What Is Leucine? And Why Should You Care?

Protein molecules are made up of individual building blocks called amino acids.  A cheesy (and oversimplified) analogy for understanding this concept is to think of a fully assembled Star Wars X-Wing Lego set as a protein molecule, and the individual Lego blocks that it’s built with would be the amino acids. 

There are 20 amino acids, and leucine is quite possibly the most important one to get in your diet.  Here is why: 

1. Leucine Stimulates Muscle Protein Synthesis 

Muscle protein synthesis is the building and repair of muscle tissue. Getting our bodies to do this is essential if we want to put on muscle mass.  But anyone who engages in physical exercise will experience the breakdown of tissue, and as a result, we all need muscle protein synthesis.  Without it we will inevitably experience the loss of skeletal muscle mass (called sarcopenia) over time. 

Leucine is important because it provides the greatest stimulus for muscle protein synthesis of any amino acid.¹ 

2. It’s an Essential Amino Acid 

When discussing nutrition, the term “essential” does not mean “important.”  It means that it must be gained through nutrition (aka we have to eat it because our bodies can’t produce it).  Of the 20 amino acids, 9 are essential.  And leucine is one of those 9. 

Because leucine is critical for muscle protein synthesis, and because our bodies can’t produce it, it’s crucial to consume sufficient amounts of dietary leucine. 

3. It’s a Branched-Chain Amino Acid 

Without going into the molecular structure of what makes an amino acid “branched-chain,” it’s important to understand why these amino acids are unique. 

In general, we don’t burn protein for energy.  Our bodies break down fats and carbs for energy, and protein is used to build stuff.  The exception to this is with the branched-chain amino acids.  Our body can actually harvest energy from these specific aminos, which is particularly helpful when a person is in a caloric deficit (aka trying to lose body fat). 

When dieting for fat loss, consuming a greater amount of these amino acids, leucine in particular, will help prevent the loss of lean mass both through the stimulation of muscle protein synthesis, as well as helping to cover the energy deficit created by one’s diet and exercise. 

To wrap up, leucine is important.  If you want to be healthy and fit, you need it.  And the only way to get it is through your diet.  You can get leucine through dietary supplements.  This is why our VIVL Nutrients Plant Protein-L has the highest leucine content of any plant-based protein. But some good dietary sources of leucine are wild-caught salmon, grass-fed beef, and cage-free eggs. 

1.  Atherton PJ, Smith K, Etheridge T, Rankin D, Rennie MJ. Amino Acids. 2010;38:1533–1539.