There are 8 essential amino acids we need from the diet. While dieticians, bodybuilders, athletes and their coaches squabble about daily requirements, how these amino acids are presented to muscle can be as important as how much.

Most health-conscious people are aware of the benefits of increasing the proportion of protein in their daily nutrition plan. One of the key breakthroughs in muscle physiology over the last 10 years is the affirmation that the concentration of the essential amino acids in the blood are a key regulator of muscle protein synthesis rates – inside the muscle cell.

Why is this so important?

The activation of muscle protein synthesis as the name implies, is the synthesis of new proteins – the underlying mechanism of recovery and molecular adaptations from exercise. Activating a high rate of muscle protein synthesis means more effective, efficient recovery and better adaptations from exercise and hopefully, more muscle, less body fat!

What controls muscle protein synthesis rates?

The concentration (amount) of the essential amino acids flowing around in your blood stream at any one time!

When blood amino acid levels drop, muscle protein synthesis rates decline, and so does the capacity to recover at the cellular level. Conversely, when high levels of the essential amino acids in the blood are provided (called aminoacidemia) we know this turbo-charges muscle protein synthesis rates, recovery and probably, results!

In protein research, right now maximal stimulation of muscle protein synthesis appears to be the molecular signalling name of the game.

The ingestion of 20-30grams of a high biological value protein source before or after resistance exercise appears to be sufficient to stimulate muscle protein synthesis.[1] Free form EAAs, soy, whey, caseinate, other protein hydrolysates, and even chocolate milk will do the job! [2]

However, cell signalling is one thing, achieving a higher net gain in muscle protein is the name of the muscle building game - and another matter entirely.  A higher net protein accretion or gain in muscle protein appears to require more than flooding the blood stream via a high dietary protein intake.

A higher net protein accretion or gain in muscle protein, seems to be predominantly determined by the pattern or appearance of this aminoacidemia or flood into the system.[2]

In this regard, recent work has clarified that whey proteins provide a clear advantage over other protein sources including soy (considered another fast absorbing protein) and various forms of that other milk protein, casein (hydrolyzed and unhydrolyzed)  [2,3,4]

Despite the fact, all these proteins score similarly in assessments of quality [5] their differences in absorption kinetics and impact on muscle protein metabolism go beyond simple hydrolysis and amino acid profiles.

For instance, unlike soy more of the essential amino acids from whey proteins survive splenic uptake and get to the periphery to activate a higher net muscle gain.[2]

Whey proteins (hydrolysates and isolates) appear to be the most extensively researched for pre and post resistance exercise supplementation. Possibly because of their higher EAA and leucine content [6,7] solubility and optimal digestion kinetics, [8,9] as well as the ability to create "the right flood" or concentration of amino acids in the blood [3,4] that ensures a higher net protein gain in muscle. This is in direct comparison to other protein choices. [2,8,9]

Based on this new information, it might be tempting to recommend one particular type of protein as best. However,  a more important frontier in performance nutrition (to me at least) would be the structuring of meal patterns and plans that not only create high levels of essential amino acids in circulation but also provide the combination of protein sources that ensure the greatest net protein gain from each feeding.

There is the possibility of protein metabolism differences between the sexes [10,11]. Additionally we know that some populations (older vs younger adults) tend to absorb and assimilate various protein sources differently [3,8,9]. Therefore, it may prove difficult to provide definitive answers to this question over the next decade of research.

Nevertheless, the words of one of our greatest ever protein scientist, the late Professor Peter Reeds, ring in my ears “since we know so little about the functions of various amino acids at both the mechanistic and quantitative level, to make restrictive recommendations on protein intakes for healthy and ill people would appear to be intellectually unsatisfactory." [12]

Metabolic Precision gives personal trainers & their clients many clear advantages. One is a cutting-edge approach to protein nutrition - type, timing and quantity to accelerate recovery, muscle gains and fat loss.

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1. Moore DR, Tang JE, Burd NA, Rerecich, T, Tarnopolsky, M.A., and Phillips, S.M.. Differential stimulation of myofibrillar and sarcoplasmic protein synthesis with protein ingestion at rest and after resistance exercise. J Physiol 2009 587(4): 897–904.

2. Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol 2009,107:987-92.

3. Pennings B, Koopman R, Beelen M, Senden JM, Saris WH, van Loon LJ. Exercising before protein intake allows for greater use of dietary protein-derived amino acids for de novo muscle protein synthesis in both young and elderly men. Am J Clin Nutr 2011,93:322-31.

4. West DW, Burd NA, Coffey VG, et al. Aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise. Am J Clin Nutr 2011,94:795-803

5. FAO/WHO/UNU. Protein and Amino Acid Requirements in Human Nutrition. WHO Technical Report Series. Geneva, Switzerland: World Health Organization, 2002.

6. Wilkinson SB, Tarnopolsky MA, Macdonald MJ, Macdonald JR, Armstrong D, Phillips SM. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. Am J Clin Nutr 2007, 85:1031-1040.

7. Hartman JW, Tang JE, Wilkinson SB, et al. Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters. Am J Clin Nutr 2007, 86:373-381.

8. Burd NA, Yang Y, Moore DR, Tang JE, Tarnopolsky MA, Phillips SM. Greater stimulation of myofibrillar protein synthesis with ingestion of whey protein isolate v. micellar casein at rest and after resistance exercise in elderly men. Br J Nutr 2012 Jan 31:1-5.

9. Pennings B, Boirie Y, Senden JM, Gijsen AP, Kuipers H, van Loon LJ. Whey protein stimulates postprandial muscle protein accretion more effectively than do casein and casein hydrolysate in older men. Am J Clin Nutr 2011,93:997-1005.

10. Sprint exercise enhances skeletal muscle p70S6k phosphorylation and more so in females than in males. Esbjörnsson M, Rundqvist HC, Mascher H, Osterlund T, Rooyackers O, Blomstrand E, Jansson E. Acta Physiol (Oxf). 2011 Dec 26.

11. Reduction in plasma leucine after sprint exercise is greater in males than in females. Esbjörnsson M, Rooyackers O, Norman B, Rundqvist HC, Nowak J, Bülow J, Simonsen L, Jansson E. Scand J Med Sci Sports. 2012 Jun;22(3):399-409.

12. Reeds PJ, Biolo G. Non-protein roles of amino acids: an emerging aspect of nutrient requirements. Curr Opin Clin Nutr Metab Care. 2002 Jan;5(1

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