The Magic Muscle Building Amino: Leucine

(A late Christmas present for the eyes?  Yes!)

Leucine is one of the three branched chain amino acids.  It is a building block of many of the proteins in the human body.  It is considered very hydrophobic(meaning it “fears” water), and does not like to dissolve very much at all in water.


Pictured: Leucine

Leucine turns out to be one of the(if not THE) main signalers for protein synthesis in humans.  It stimulates an upregulation in mTOR and other markers that have been linked to increased protein synthesis.  Recent research by the natural bodybuilder Layne Norton and his partner suggests that leucine is a primary regulator of initiation of protein synthesis in skeletal muscle after exercise.

Now leucine can’t exert its effects without the presence of some insulin.  Research suggests that leucine, when ingested with carbohydrates, stimulates insulin secretion that is above what carbohydrates would accomplish by themselves.  There is what is called a “synergy” between glucose and leucine.  Leucine almost DOUBLED the insulin secretion achieved by glucose.  As you probably know, insulin is a very anabolic hormone, meaning it will pack  slabs of muscle onto your frame, if you understand how to manage it correctly.  Since they also activate protein synthesis through different pathways, this is huge.  Having both present at the same time, both stimulating protein synthesis, with leucine attenuating the release of insulin from glucose ingestion is literally your key to being huge.

An interesting sidenote:  there is such a thing called leucine resistance.  It happens mostly in the elderly, when an amount of leucine sufficient to stimulate protein synthesis is no longer enough, and one must ingest more leucine to stimulate the same amount of protein synthesis they achieved when they were younger.  This means this supplement becomes even more important as you age.

OK, OK, enough with the research.  Now the goodies:

Leucine can be added to any meal, as it is a very cheap amino acid to buy.  And yes, it will exert it’s effects for you on every meal, if that is in your game plan.  Five grams seems to be the amount needed for a person of larger size to stimulate protein synthesis in the skeletal muscle.  Now it can be inconvenient to remember to take leucine all the time, so if you don’t want to think about it too hard, just take it with your post workout shake/carbs, and if you have some sort of pre-workout stimulant, toss it in there too.  It will help stave off the catabolism that can occur when training sessions last a long time.

So there you have it: Leucine, the wonder amino.  I appreciate any comments, or additions you have.

Stipanuk, Martha H. Leucine and protein synthesis: mTOR and beyond. Nutrition Reviews. 2007;Mar;Vol. 65, No. 3:122-9.

Padden-Jones D, et al. Amino acid ingestion improves muscle protein synthesis in the young and elderly. Am J Physiol Endocrinol Metab. 2004 Mar;286(3):E321-8.

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

Rieu, Isabelle. Leucine supplementation improves muscle protein synthesis in elderly men independently of hyperaminoacidaemia. J. Physiol. 2006;575;305-15.

Dionysia Kalogeropoulou, Leucine, when ingested with glucose, synergistically stimulates insulin secretion and lowers blood glucose Metabolism Clinical and Experimental 57 (2008) 1747–1752

Norton LE and Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 2006; 136(2):533S-537S.

Jeffrey S. Greiwe, Guim Kwon, Michael L. McDaniel, and Clay F. Semenkovich, Leucine and insulin activate p70 S6 kinase through different pathways in human skeletal muscle, Am J Physiol Endocrinol Metab 281: E466-E471, 2001

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2 Responses to The Magic Muscle Building Amino: Leucine

  1. Nick says:

    Hey thanks for the article. One gripe. You tell us what NOT to buy, how about name dropping a few GOOD supplements. I looked up Leucine at and there are dozens of products. Which is best?

    • Brandon says:

      Ive used bulk leucine from nutraplanet with success. If you wanted a good supplement to take look into the regenyx in our BOI store. It has whey ISO, carbs, and leucine. So you get the glucose to cause the insulin release as discussed in this article along with a decent dose of leucine for pwo nutrition.

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