Effects of carbohydrates on brain tryptophan availability and stress performance

Biol Psychol. 2007 Sep;76(1-2):83-90. doi: 10.1016/j.biopsycho.2007.06.003. Epub 2007 Jun 30.


Although glucose intake has been associated with enhanced mental performance, this does not follow a clear synchronized relationship and findings are inconsistent. Given the brain's need for glucose during demanding conditions, glucose intake may be beneficial for stress performance. Brain serotonin may be involved as a postprandial mechanism initiated by increases in plasma tryptophan to the sum of the other large neutral amino acids (Trp/LNAA ratio). We tested whether carbohydrate drinks compared to placebo drinks increase the plasma Trp/LNAA ratio and improve stress performance and mood. Thirty-seven healthy subjects were monitored in a double-blind placebo-controlled study for performance when continuously exposed to cold pressor stress; 2h after carbohydrate- or placebo-intake. Cold pressor stress significantly increased cortisol and reduced mood and cognitive performance, whereas carbohydrates significantly increased plasma Trp/LNAA and positively influenced performance and mood under stress.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Affect / physiology
  • Amino Acids / metabolism
  • Arousal / physiology*
  • Brain / metabolism*
  • Dietary Carbohydrates / metabolism*
  • Double-Blind Method
  • Female
  • Glucose Solution, Hypertonic / administration & dosage
  • Humans
  • Hydrocortisone / metabolism
  • Male
  • Pain Measurement
  • Stress, Physiological / physiopathology*
  • Tryptophan / metabolism*


  • Amino Acids
  • Dietary Carbohydrates
  • Glucose Solution, Hypertonic
  • Tryptophan
  • Hydrocortisone