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

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


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).

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

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Amino Acids / analysis
  • Anti-Anxiety Agents / therapeutic use*
  • Caffeine / analysis*
  • Catechin / analogs & derivatives
  • Catechin / analysis
  • Female
  • Humans
  • Male
  • Pilot Projects
  • Salivary alpha-Amylases / analysis
  • Single-Blind Method
  • Stress, Psychological / enzymology
  • Stress, Psychological / therapy*
  • Tea*
  • Young Adult


  • Amino Acids
  • Anti-Anxiety Agents
  • Tea
  • Caffeine
  • Catechin
  • Salivary alpha-Amylases