, Volume 52, Issue 5, pp 413–415 | Cite as

The plasma level of some amino acids and physical and mental fatigue

  • E. A. Newsholme
  • E. Blomstrand
Multi-Author Reviews


Tryptophan is converted to 5-hydroxytryptamine (5-HT) in the brain and evidence is presented that an increase in the concentration of 5-HT can result in physical and mental fatigue during prolonged exercise. The entry of tryptophan in the brain is influenced by the plasma level of free tryptophan (that not bound to albumin) and, from competition for entry into brain, by the plasma level of branched chain amino acids. Hence, oral administration of branched chain amino acids could, theoretically, prevent the increase in 5-HT level during exercise and therefore delay physical and mental fatigue. Evidence in support of this hypothesis is presented.

Key words

Tryptophan 5-hydroxytryptamine fatigue branched chain amino acids exercise 


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Copyright information

© Birkhäuser Verlag 1996

Authors and Affiliations

  • E. A. Newsholme
    • 1
  • E. Blomstrand
    • 2
  1. 1.Cellular Nutrition Research Group, Department of BiochemistryUniversity of OxfordOxford(UK)
  2. 2.Pripps Research LaboratoryPripps BryggerierBromma(Sweden)

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