title: Kinetics of L-theanine uptake and metabolism in healthy participants are comparable after ingestion of L-theanine via capsules and green tea.
abstract: 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, 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 h postconsumption 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 h after intake of 100 mg L-theanine via capsules (24.3 ± 5.7 μmol/L) and tea (26.5 ± 5.2 μmol/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 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.
authors.affiliation: Department of Nutrition and Food Science-Nutritional Physiology, University of Bonn, Bonn, Germany.
authors.forename: Lisa
authors.initials: L
authors.lastname: Scheid
authors.forename: Sabine
authors.initials: S
authors.lastname: Ellinger
authors.forename: Birgit
authors.initials: B
authors.lastname: Alteheld
authors.forename: Hannes
authors.initials: H
authors.lastname: Herholz
authors.forename: Jörg
authors.initials: J
authors.lastname: Ellinger
authors.forename: Thomas
authors.initials: T
authors.lastname: Henn
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Helfrich
authors.forename: Peter
authors.initials: P
authors.lastname: Stehle
mesh_terms: D000328:Adult; D028241:Camellia sinensis; D002214:Capsules; D018592:Cross-Over Studies; D005260:Female; D005971:Glutamates / Q000008:administration & dosage* / Q000378:metabolism*; D006262:Health; D006801:Humans; D007700:Kinetics; D008297:Male; D013662:Tea / Q000737:chemistry
chemical_list: D002214:Capsules; D005971:Glutamates; D013662:Tea; C026166:theanine