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Biol Pharm Bull. 2017;40(6):902-909. doi: 10.1248/bpb.b17-00141.

Anti-stress Effect of Green Tea with Lowered Caffeine on Humans: A Pilot Study.

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Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka.
Tea Science Center, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka.
Division of Drug Evaluation & Informatics, School of Pharmaceutical Sciences, University of Shizuoka.
Medicinal Chemistry of Natural Products, School of Pharmaceutical Sciences, University of Shizuoka.
Pharmaceutical Engineering Laboratory, School of Pharmaceutical Sciences, University of Shizuoka.
Department of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University.


Theanine, an amino acid in tea, has significant anti-stress effects on animals and humans. However, the effect of theanine was blocked by caffeine and gallate-type catechins, which are the main components in tea. We examined the anti-stress effect of green tea with lowered caffeine, low-caffeine green tea, on humans. The study design was a single-blind group comparison and participants (n=20) were randomly assigned to low-caffeine or placebo tea groups. These teas (≥500 mL/d), which were eluted with room temperature water, were taken from 1 week prior to pharmacy practice and continued for 10 d in the practice period. The participants ingested theanine (ca. 15 mg/d) in low-caffeine green tea. To assess the anxiety of participants, the state-trait anxiety inventory test was used before pharmacy practice. The subjective stress of students was significantly lower in the low-caffeine-group than in the placebo-group during pharmacy practice. The level of salivary α-amylase activity, a stress marker, increased significantly after daily pharmacy practice in the placebo-group but not in the low-caffeine-group. These results suggested that the ingestion of low-caffeine green tea suppressed the excessive stress response of students. This study was registered at the University Hospital Medical Information Network (ID No. UMIN14942).


anti-stress effect; clinical study; green tea; salivary α-amylase; theanine

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