Tryptophan metabolism in animals: important roles in nutrition and health

Front Biosci (Schol Ed). 2011 Jan 1;3:286-97. doi: 10.2741/s152.


L-Tryptophan is a nutritionally essential amino acid for monogastric animals and preweaning ruminants because it cannot be synthesized in the body. Besides serving as a building block for proteins, tryptophan is a critical nutrient for the functions of nervous and immune systems. Over the past decades, much attention has been directed to study the role of tryptophan as a limiting amino acid in mammalian and avian nutrition. However, emerging evidence from recent studies shows that tryptophan and its metabolites (e.g., serotonin (5-hydroxytryptamine, 5-HT) and melatonin)) can regulate feed intake, reproduction, immunity, neurological function, and anti-stress responses. Additionally, tryptophan may modulate gene expression and nutrient metabolism to impact whole-body homeostasis in organisms. Thus, adequate intake of this amino acid from the diet is crucial for growth, development, and health of animals and humans.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animal Nutritional Physiological Phenomena / physiology*
  • Animals
  • Gene Expression Regulation / physiology*
  • Homeostasis / physiology*
  • Humans
  • Melatonin / metabolism
  • Nervous System / metabolism*
  • Niacin / metabolism
  • Nutritional Requirements
  • Serotonin / metabolism
  • Tryptophan / administration & dosage
  • Tryptophan / immunology*
  • Tryptophan / metabolism*


  • Niacin
  • Serotonin
  • Tryptophan
  • Melatonin