A Vegetarian Diet Significantly Changes Plasma Kynurenine Concentrations

Biomolecules. 2023 Feb 18;13(2):391. doi: 10.3390/biom13020391.

Abstract

Tryptophan is an essential amino acid and a precursor of a number of physiologically important metabolites, including serotonin, melatonin, tryptamine, and kynurenines. We assessed tryptophan, kynurenines, and vitamin B2 and B6, as well as biomarkers of liver function and inflammation, in a group of 158 female omnivores and vegetarians aged 18-40 years. The majority of women were omnivores, and 22% were vegetarians. Vegetarians had 25% lower serum ALT, significantly higher pyridoxal concentrations, and significantly lower plasma concentrations of most kynurenines, varying from 8% lower concentrations of median plasma kynurenine to 42% lower concentrations of plasma xanthurenic acid, compared to omnivores. No significant differences were observed in vitamin B2 status or in inflammation markers, C-reactive protein and neopterin between the groups. Vegetarians had lower levels of several plasma kynurenines compared to omnivores. The reason for this is unknown; however, lower ALT concentrations, suggesting a better liver status, and a more favourable vitamin B6 status might be contributing factors.

Keywords: C-reactive protein; alanine transaminase; kynurenines; liver; omnivore; tryptophan; vegetarian; vitamin B6.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers
  • Diet, Vegetarian
  • Female
  • Humans
  • Inflammation
  • Kynurenine*
  • Riboflavin
  • Tryptophan*

Substances

  • Kynurenine
  • Tryptophan
  • Riboflavin
  • Biomarkers

Grants and funding

This study was supported by grants from the Foundation to Promote Research Into Functional Vitamin B12 Deficiency and from the Department of Medical Biochemistry and Pharmacology, Haukeland University Hospital. The sponsors of this study had no role in the study design, data collection, data analysis, data interpretation, the writing of the report, or in the decision to submit the paper for publication. The corresponding author has full access to all the data in this study and had the final responsibility to decide to submit it for publication.