Today I was working out at a different gym then my normal one due to travel. Between songs on my playlist I overheard two older trainers talking and giving advice to a much younger lifter on the amount of protein he should consume to see the quickest results. The two elder gentlemen were both adamant that the more protein the better, advising the client to “take two scoops” and “eat double meat” at every meal. These quotes didn’t really bother me but then I heard the line that made my blood boil. “Your body can only absorb 30-40grams of protein per meal anyways, so eat as much as you want, the rest your body will get rid of.” Obviously the tail end of that quote I have changed from the original. I have heard some variation of this quote from almost every beginner to intermediate lifter in my life, and before knowing the science it never made sense to me but now I can actual back up my claims and give advice to lifters on the proper amount of protein to consume.
Every form of protein is made up of amino acids, these nitrate binding molecules are what trigger an anabolic response. The anabolic response I will be referring to throughout this article is muscular protein synthesis, or the trigger your body needs in order to turn on the mechanisms for muscle growth. Think of it like this, lifting weight breaks down your muscle, protein, and more specifically amino acids, are the light switch that build up your muscle. Out of the twenty amino acids that make up protein, branched-chain-amino-acids or bcaa’s have the highest anabolic effect. As mentioned in my amino spiking article, the bcaa’s are (leucine, iso-leucine, and valine). Out of these three bcaa’s, leucine is the most important, and is responsible for triggering protein synthesis.
Dr. Layne Norton, and many other scientists have concluded that for the vast majority of the population anywhere from 2-3grams of leucine per meal will trigger protein synthesis. This 2-3gram range will cover anyone from an untrained 100lb woman to a 240lb muscular male. It is important to note two things, firstly we all metabolize protein different and these guidelines are just that, guidelines. Secondly, the relationship between leucine consumed and protein synthesis is not a linear one. The relationship follows more of a bell curved formation.
As the amount of leucine increases so does the amount of protein synthesis up to a certain point, at that point the maximal amount of protein synthesis will occur and any excess leucine consumed will not increase the amount of protein synthesis any further. That being said, this excess leucine will not go to waste. If the body does not need it for tissue formation or repair, it will go through a process known as gluconeogenisis and will be turned into glucose for energy. We as humans would not survive evolution to this point if we wasted excess protein, or any micro/macronutrient for that matter.
Since every protein source consumed has a different percentage of leucine within it, we would need to consume a different amount of each protein to obtain the proper amounts for optimal protein synthesis. The table below illustrates the amount of protein source you would need to consume to reach the upper limit of maximal protein synthesis at 3g of leucine. The protein amount is in grams and the column “amount of food” refers to the total amount of that protein source you would need to consume to hit that protein amount. Again these are estimates and depend on exactly what specific protein you are consuming. 
This table can be a good reference for individuals looking to cut weight as well as pack on some pounds. To initiate the same amount of protein synthesis you could either consume 120-130calories of whey protein isolate in a shake with water, or 4 cups of skim milk that would equate to 320calories. Compare this again to six large eggs at 420calories and you can begin to form a nutrition plan that fits your needs while providing as many anabolic meals as possible. Another option is supplementing with bcaa powders between or with meals to maximize protein synthesis but in my opinion, not enough research has been conducted to know for sure if this is optimal. I prefer full amino acid profiles then just branch chains. If you have any further questions to concerns feel free to drop me an email at mvolpe@spartanfitness.ca.
Contributed by Matt Volpe, Canfitpro Certified Trainer and Sales Associate at Spartan Fitness Mississauga.
References:
https://www.biolayne.com/wp-content/uploads/publications/Norton-J-Ag-Food-Ind-Hi-Tech-2008.pdf
Anthony, JC, Anthony TG, Kimball SR, Vary TC, Jefferson LS. "Orally Administered Leucine Stimulates Protein Synthesis in Skeletal Muscle of Postabsorptive Rats in Association with Increased EIF4F Formation." J Nutr 139.45 (2000)
T. Brock Symons, Ph.D., Post-Doctoral Fellow, Melinda Sheffield-Moore, Ph.D., Associate Professor, Robert R. Wolfe, Ph.D., Professor, and Douglas Paddon-Jones, Ph.D., Associate Professor “Moderating the portion size of a protein-rich meal improves anabolic efficiency in young and elderly” J Am Diet Assoc. 2009 Sept 1; 109(9): 1582-1586
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3197704/
http://www.muscleforlife.com/the-truth-about-protein-absorption-how-often-you-should-eat-protein-to-build-muscle/
http://www.precisionnutrition.com/protein-limit
http://www.nutritionexpress.com/article+index/protein/showarticle.aspx?id=807