Leucine Content of Protein Determines Effect on Protein Synthesis

Amino acids are important for muscle growth because they serve as the building blocks for protein synthesis. The amino acid leucine is particularly important because it serves as a key chemical for turning on the mTOR biochemical pathway of protein synthesis. A University of Illinois study using rats showed that the leucine content of various food proteins was the most important factor determining the food’s effect on protein synthesis. They examined the effects of wheat, soy, egg and whey protein, which contained 6.8, 8.0, 8.8, and 8.9 percent leucine. The leucine content of foods is critical for promoting muscle protein synthesis. (Nutrition & Metabolism, 9: 67)