L-Leucine – Maximizing The Anabolic Response

guy lifting weight plateL-leucine is an amino acid, and more specifically it is one of the three branched chain amino acids. The three branched chain amino acids are l-leucine, l-valine, and l-isoleucine. L-leucine is arguably the most important of these three in terms of building muscle. Research has shown that l-leucine is an important regulator of protein synthesis. (1) This essentially means that l-leucine signals both a reduction in muscle breakdown and an increase in muscle synthesis.

L-leucine is often taken around workouts to improve recovery from hard training and enhance gains in size and strength. L-leucine is also often used by bodybuilders while in the pre-contest dieting phase to reduce muscle breakdown, resulting in less muscle lost while cutting body fat to very low levels. In this article we will explore the most effective way to use l-leucine to enhance gains in size and strength.

Research has shown that the most important time to take l-leucine is around workouts, especially during and after a training session. (2) This is when consumption of branched chain amino acids, especially l-leucine, is at its highest. If l-leucine and the other branched chain amino acids are not provided during this time, the body will break down its own muscle tissue to get them to burn as energy!

But why can’t we just consume whey protein post workout to provide enough l-leucine to trigger the anabolic response? The amino acid profile of most proteins including whey contains plenty of l-leucine to keep anabolism high throughout the day, given that a person is consuming ample protein every 2-4 hours. The l-leucine bonded in proteins is slowly absorbed over a period of hours, which is great for any time other than during and post workout. During this time, we want to get the level of l-leuceine in the blood up very quickly, or “spike” the blood level of l-leucine to take full advantage of its muscle building capabilities.

This is where supplemental l-leucine comes in. Most intra-workout drinks include l-leucine, but many do not include enough at recommended doses. I recommend 5-10 grams during a workout, and 5-10 grams again post workout . Including the other branched chain amino acids along with glutamine will further enhance the muscle building effect of l-leucine. One good option is to start with an intra-workout product including branched chain amino acids and glutamine, and then add to that extra l-leucine to achieve the 5-10 gram dosages. This mixture should be consumed once during training(slowly sipped), and once immediately post training, followed by a meal about 30 minutes later.

L-leucine is certainly not a miracle supplement, but it is very useful for hard training athletes who are looking to get the most from their training. Unlike many other supplements on the market today, it has solid scientific research supporting its benefits. Adding l-leucine as a staple in your routine just could prove to be a very good investment if building muscle through intense training is your goal.


1. Anthony JC, Reiter AK, Anthony TG, Crozier SJ, Lang CH, MacLean DA, Kimball SR, & Jefferson LS. (2002). Orally administered leucine enhances protein synthesis in skeletal muscle of diabetic rats in the absence of increases in 4E-BP1 or S6K1 phosphorylation. Diabetes. 51(4), 928-36.

2. Norton LE, & Layman DK. (2006). Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. The Journal of Nutrition. 136(2), 533S-537S.


ABOUT THE AUTHOR: Cassie is a chemistry major and national level bodybuilder. Questions or comments? Talk to Cassie on theFORUMor on FACEBOOK.

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