For people with low dietary protein intake, BCAA supplementation can promote muscle protein synthesis and increase muscle growth over time. Supplementation can also be used to prevent fatigue in novice athletes.
Leucine plays an important role in muscle protein synthesis, while isoleucine induces glucose uptake into cells. Further research is needed to determine valine’s role in a BCAA supplement.
Supplementing BCAAs prevents a serum decline in BCAAs, which occurs during exercise. A serum decline would normally cause a tryptophan influx into the brain, followed by serotonin production, which causes fatigue.
BCAAs are important to ingest on a daily basis, but many protein sources, such as meat and eggs, already provide BCAAs. Supplementation is unnecessary for people with a sufficiently high protein intake (1-1.5g per kg of bodyweight a day or more).