Amino Acids

, Volume 45, Issue 5, pp 1133–1142 | Cite as

Oral branched-chain amino acid supplements that reduce brain serotonin during exercise in rats also lower brain catecholamines

  • SuJean Choi
  • Briana DiSilvio
  • Madelyn H. Fernstrom
  • John D. FernstromEmail author
Original Article


Exercise raises brain serotonin release and is postulated to cause fatigue in athletes; ingestion of branched-chain amino acids (BCAA), by competitively inhibiting tryptophan transport into brain, lowers brain tryptophan uptake and serotonin synthesis and release in rats, and reputedly in humans prevents exercise-induced increases in serotonin and fatigue. This latter effect in humans is disputed. But BCAA also competitively inhibit tyrosine uptake into brain, and thus catecholamine synthesis and release. Since increasing brain catecholamines enhances physical performance, BCAA ingestion could lower catecholamines, reduce performance and thus negate any serotonin-linked benefit. We therefore examined in rats whether BCAA would reduce both brain tryptophan and tyrosine concentrations and serotonin and catecholamine synthesis. Sedentary and exercising rats received BCAA or vehicle orally; tryptophan and tyrosine concentrations and serotonin and catecholamine synthesis rates were measured 1 h later in brain. BCAA reduced brain tryptophan and tyrosine concentrations, and serotonin and catecholamine synthesis. These reductions in tyrosine concentrations and catecholamine synthesis, but not tryptophan or serotonin synthesis, could be prevented by co-administering tyrosine with BCAA. Complete essential amino acid mixtures, used to maintain or build muscle mass, were also studied, and produced different effects on brain tryptophan and tyrosine concentrations and serotonin and catecholamine synthesis. Since pharmacologically increasing brain catecholamine function improves physical performance, the finding that BCAA reduce catecholamine synthesis may explain why this treatment does not enhance physical performance in humans, despite reducing serotonin synthesis. If so, adding tyrosine to BCAA supplements might allow a positive action on performance to emerge.


Exercise Tryptophan Tyrosine Serotonin Catecholamines Rat 



These studies were supported by a grant from Ajinomoto North America.

Conflict of interest

John D. Fernstrom is an occasional scientific consultant to the Ajinomoto Company on matters unrelated to the content of this manuscript. The other authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag Wien 2013

Authors and Affiliations

  • SuJean Choi
    • 1
  • Briana DiSilvio
    • 2
  • Madelyn H. Fernstrom
    • 2
  • John D. Fernstrom
    • 2
    • 3
    Email author
  1. 1.Department of Biomedical SciencesMarquette UniversityMilwaukeeUSA
  2. 2.Departments of Psychiatry, Pharmacology and Chemical BiologyUniversity of Pittsburgh School of MedicinePittsburghUSA
  3. 3.UPMC/Western Psychiatric Institute and ClinicPittsburghUSA

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