Leucine and Driving Muscle Protein Synthesis

By: Gavin Hemmerlein

Now we get to the fun part. We have covered all of the macronutrients in decent depth, but I want to start talking about the little things to focus on. Leucine is a Branch Chain Amino Acid that has very important effects and an important role in our bodies. It is believe to help with sterol development as well as potentially aiding the regulation of blood sugar and improve the brain functions as well. All of this is great for health purposes, but what I really want to talk to you about is the muscle building properties. This is what really excites a muscle head like myself.

We all know that most bodybuilders are obsessed with protein. Frankly they probably eat too much, but that’s ok as long as they have healthy kidneys to filter that. That subject, however, is for another day. What I want to discuss is how do we know HOW much protein that we truly need?

There is a lot of evidence towards leucine being the driving factor behind muscle protein synthesis (MPS). Before I get ahead of myself, I want to explain MPS a little more. When your body uses proteins to rebuild, the protein is constantly added (synthesis) to the muscles (or for generic protein synthesis it is anywhere in the body) and then discarded (degradation). Think of this like a shelf life for the muscle protein. This constant addition and subtraction is what we like to refer to as protein turnaround. The thing to note is that the body is CONSTANTLY doing both of these processes; they just occur at different rates. When synthesis occurs at a faster rate than degradation, we have an anabolic or mass building situation. When the reverse occurs (degradation is higher than synthesis) we have a catabolic or mass losing situation.

When I speak of MPS saturation I am talking about a top out rate at where the synthesis occurs. It’s at this point that if you were to eat one more amino, it would do absolutely nothing more on instigating more synthesis. It’s topped out.

There have been plenty of studies that confirm that approximately 15g of Essential Amino Acids (EAA) will saturate MPS for subjects that were between 155 and 165 lbs. [1, 2] The results of these studies resulted in a further hypothesis that it was leucine that was the initiator. When more studies were done with leucine, we found that this did occur! [3] The approximate amount of leucine for a 15g EAA intake was about 3.2g dosage. This decision was even more so supported during a 2012 study where the comparisons of whey powder and supplementation of leucine were compared. [4] While the whey sustained the stimulation for a longer timeframe, a suboptimal level of EAA (12g) was supplemented with some leucine (.75g) and it resulted in a saturation of MPS.

The next logical step would be, how long does this effect last? A couple studies have shown (and subsequently confirmed by other studies) that leucine supplementation will last for approximately 2 hours and 3 hours for a whole meal. [5, 6, 7] this is surprising considering that the bloodstream contained the amino acids for 6 hours. It was also seen that MPS appeared more readily saturated with the addition of 20g of carbs. [6] It is also postulated that continual ingestion will not help and could quite possibly lower the response. So before you muscle heads go and start eating turkey legs all day long, let’s also take a look at some studies on refractory responses or a lower in the effectiveness if you will.

Another interesting study I’d like to highlight confirmed the spreading of meals. When consuming 4 small meals a day, a study on 8 elderly women say that an evenly spaced out intake of protein compared to an intake of 80% in one meal resulted in differing results. There are some limits to this, however. Starting off, this is obviously a small sample size and it is elderly women and not athletes. The total intake of protein was only 60g. So the comparison of meals were 15-15-15-15 and 48-4-4-4 grams respectively. Those limitations are there, but I think that they can be applied to other aspects. I’d believe this would support the recommendations. [8]

There is some postulation of the idea that supplementing some free form aminos and CHO (15g EAA or 3.2g leucine and 20g CHO) between full meals might increase MPS responses as well. [9] I’m a little hesitant on this one because I’m not fully convinced of it. I simply wanted to mention it.

OK, time to take a deep breath. What does this all mean? Well it all leads up to a few simple recommendations that I’ve been giving for years:

1 – Eat your protein evenly throughout the day (five meals mean total intake is divided by five. Four meals means divide it by four). I don’t mess too much with the total daily recommendations outside of the normal governing bodies (NASM, ACE, NSCA, ISSA, etc.)

2 – Consume your BCAAs! I don’t care where you get these (plant or animal proteins), but these are needed for stimulation

3 – You can supplement leucine if you feel the need, but this isn’t crucial

4 – Eat mixed meals. This should be obvious from our Carbs convo, but let’s state it again.

5 – Stop eating every 2 hours! It doesn’t do what you want and is not necessary

That’s the most simplified version of what I recommend. It’s pretty simple and effective. Go get it.

– Gavin

If you want to email me, my email is hammerstandfitness@gmail.com – Feel free to email this address at any time!


  1. Paddon-Jones D, Sheffield-Moore M, Zhang XJ, Volpi E, Wolf SE, Aarsland A, Ferrando AA, Wolfe RR. Amino acid ingestion improves muscle protein synthesis in the young and elderly. Am J Physiol Endocrinol Metab. 2004 Mar;286(3):E321-8.
  2. Tipton KD, Ferrando AA, Phillips SM, Doyle D Jr, Wolfe RR.

Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol. 1999 Apr;276(4 Pt 1):E628-34.

  1. Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 2006 Feb;136(2):533S-537S.
  2. Churchward-Venne TA1, Burd NA, et al. Supplementation of a suboptimal protein does with leucinssential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. J Physiol. 2012 Jun 1;590(Pt 11):2751-65. doi: 10.1113/jphysiol.2012.228833. Epub 2012 Mar 25.
  3. Anthony JC, Lang CH, Crozier SJ, Anthony TG, MacLean DA, Kimball SR, Jefferson LS. Contribution of insulin to the translational control of protein synthesis in skeletal muscle by leucine. Am J Physiol Endocrinol Metab. 2002 May;282(5):E1092-101.
  4. Bohe J, Low JF, Wolfe RR, Rennie MJ. Latency and duration of stimulation of human muscle protein synthesis during continuous infusion of amino acids. J Physiol. 2001 Apr 15;532(Pt 2):575-9.
  5. Norton LE, Layman DK, Garlick PJ, Brana D, Anthony TG, Zhao L, Devkota S, Walker DA. Translational controls of skeletal muscle protein synthesis are delayed and prolonged associated with ingestion of a complete meal. 2007 Experimental Biology meeting abstracts [on CD-ROM], Abstract #694.6.
  6. Arnal MA, Mosoni L, Boirie Y, Houlier ML, Morin L, Verdier E, Ritz P, Antoine JM, Prugnaud J, Beaufrere B, Mirand PP. pulse feeding improves protein retention in elderly women. Am J Clin Nutr. 1999 Jun;69(6):1202-8.
  7. Paddon-Jones D, Sheffield-Moore M, Aarsland A, Wolfe RR, Ferrando AA. Exogenous amino acids stimulate human muscle anabolism without interfering with the response to mixed meal ingestion. Am J Physiol Endocrinol Metab. 2005 Apr;288(4):E761-7.