Regular consumption of black tea increases circulating kynurenine concentrations: A randomized controlled trial
J M Gostner1, K Becker2, K D Croft3
1Division of Medical Biochemistry, Medical University of Innsbruck, Austria.
BBA Clinical
|December 18, 2015
Summary
Regular black tea consumption increased kynurenine and the kynurenine/tryptophan ratio in healthy individuals, suggesting enhanced tryptophan breakdown. This immune activation may explain some of tea's health benefits.
Area of Science:
- Immunology
- Nutritional Science
- Biochemistry
Background:
- Circulating neopterin and kynurenine/tryptophan (KYN/TRP) ratio are biomarkers of immune activation linked to mortality.
- In vitro studies suggest tea flavonoids modulate tryptophan metabolism and neopterin production.
Purpose of the Study:
- To assess the in vivo effects of regular black tea consumption on tryptophan and neopterin metabolism.
- To investigate the impact of black tea on biomarkers of immune activation.
Main Methods:
- Healthy participants were randomized to consume 3 cups/day of black tea or a flavonoid-free control beverage for 6 months.
- Serum concentrations of tryptophan, kynurenine, and neopterin were measured at baseline, 3 months, and 6 months.
Main Results:
- Black tea consumption did not significantly alter neopterin or tryptophan levels.
- Significant increases in kynurenine and the KYN/TRP ratio were observed in the tea group compared to the control group after 6 months.
- Kynurenine increased by 0.48 μmol/L and KYN/TRP by 7.5 μmol/mmol at 6 months in the tea group.
Conclusions:
- Increased kynurenine and KYN/TRP suggest enhanced tryptophan breakdown, potentially via indoleamine 2,3-dioxygenase, indicating immune activation.
- Black tea's effect on immune biomarkers may depend on the individual's immune status, showing stimulatory effects in healthy individuals.
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