Over the past several decades there have been amazing gains in our understanding of how muscle responds to exercise and nutrition. Basically we know resistance exercise increases the processes that build protein in muscle and in turn builds muscle strength and size.(1) However, this only leads to optimal improvements over time if there is adequate daily protein intake around the training time as well as throughout the day and exceeding 2X the RDA.(2) The results of some university studies suggest consuming protein increases muscle protein production (muscle protein synthesis or MPS) in a relative fashion, it becomes “statistically greater” at around 20 grams of high quality protein, and 40g might not yield additional MPS benefit.(3,4) In addition, the pattern of entry of amino acids into the blood have led some to speculate there is a progressive reduction in protein digestion and absorption with higher meal protein levels. Both concepts have led some to espouse that any protein consumed above studied levels (e.g. 20-30 grams) is not beneficial or worse yet, not even absorbed and is therefore wasted. This line of thinking is nonsensical and completely inaccurate.
Here’s why:
First things first - digestion and absorption. Whether you consume 20, 30 or even 50 grams of protein there is no on/off switch for digestion and absorption, both of which remain highly efficient. However, a larger intake of protein-based food can increase the amount of content moving from the stomach to the small intestine per minute (it should still take longer for all of it to get there).(5) The minute-by-minute benefit can be augmented to some degree, and so too can the benefit be extended in a relative fashion. This is most obvious with whey protein powders, as the level of certain amino acids in the blood can be higher earlier and remain higher later when ingesting 40 grams as compared to 20 grams.6 Secondly, numerous factors influence the rate and quantity of amino acids in the blood including composition and size of meal, type and level of protein and nutrition state.(7) Third, more of the protein-derived amino acids resulting from a higher intake might be destined for other tissue, which can thus influence blood amino acid levels.(8) Protein intake is not as simple as eating a certain level of protein and looking for the amino acids in the blood.
It is important we don’t view potential protein benefits through the narrow lens of MPS. If so, we would need to keep in mind 1) protein is found throughout the body and a relationship exists between muscle and non-muscle protein metabolism, 2) muscle protein balance is based on muscle protein synthesis and breakdown, 3) protein response varies person to person and especially in older individuals and 4) we are still limited in research information. For instance, while earlier studies suggested that 20 grams of high quality protein could maximally stimulate MPS in younger males,(3,4) newer research suggests 40 grams of whey protein increases MPS significantly higher than 20 grams.(6) One of the key differences in these studies might be the training itself, with the higher intake being more beneficial with whole body training versus isolated extremities.(6) Another important factor is age; older individuals seem to have a need for more protein to get an equivalent MPS response to food protein, with and without training.(9-11) Further still, higher levels of protein may continue to lower total body protein breakdown even after MPS has plateaued.(12) And let’s not forget that when people restrict calories to reduce body weight, more protein daily supports a better outcome.(13)
Now how about the math? If we only set protein recommendation at levels that stimulate MPS (e.g. 20 - 25 g) we need we may not achieve the appropriate daily intake levels recognized to yield better results over time. Let’s consider the needs of a 190lb male (86 kg) who trains at the gym to build muscle and following guidelines of research suggesting a daily intake of at least 1.75g per kg is more beneficial then less.(2) Our male would want to get above 170 grams daily and shooting for only 25 grams would only get him 60% to his daily goal.
Finally, protein has numerous benefits beyond building muscle. Compared to carbs and dietary fat, protein suppresses hunger to a substantially greater extent than other macronutrients.(13) Also, protein is more thermogenic meaning it raises metabolism more than equivalent intakes from carbohydrate and fat.(14) Further still, for people trying to lose weight, increasing protein in the diet and performing resistance exercise is clearly the way to go.(15-17) Taken together, more calories from protein in a diet would support most personal goals for weight, fitness, performance with several potential benefits and no waste.
References
Phillips SM. A brief review of critical processes in exercise-induced muscular hypertrophy. Sports Med (2014): 44 (1): S71-S77.
