AI Article Synopsis

  • L-Theanine, an amino acid found in green tea, is believed to enhance cognitive function and mood, and is available as a supplement in various drinks.
  • A study investigated how L-theanine is absorbed, and its breakdown products, ethylamine and glutamic acid, by examining blood and urine of participants after consuming different doses.
  • Results showed that L-theanine is rapidly absorbed into the bloodstream, with increased levels of its metabolites also observed, suggesting that the cognitive benefits may stem from L-theanine itself or its metabolites.

Article 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.

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http://dx.doi.org/10.3945/jn.112.166371DOI Listing

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Article Synopsis
  • L-Theanine, an amino acid found in green tea, is believed to enhance cognitive function and mood, and is available as a supplement in various drinks.
  • A study investigated how L-theanine is absorbed, and its breakdown products, ethylamine and glutamic acid, by examining blood and urine of participants after consuming different doses.
  • Results showed that L-theanine is rapidly absorbed into the bloodstream, with increased levels of its metabolites also observed, suggesting that the cognitive benefits may stem from L-theanine itself or its metabolites.
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L-theanine intervention enhances human gammadeltaT lymphocyte function.

Nutr Rev

February 2008

Division of Rheumatology, Allergy & Immunology, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.

Human gammadeltaT lymphocytes are a subset of T cells and are a first line of defense against microbes and tumors. These gammadeltaT cells can be primed by nitrogen-containing bisphosphonates, and certain short-chain alkylamines. These primed gammadeltaT cells have an enhanced capacity to proliferate and to secrete cytokines upon ex vivo exposure to a wide variety of microbes and tumor cells.

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