Thursday, February 5, 2009

Research Review: Do You Only Need 20 Grams of Protein Post Workout?

Today I have a special treat for the reader's of this blog. A new research study was published recently looking at the effect of only 20 grams of protein and its affect on protein synthesis (increasing muscle).

Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men.

(full abstract below)

I sent the study off to my buddy Carl Lanore of Super Human radio and he did a great interview with Dr. Stuart Phillips, one of the researchers on the study. You can see the abstract below and also listen to the whole show below here too. Click HERE for the show and the interview. Be sure to check out the show on an almost daily basis as Carl does an amazing job and it is a FREE resource to you!

I also asked Georgie Fear if she would be kind enough to write up a short review from her point of view. She is a Registered Dietitian, Personal Trainer, and Kettlebell Instructor (go KBs!!!), an active member at the Precision Nutrition forum and a PhD Candidate in nutrition. In addition, she is an athlete and practices what she preaches.

Be sure to check out her blog HERE and I have also linked it on the right hand side.

So, without further ramblings, here are her thoughts on the study.

Study Review by Gerogie Fear, RD, CPT
Interesting results:
Insulin was greater with more protein.
Blood glucose remained similar between groups.
Protein synthesis of muscle proteins and albumin increased up to 20 g protein, but not any more with 40 g.
No increased phosphorylation of S6K, rps6, or EIF2b.
Leucine oxidation increased with 20 and 40 grams.
No measurements of protein breakdown.
No measurements of non-phosphorylated proteins.

The authors attempt an interesting study but fail to use all the methods needed to make their argument. It appears that the main goal of this work was to determine if protein intake can result in more muscle mass. (And, Mike, I'd assume that's why you'd be interested in sharing its content with readers.) But muscle protein synthesis is only half of the equation, without assaying muscle protein degradation you cannot even guess whether the total amount of muscle protein would change - either short term or long term.

This study doesn't even look at protein degradation. Increased muscle protein synthesis, as shown in this paper, may simply reflect increased turnover - i.e. proteins are being degraded and rebuilt at the same time. It is well documented that muscle protein is constantly undergoing remodeling and turnover. Especially after hard exercise, which damages muscle fibers, a burst of remodeling activity would be expected. It has been shown that even in the absence of exercise that eating protein induces protein turnover, but not necessarily a net protein gain.

One problem these authors face is that they report an increase in protein synthesis without an increase in phosphorylation of S6K, rps6 or EIF2b. (These proteins are regulatory elements in the protein synthesic machinery, controlled by mTOR). This is equivalent to saying a house is being built, but we don't see any tractors, or hammers, or construction workers at the site. Hmmmmmmmm is all I can say.

When measuring protein phosphorylation statues, as in this experiment, it is customary to immunoblot for both the phosphorylated and non-phosphorylated amunts of protein, which was not done. They simply measured how much was phosphorylated and got on with it. Considering that their findings do not agree with the literature (Insulin increases activity in the mTOR pathway- and they have an increase in insulin) they should have done a secondary blot for the nonphosphorylated forms. It is possible that their methods weren’t perfect, and the phosphorylation state wasn’t preserved. (Blotting for fragile phosphoproteins isn’t easy!) The proteins can be de-phosphorylated, so if you see no increases where you expect them (S6K, EIF2 etc), you should do it again to make sure it wasn’t a methods error.

The authors address this by saying that they “speculate” that increased amino acid availability caused more protein to be synthesized. Back to our house analogy, simply accumulating a pile of bricks at the site doesn’t cause a house to go up, with no machinery or workers to build it.

I am not saying that one can be sure their blots were not accurate. I would be interested in seeing levels of glucagon and stress hormones measured as well as insulin, because these do act somewhat in opposition. Perhaps the catabolic hormones are stimulated by the exercise, and kept the protein synthetic machinery from becoming phosphorylated? (But that’s doesn’t jibe with the increased protein synth.)

The writers claim that protein intakes above 20 g are excessive, based on the increase in leucine oxidation they observed. However, given the complete absence of carbohydrate from all groups, amino acid oxidation may be resulting from a need for energy! Why might it increase is the 20 and 40 g groups? Perhaps the other groups, given less calories and protein, oxidized more alanine and other amino acids, which were not labeled and thus couldn’t be measured. Levels of urea in the groups did not differ, so its hard to make an argument that the 20 and 40 gram groups were burning more protein because it was excessive.

Okay, so what’s the bottom line? This study provides interesting evidence that exercise followed by protein ingestion causes muscle protein activity (synthesis which may or may not be accompanied by increased breakdown). It also shows that 20 g mixed AA is enough to elicit the maximal insulin response without carbs – I found this to be the most useful part of the paper! No claims can be made based on these results (observing only 4 h) that net protein gain (more muscle mass) will be maximized by 20 g protein, as net protein accumulation is under long term regulation. Endocrine factors, resistance training protocol, and overall energy balance are far more influential in determining whether an athlete gains and maintains muscle mass. Bodybuilders aren’t made in 4 hours.

Again, insulin is important as a powerful driver of protein synthesis. To gain the greatest insulin surge, you need carbs plus amino acids. So in that respect, these athletes weren’t maxed out- adding carbs might have heightened the anabolic response to the lower AA levels, or prevented oxidation of leucine in the higher AA levels as a preferred fuel source would have been provided.

That’s why science always goes on.
---Georgie Fear

Thanks again to Georgie for the review--much appreciated!

Any comments, let me know!

Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men.

Moore DR, Robinson MJ, Fry JL, Tang JE, Glover EI, Wilkinson SB, Prior T, Tarnopolsky MA, Phillips SM. Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Canada.

BACKGROUND: The anabolic effect of resistance exercise is enhanced by the provision of dietary protein.

OBJECTIVES: We aimed to determine the ingested protein dose response of muscle (MPS) and albumin protein synthesis (APS) after resistance exercise. In addition, we measured the phosphorylation of candidate signaling proteins thought to regulate acute changes in MPS.

DESIGN: Six healthy young men reported to the laboratory on 5 separate occasions to perform an intense bout of leg-based resistance exercise. After exercise, participants consumed, in a randomized order, drinks containing 0, 5, 10, 20, or 40 g whole egg protein. Protein synthesis and whole-body leucine oxidation were measured over 4 h after exercise by a primed constant infusion of [1-(13)C]leucine.

RESULTS: MPS displayed a dose response to dietary protein ingestion and was maximally stimulated at 20 g. The phosphorylation of ribosomal protein S6 kinase (Thr(389)), ribosomal protein S6 (Ser(240/244)), and the epsilon-subunit of eukaryotic initiation factor 2B (Ser(539)) were unaffected by protein ingestion. APS increased in a dose-dependent manner and also reached a plateau at 20 g ingested protein. Leucine oxidation was significantly increased after 20 and 40 g protein were ingested.

CONCLUSIONS: Ingestion of 20 g intact protein is sufficient to maximally stimulate MPS and APS (albumin protein synthesis) after resistance exercise. Phosphorylation of candidate signaling proteins was not enhanced with any dose of protein ingested, which suggested that the stimulation of MPS after resistance exercise may be related to amino acid availability.

Finally, dietary protein consumed after exercise in excess of the rate at which it can be incorporated into tissue protein stimulates irreversible oxidation.