Schoenfeld BJ, Aragon AA, Krieger JW. The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. J Int Soc Sports Nutr. 2013 Dec 3;10(1):53.
Witard OC, Jackman SR, Breen L, Smith K, Selby A, Tipton KD. Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. AJCN 2013; 99:86-95.
Moore, D. R., M. J. Robinson, J. L. Fry, J. E. Tang, E. I. Glover, S. B. Wilkinson, et al. 2009. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am. J. Clin. Nutr. 89:161– 168.
Read NW, Cammack J, Edwards C, Holgate AM, Cann PA, Brown C. Is the transit time of a meal through the small intestine related to the rate at which it leaves the stomach? Gut. 1982 Oct;23(10):824-8.
MacNaughton LS, Wardle SL,Witard OC, McGlory C, Hamilton DL, Jeromson S, Lawrence SE, Wallis GA, Tipton KD. The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein. Physiol Rep, 4 (15), 2016, e12893.
Macdonald IA. Physiological regulation of gastric emptying and glucose absorption. Diabet Med. 1996 Sep;13(9 Suppl 5):S11-5.
Deutz NE, Ten Have GA, Soeters PB, Moughan PJ. Increased intestinal amino-acid retention from the addition of carbohydrates to a meal. Clin Nutr. 1995 Dec;14(6):354-64.
Murphy CH, Oikawa SY, Phillips SM. Dietary Protein to Maintain Muscle Mass in Aging: A Case for Per-meal Protein Recommendations. J Frailty Aging. 2016;5(1):49-58.
Baum JI, Kim IY, Wolfe RR. Protein Consumption and the Elderly: What Is the Optimal Level of Intake? Nutrients. 2016 Jun 8;8(6). pii: E359.
Kim I.-Y., Schutzler S., Schrader A., Spencer H., Kortebein P., Deutz N.E.P., Wolfe R.R., Ferrando A.A. Quantity of dietary protein intake, but not pattern of intake, affects net protein balance primarily through differences in protein synthesis in older adults. Am. J. Physiol. Endocrinol. Metab. 2015;308:21–28.
Kim I.-Y., Schutzler S., Schrader A., Spencer H.J., Azhar G., Ferrando A.A., Wolfe R.R. The anabolic response to a meal containing different amounts of protein is not limited by the maximal stimulation of protein synthesis in healthy young adults. Am. J. Physiol. Endocrinol. Metab. 2016;310:73–80.
Bendtsen LQ, Lorenzen JK, Bendsen NT, Rasmussen C, Astrup A. Effect of dairy proteins on appetite, energy expenditure, body weight, and composition: a review of the evidence from controlled clinical trials. Adv Nutr. 2013 Jul 1;4(4):418-38.
Acheson KJ, Blondel-Lubrano A, Oguey-Araymon S, Beaumont M, Emady-Azar S, Ammon-Zufferey C, Monnard I, Pinaud S, Nielsen-Moennoz C, Bovetto L.Protein choices targeting thermogenesis and metabolism. Am J Clin Nutr. 2011 Mar;93(3):525-34.
Josse AR, Atkinson SA, Tarnopolsky MA, Phillips SM. Increased consumption of dairy foods and protein during diet- and exercise-induced weight loss promotes fat mass loss and lean mass gain in overweight and obese premenopausal women. J Nutr. 2011 Sep;141(9):1626-34
Arciero PJ, Edmonds RC, Bunsawat K, Gentile CL, Ketcham C, Darin C, Renna M, Zheng Q, Zhang JZ, Ormsbee MJ. Protein-Pacing from Food or Supplementation Improves Physical Performance in Overweight Men and Women: The PRISE 2 Study. Nutrients. 2016 May 11;8(5). pii: E288.
Arciero PJ, Edmonds R, He F, Ward E, Gumpricht E, Mohr A, Ormsbee MJ, Astrup A. Protein-Pacing Caloric-Restriction Enhances Body Composition Similarly in Obese Men and Women during Weight Loss and Sustains Efficacy during Long-Term Weight Maintenance. Nutrients. 2016 Jul 30;8(8) pii: E476.
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