Kinetics of L-Theanine Uptake and Metabolism in Healthy Participants Are Comparable after Ingestion of L-Theanine via Capsules and Green Tea
– Source: The Journal of Nutrition, Dec 1, 2012
By Lisa Scheid, Sabine Ellinger, et al.,
[Note: Green tea is a rich source of a family of antioxidants called catechins. One dominant catechin virtually unique to green tea (and mushrooms) is the amino acid called L-theanine. Another well-known catechin unique to green tea is epigallocatechin-3-gallate (EGCG).]
L-Theanine, an amino acid in green tea, is suggested to improve cognition and mood. Therefore, L-theanine is available as a supplement and is now used as an ingredient in functional drinks.
Because data on the metabolic fate of L-theanine from human studies are lacking, we investigated the kinetics of L-theanine uptake and its metabolites [substances produced in the metabolic breakdown of L-theanine], ethylamine and glutamic acid, in healthy participants.
Within a randomized crossover study, 12 participants ingested a bolus of 100 mg L-theanine via capsules or green tea. On further occasions, 3 participants received 50 and 200 mg L-theanine via capsules.
Blood and urine were collected before and up to 24 hours post consumption to determine the concentrations of L-theanine, proteinogenic amino acids, and ethylamine in plasma, erythrocytes, and urine by HPLC.
L-theanine increased in plasma, erythrocytes, and urine with comparable results after both treatments. The maximum plasma concentration of L-theanine occurred 0.8 hours after intake of 100 mg L-theanine via capsules (24.3 +/- 5.7 ?mol/L) and tea (26.5 +/- 5.2 ?mol/L), respectively. The AUC of L-theanine in plasma increased dose dependently after intake of 50, 100, and 200 mg L-theanine via capsules.
Moreover, ethylamine and glutamic acid increased in plasma and were excreted by urine after intake of capsules and tea.
In conclusion, L-theanine is rapidly absorbed and seems to be hydrolyzed [broken down] to ethylamine and glutamic acid.
A minor part of L-theanine is retained in erythrocytes. Kinetics and urinary excretion of L-theanine, ethylamine, and glutamic acid are comparable after both treatments.
Thus, functional effects of L-theanine intake may result from L-theanine, ethylamine, or glutamic acid.
Source: The Journal of Nutrition, Dec 1, 2012. DOI: 10.3945/jn.112.166371, by Scheid L, Ellinger S, Alteheld B, Herholz H, Ellinger J, Henn T, Helfrich HP, Stehle P. Department of Nutrition and Food Science-Nutritional Physiology, and Institute for Numerical Simulation, University of Bonn; Department of Surgery and Department of Urology and Children Urology, University Hospital Bonn; TeeGschwendner, Meckenheim, Germany . [E-mail: firstname.lastname@example.org]