The Ultimate Supplement for Lean Muscle Gains – L-Leucine

By Myprotein Writer Joe Neill 
Personal Trainer
No Limits Strength and Conditioning Centre Liverpool


What is Leucine?


Leucine is a naturally occurring amino acid which forms part of a chain to produce protein molecules.Leucine

It can be found in almost all of your protein containing food sources, from eggs to spirulina and of course supplements such as Whey Protein Powder and Branch Chain Amino Acids (BCAA’s), as well as being available in single form, often given the name L-Leucine.


What do we use Leucine for?


Leucine is essential to facilitate protein synthesis. Anyone who is trying to build some sort of noticeable change in lean body mass (muscle) will require protein synthesis to achieve a change in body mass.

Maintaining a positive protein balance is vital (especially after training) in ensuring that your body doesn’t stay in a catabolic state due to training.

Exercise can be a stressful procedure for the body and can actually promote the breakdown of muscle (catabolism). So in order to negate this, it is common knowledge to consume some form of dietary protein which will aid recovery and promote growth after resistance training (weight session).




Because of the relationship between leucine, mTOR and protein synthesis (Churchward-Venne – ?2012).


The Anabolic pathway mTOR


So what do you need to know about the anabolic pathway called mTOR?

The important thing to understand is that it’s key to triggering protein synthesis.

In simple terms, mTOR is a sensor that detects when there are adequate amounts of leucine (which suggests there are adequate amounts of protein) in order to synthesise new muscle proteins, which in turn will lead to  hypertrophy (growth of muscle).

On the other hand, if there is a decreasing amount of leucine present that would suggest there is not an adequate amount of dietary protein – resulting in  mTOR  down regulating protein synthesis… Which, you guessed it –  results in no muscle gain!


Who should use Leucine?


Leucine is present in a lot of your protein sources which ensures you’re getting enough throughout your day to aid  recovery and growth.

To maximise hypertrophy it has been suggested to supplement with the amino acid in single form. In terms of a serving size, I believe it depends on yours goals, type of training and also time of day. For example:


depletion workout


Professional gym goer/bodybuilders – it certainly wouldn’t harm to add 3g of leucine powder to your  post workout shake for recovery/growth. Some studies have shown that the post workout ‘anabolic window’ (when protein synthesis is at its highest) lasts up to 48 hours, ( Churchward-Venne, TA 2012) therefore, supplementing with Leucine in this period could maximise growth.


Athletes – Performance relies on quality of practice which includes nutrition, in my opinion investing in leucine would only improve your recovery, lean body mass, strength and therefore performance.


Average gym goer – If you aren’t overly concerned about the complete maximisation of your potential, or enjoy going the gym but aren’t 100% committed to the diet, then keep drinking your whey protein drink post workout (leucine is still present) so it would be sufficient.


When to use Leucine?


If you are a fitness competitor training for a show, your priority is going to be retention of lean mass during the ‘cutting’ phase. Now lets say this person has an AM cardio session and wishes to fast (the pros/cons of fasted cardio is a debate for another day), having a 3g serving of leucine would help reduce muscle wastage by keeping protein synthesis stimulated and reducing protein breakdown.


Sergi Leucine


A similar scenario would be those committed to the Lean Gains intermittent fasting protocol (Berkhan, 2010): a fasting window that lasts on average 16 hours per day. Berkhan suggests ‘supplementing with BCAA in and around training, during the fasting period, for the reason  mentioned above, the maintenance of a positive protein balance’.





Doses of Leucine can differ depending on training schedules. However, a suggestion for a healthy adult is around 42mg/kg per day.

Some studies suggest the upper limit should be 34g per day for your average person… but it’s not uncommon for people to take more in supplement form alone.


Take home message


If you are a serious weight lifter/athlete supplementing with leucine, a single form is worth the investment –  but it is not ‘essential’ for everyone as long as you have a diet rich in protein.


Leucine for lean gains








Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.



Writer and expert

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