Regular consumption of black tea increases circulating kynurenine concentrations: a randomized controlled trial
Open accessAbstract
BACKGROUND: Circulating neopterin and the ratio of kynurenine to tryptophan (KYN/TRP) concentrations are biomarkers of immune activation that have been linked to cardiovascular and total mortality. Several in vitro studies indicated that tea flavonoids and other antioxidants can modulate tryptophan breakdown rates and neopterin production in immune cells. We aimed to assess the effects of regular black tea consumption on tryptophan and neopterin metabolisms in vivo. METHODS: Participants were healthy individuals, with no major illnesses and having normal to mildly elevated systolic blood pressure. They were randomly assigned to consume 3 cups/day of either powdered black tea solids (tea; n = 45) or a flavonoid-free caffeine-matched beverage (control; n = 49). Serum concentrations of tryptophan, kynurenine and neopterin were assessed at baseline and again at 3 and 6 months after daily ingestion of the respective beverage. RESULTS: Regular consumption of tea over 6 months, compared to control, did not significantly alter neopterin (p = 0.13) or tryptophan (p = 0.85) concentrations, but did result in significantly higher kynurenine (p = 0.016) and KYN/TRP (p = 0.012). Relative to the control group, in the tea group kynurenine and KYN/TRP increased during the treatment period by 0.28 μmol/L (95% CI: - 0.04, 0.60) and 3.2 μmol/mmol (95% CI: - 1.6, 8.0), respectively at 3 months, and by 0.48 μmol/L (95% CI: 0.16, 0.80) and 7.5 μmol/mmol (95% CI: 2.5, 12.5), respectively at 6 months. CONCLUSIONS: Increased circulation of kynurenine and KYN/TRP following regular black tea consumption may indicate enhanced tryptophan breakdown, possibly due to immune activation-induced tryptophan degrading enzyme indoleamine 2,3-dioxygenase. GENERAL SIGNIFICANCE: The influence of black tea consumption on biomarkers of immune system activation could relate to its general health benefits. Data suggests that the net effect strongly depends on the individual immune state, being stimulatory in healthy individuals, while acting more immune dampening in situations with an inflammatory background.
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Other prebiotic dietary components, such as polyphenols, may also modulate kynurenine metabolism.
“Other prebiotic dietary components, such as polyphenols, may also modulate kynurenine metabolism (402, 403).”
From Diet and the Microbiota–Gut–Brain Axis: Sowing the Seeds of Good Mental Health (2021) · cites this paper as [402]
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- Authors
- Gostner, J. M., Becker, K., Croft, K. D., Woodman, R. J., Puddey, I. B., Fuchs, D., & Hodgson, J. M.
- Affiliations
- Innsbruck Medical University (AT)
- The University of Western Australia (AU)
- Flinders University (AU)
- Corresponding author
- Fuchs, D.
- Venue
- BBA Clinical
- Publisher
- Elsevier BV
- Published
- 2015-06
- Volume
- 3
- Pages
- 31-35
- ISSN
- 2214-6474 (ISSN-L)
- PMC
- PMC4661527
- OpenAlex
- W1985740243
- Cited by
- 24
- References
- 32
- Citations by year
- 2026: 1 · 2025: 3 · 2024: 2 · 2023: 2 · 2022: 2 · 2021: 1 · 2020: 3 · 2019: 3 · 2018: 1 · 2017: 1 · 2016: 3 · 2015: 2
- FWCI
- 0.61
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- BBA Clinical (publishedVersion, cc-by-nc-nd)
- PubMed Central (publishedVersion, cc-by-nc-nd)
- PubMed (publishedVersion)
- UWA Profiles and Research Repository (UWA) (submittedVersion, other-oa)
- Funders
- National Health and Medical Research Council of Australia (513744)
- Unilever Research and Development
- Topics
- Life Sciences › Neuroscience › Biological Psychiatry › Tryptophan and brain disorders
- Health Sciences › Medicine › Pathology and Forensic Medicine › Tea Polyphenols and Effects
- Health Sciences › Medicine › Biochemistry › Phytochemicals and Antioxidant Activities
- Keywords
- black tea, kynurenine, kynurenine/tryptophan ratio, tryptophan metabolism, neopterin, immune activation, indoleamine 2,3-dioxygenase, tea flavonoids, antioxidants, cardiovascular mortality, mortality biomarker, dietary intervention, healthy adults, serum biomarkers
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