Wednesday, August 13, 2014

Maximal Protein Synthesis in the Elderly: How Much Protein Does it Take? Another Study to Suggest More is Better!

Maximal protein synthesis requires protein, but how much exactly you need will depend on your age - the older you are the more PWO protein you'll need.
Scientists from the University of Auckland were fed up with the lack of information about the differential response in protein synthesis in response to the ingestion of various amounts of protein. Accordingly, Randall F. D’Souza et al. conducted a study to characterize the changes in intramuscular levels of EAAs and BCAAs and the expression of the "protein pump" p70S6K at Thr389, a marker of protein synthesis, in response to resistance exercise and graded ingestion of whey protein in older men.

As a regular SuppVersity reader you will probably already think: "Where is the actual measurement of the fractional protein synthesis?" The unfortunate answer: It's not there.
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Previous research had show that the ingestion of graded amounts of high-quality protein such as whey after resistance will maximize with "only" 20g of egg protein (Moore. 2009) or whey (Witard. 2014) in young men. Multiple studies in older adults (>60 years), on the other hand, suggest that they exhibit a lower anabolic signaling and MPS response to protein feeding, resistance exercise, and the combination of feeding and exercise when compared to young men (Cuthbertson. 2005; Fry. 2011; Burd. 2013). Scientists call this phenomenon age-related "anabolic resistance" (Yang. 2012b).
Figure 1: In contrast to the fractional protein synthesis in the elderly, which increases with increasing amounts of protein, the FSR of young men shows a ceiling effect at 20g+ whey protein (Yang. 2012a; Moore. 2009)
As you can see in Figure 1 from a 2012 study by Yang, the same 20g of extra-whey (total dose 40g) that was useless in young men, lead to a significant increase in protein anabolism in elderly men. Compared to young men, the MPS response to feeding 40 g of protein was yet still slightly lower in older vs. count men (Yang. 2012a; Churchward Venne. 2013b).

What is particularly relevant for the study at hand, and the previously criticized absence of actual MPS measurements is the fact that deficits in feeding induced p70S6K phosphorylation may at least partially underpin anabolic resistance in aged skeletal muscle (Cuthbertson. 2005), which is why measuring the p70S6K phosphorylation in older human subjects (mean age 71 years) in response to the graded ingestion of whey protein after a leg workout consisting of three sets of 8–10 repetitions of bilateral barbell smith rack squat, 45°leg press, and seated knee extensions at 80% of the subjects' predetermined 1R is not as irrelevant at it may initially have seemed.

Workout + supplements, that's the "whey to go" ;-)

The exercises were performed in a circuit manner with 1 min rest between each exercise and 3 min rest between subsequent sets, the exercise protocol took approximately 20 min to complete. Following completion of the exercise protocol, subjects were immediately provided with a fixed-volume (350 mL) beverage, containing a flavored noncaloric placebo, or oneof the four doses of whey protein concentrate (10 g, 20 g, 30 g, or 40 g).
Figure 2: Intramuscular amino acids. This figure is a heat map which shows groups means fold changes from the resting fasted condition. Green represents a decrease in amino acid content, white represents no change, and red represents an increase in amino acid content (D’Souza. 2014)
Subjects were instructed to ingest the beverage within 2 min and were required to ingest the total volume provided. Following consumption of the supplements, subjects rested in a supine position throughout the 4 h of post-exercise recovery with additional muscle biopsy samples collected at 2 and 4 h post exercise.
Figure 3: Higher protein intake = higher increase in p70S6K phosphorylation (left graph). This increase is linearly associated with intramuscular leucine levels (right graph | both from D’Souza. 2014)
As you can see in Figure 3, there was a similar dose-dependent increase in p70S6K as it was observed previously for MPS in skeletal muscle of elderly subjects by Yang et al. (2012b). In fact, the fold change in the phosphorylation of p70S6K (Thr389) at 2 h post exercise was correlated with the dose of whey protein consumed (r =0.51,P<001) and was found to be significantly correlated with intramuscular leucine content (r =0.32,P=0.026).

Moreover, the intramuscular BCAAs, and leucine in particular, appear to be important regulators of anabolic signaling in aged human muscle during post-exercise recovery via reversal of exercise-induced declines in intramuscular BCAAs.
Suggested Read: "Protein Timing Does Matter! Yet Only in Trained Men. More Than 2x Higher Relative Protein Retention W/ Immediate vs. 6h Post Whey Consumption in Bodybuilders vs. Rookies" | read more.
Bottom line: In the absence of a young control group and actual muscle protein synthesis (MPS) measurement, the study at hand cannot finally answer the question, whether older men require higher amounts of protein than young ones to achieve maximal increases in post-workout protein synthesis, but it is at least another piece of evidence that "more helps more" - at least in the elderly.

As mentioned in other recent posts, there are yet still many confounding variables that would have to be controlled and modified as well to answer the important (?) question: "How much protein does it take to achieve maximal post-workout protein synthesis?" Which confounding factors that would be? Well, what about the training experience? The baseline muscle mass? The protein content of the diet? And so on and so forth || Comment on Facebook!
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