The body requires higher amounts of BCAAs during and following exercise as they are taken up directly by the skeletal muscles versus other amino acids that are first metabolized through the liver. BCAAs are unique in that they can be used to either build new proteins or be burned as fuel to produce energy. The largest amounts of BCAAs can be found in dairy (e.g., milk, whey, and casein), red meat, and eggs. Although they are present in all foods containing protein, supplementing your diet with additional BCAAs provides a definite advantage.
BCAAs have also been shown to have a positive effect on mood and mental function in endurance athletes. Although limited, research supports the idea that the BCAAs can decrease serotonin in the brain (serotonin can cause a sense of tiredness), thereby lowering mental fatigue and maintaining mental acuteness during prolonged endurance exercise. Low levels of the BCAAs also contribute to fatigue and should be replaced following exercise or participation in a competitive event. Research has revealed that the BCAAs help to prevent fatigue and maintain muscle mass and strength during times of physical stress such as intense workouts.