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

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  • Unno Keiko
    Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka Tea Science Center, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka
  • Yamada Hiroshi
    Division of Drug Evaluation & Informatics, School of Pharmaceutical Sciences, University of Shizuoka
  • Iguchi Kazuaki
    Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka
  • Ishida Hitoshi
    Medicinal Chemistry of Natural Products, School of Pharmaceutical Sciences, University of Shizuoka
  • Iwao Yasunori
    Pharmaceutical Engineering Laboratory, School of Pharmaceutical Sciences, University of Shizuoka
  • Morita Akio
    Department of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University
  • Nakamura Yoriyuki
    Tea Science Center, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka

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  • Anti-stress effect of green tea with lowered caffeine on human: A pilot study

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<p>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).</p>

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