Adequate high-quality dietary protein is important for muscle protein synthesis. Although, emphasis on specific amino acids within protein, particularly the branched-chain amino acids, which include leucine, isoleucine, and valine, is probably not necessary for most people. It's the leucine that really counts, says Dr. Phillips, and if a person eats sufficient protein, they're probably consuming enough leucine. There are caveats for older adults, who might benefit from a little supplemental leucine to offset their lower protein intake. In this clip, Dr. Stuart Phillips explains the importance of dietary protein quality and the role of the amino acid leucine in muscle protein synthesis.