Leucine and the Issue with Plant-Based Proteins

by Rachel Boutagy

When it comes to protein, quality is very important and when we say quality we mean the amino acid profile that makes up the actual protein source. It has been known for some time that whey protein is a superior source of protein to turn on muscle growth and support the remodelling of muscle tissue after exercise.

Research has shown that part of the reason for whey being so effective in this regard is due to a particular high concentration of the amino acid leucine. Studies have identified that leucine directly "communicates" with signalling molecules to turn on the growth pathways. 

But not all protein is created equal when it comes to leucine content and therefore its ability to enhance muscle mass. Plant proteins in general are not particularly rich in leucine. Head to head research which has compared plant proteins to whey at the same total protein content (i.e. 20g of whey vs 20g of plant protein) have shown the superior effect of whey on muscle. Research has also identified that if you doubled the amount of plant protein (ie. 40g) the leucine content is now comparable to the 20g serve of whey which at this double dose sees a similar effect on muscle protein synthesis.


And if you think that adding leucine to your plant proteins is the solution, in one respect that is correct. Leucine added to plant protein will see a similar effect on muscle than you would expect from whey. But given that the vast majority of supplemental leucine is derived from animal hair, fur and feathers it negates one of the main reasons for being on a plant based diet.

Now its a matter of weighing up whether the additional calories and expense involved in doubling your dose, or buying additional leucine powder is worth it....