Adding leucine to your post workout shake can increase muscle growth

Adding leucine to your post workout shake can increase muscle growth

Adding leucine to your post workout shake can increase muscle growth


Many people will utilise a whey protein or carbohydrate shake after their training sessions to restore muscle glycogen and to boost protein synthesis and muscle tissue repair. A great many will by now be aware that combining these two together in one shake is superior compared to either alone and this is one reason why the majority of post-workout recovery shakes are a blend of carbohydrates and protein rather than alone. Most favoured of all is a combination of a whey protein shake with fast digesting carbohydrates and this pretty much represents the default post-workout shake for athletes and bodybuilders alike.

We have previously looked at the benefits of amino acid supplementation even in the presence of a high protein diet where a glutamine and BCAA combination was shown to be beneficial for athletes engaged in training for increasing recovery and muscle mass. It is speculated that it is the branched chain amino acid Leucine which is primarily responsible for the additional muscle gains and reduction in soreness commonly noted with BCAA supplements. Could Leucine by itself offer something above and beyond what whey protein can?

A study (1) was initiated to investigate whether or not adding leucine to a carb/protein recovery shake would provide any further benefit above and beyond a carbohydrate drink and a carbohydrate and whey protein mix.  Eight male subjects, without a prior history of weight training were randomly assigned to three trials where they consumed either carbohydrate (CHO), a carbohydrate/protein mix (CHO+PRO) or a carb/protein mix augmented by free leucine (CHO+PRO+LEU) after first performing 45 minutes of resistance training.


The group consuming the mixture plus Leucine exhibited a greater insulin response and lower protein breakdown rates in conjunction with a higher rate of muscle protein synthesis. Supplying additional Leucine was also shown to result in a lower rate of protein oxidation compared to the CHO+PRO group. Protein balance, that is protein synthesis – protein breakdown, was negative during the recovery period in the CHO group while it was positive for the two trials where PRO and PRO+LEU was consumed. Protein balance was significantly greater for the CHO+PRO+LEU group compared to the CHO+PRO and CHO trials. Comparing the three groups we saw the following average values for mixed muscle fractional synthetic rate (effectively muscle protein synthesis):

CHO only – 0.061

CHO + PRO – 0.082

CHO + PRO + LEU – 0.095


The coingestion of protein and leucine stimulated muscle protein synthesis and optimized protein balance compared with the intake of carbohydrate only, with the addition of leucine being a key driver for anabolic processes.

Our Comments

The amino acid Leucine is a favourite among both bodybuilders and supplement companies alike, with a leucine arms race occurring among manufacturers to try to produce a BCAA supplement with the highest ratio of Leucine compared to the other two branched chain amino acids, Isoleucine and Valine. Although, these high ratio BCAA supplements have not been compared to traditional BCAA supplements relying on a 2:1:1 ratio, this study supports others showing that Leucine is a key driver behind elevating mTor and levels of peptide growth hormones boosting muscle protein synthesis.

The study also goes some way towards challenging the view that the body can only utilise so many essential amino acids in one serving as the subjects were provided 33.3 grams of whey protein which is considered by many to be a level at which maximal stimulation of anabolic processes would already occur. Indeed some have stated that as little as 20g of whey is sufficient with increased intakes beyond this amount being oxidized. Now, given the fact that subjects receiving the Leucine were provided a further 16 grams of Leucine, it is apparent that the traditional advice that 20-30g of whey protein is sufficient to optimise the anabolic response after a workout is false.

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1. Koopman R, Wagenmakers A, Manders R, Zorenc A, Senden J, Gorselink M, Keizer H, van Loon L (2004) Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. American Journal of Physiology: Encocrinology and Metabolism. Apr; 288 (4) E645-E653

© 2012, Reggie Johal. All rights reserved.