The Importance of Non-essential Amino Acids for Maintaining Skeletal Muscle Protein Synthesis Rates in Healthy Young Men

Background: Protein intake is important for maintaining skeletal muscle mass. These proteins consist of a collection of small building blocks which are called amino acids. There are two types of amino acids that are needed to build muscle: essential amino acids (EAA) and non-essential amino acids (NEAA). EAAs cannot be made in the body and must be consumed through foods, while NEAAs can be made within the body. However, if NEAA are not consumed through foods, the process of making NEAA in the body costs the body energy. It is still unknown what the impact of a diet containing too few non-essential amino acids is for muscle building and the body's energy metabolism. Objective: To determine if a diet lacking NEAA, with or without being replaced by additional EAA, influences muscle protein building and whole-body metabolism. Study design: Randomized, parallel design, double-blind, 10-day dietary intervention study. Study population: 45 healthy (BMI 22-30 kg/m2) young males (age: 18-35 y inclusive). Hypothesis: It is hypothesized that a diet lacking NEAA, with or without being replaced by additional EAA, decreases muscle protein building in humans.