fast digested protein in right after exercise", what I personally did yet find even more revealing is the following remark that can be found in the extensive discussion of the results:

An intriguing and important divergence between our findings and reports in which aminoacidemia resulted in only a transient rise in MPS with infusion of amino acids or with amino acid consumption is that our results were postexercise. It appears that a unique aspect of resistance exercise is to selectively sustain elevated synthetic rates of myofibrillar proteins after protein consumption. In contrast to the effects of protein consumption alone at rest, the current results and our earlier work showed that the highest rates of MPS were observed at 3–5 h postexercise when aminoacidemia had subsided.

So, what am I preaching in each and every post? There is only one "nutrient repartitioner" which works: EXERCISE. Now, get your ass to the gym and save the money the supp companies want you to spent on dubious supplements which - even if they worked - don't give you any advantage over what you can accomplish with exercise alone for a container full of tasty whey protein isolate (which ought to be ingested in bolus portions of 25g, of course ;-).