L-tryptophan: Basic metabolic functions, behavioral research and therapeutic indications

Dawn M. Richard, Michael A. Dawes, Charles W. Mathias, Ashley Acheson, Nathalie Hill-Kapturczak, Donald M. Dougherty

Research output: Contribution to journalReview articlepeer-review

386 Scopus citations


An essential component of the human diet, L-tryptophan is critical in a number of metabolic functions and has been widely used in numerous research and clinical trials. This review provides a brief overview of the role of L-tryptophan in protein synthesis and a number of other metabolic functions. With emphasis on L-tryptophan's role in synthesis of brain serotonin, details are provided on the research uses of L-tryptophan, particularly L-tryptophan depletion, and on clinical trials that have been conducted using L-tryptophan supplementation. The ability to change the rates of serotonin synthesis in the brain by manipulating concentrations of serum tryptophan is the foundation of much research. As the sole precursor of serotonin, experimental research has shown that L-tryptophan's role in brain serotonin synthesis is an important factor involved in mood, behavior, and cognition. Furthermore, clinical trials have provided some initial evidence of L-tryptophan's efficacy for treatment of psychiatric disorders, particularly when used in combination with other therapeutic agents.

Original languageEnglish (US)
Pages (from-to)45-60
Number of pages16
JournalInternational Journal of Tryptophan Research
Issue number1
StatePublished - 2009


  • Clinical uses
  • Depletion
  • L-tryptophan
  • Loading
  • Metabolism
  • Therapeutics

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology


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