Anti-stress effect of green tea with lowered caffeine on humans: a pilot study
Open accessAbstract
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).
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It was not possible to pool data from the 8 trials reporting sleep outcomes, so their results were described in a narrative synthesis.
“A subset of 8 trials presented in 8 references56,57,65,74–77,80 reported sleep outcomes (Table 2). It was not possible to pool the data from these studies so instead their results were described in a narrative synthesis.”
Three studies of students undertaking pharmacy practice reported no significant differences in subjective sleep time between groups consuming green tea, theanine, or placebo.
“Three studies of students undertaking pharmacy practice reported no significant differences in subjective sleep time between groups consuming green tea, theanine, or placebo.74,75,77”
Improvements in anxiety symptoms were often accompanied by improvements in biomarkers including salivary alpha-amylase, cortisol, chromogranin A, and immunoglobulin A.
“An overall improvement in anxiety symptoms was often accompanied by improvements in biomarkers, including salivary α-amylase, cortisol, chromogranin A and immunoglobulin A [27][28][29][30].”
From Psychotropic effects of L-theanine and its clinical properties: from the management of anxiety and stress to a potential use in schizophrenia (2019) · cites this paper as [28]
Only three studies were found that investigated the effects of green tea intake on anxiety and stress parameters.
“However, we found only three studies [28,30,37] that have investigated the effects of green tea intake on parameters of anxiety and stress.”
From Psychotropic effects of L-theanine and its clinical properties: from the management of anxiety and stress to a potential use in schizophrenia (2019) · cites this paper as [28]
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- Authors
- Unno, K., Yamada, H., Iguchi, K., Ishida, H., Iwao, Y., Morita, A., & Nakamura, Y.
- Affiliations
- Shizuoka University (JP)
- Venue
- Biological & Pharmaceutical Bulletin
- Publisher
- Pharmaceutical Society of Japan
- Published
- 2017
- Volume
- 40
- Issue
- 6
- Pages
- 902-909
- ISSN
- 0918-6158 (ISSN-L)
- 1347-5215
- OpenAlex
- W2617754544
- Cited by
- 29
- References
- 37
- Citations by year
- 2026: 1 · 2025: 5 · 2023: 1 · 2022: 3 · 2021: 10 · 2020: 2 · 2019: 5 · 2018: 1 · 2017: 1
- FWCI
- 1.93
- Type
- journal article
- Language
- en
- Open access
- diamond
- doi.org
- Locations
- Biological and Pharmaceutical Bulletin (publishedVersion)
- PubMed (publishedVersion)
- Funders
- University of Chicago
- Japan Society for the Promotion of Science (23617014)
- Topics
- Health Sciences › Medicine › Pathology and Forensic Medicine › Tea Polyphenols and Effects
- Health Sciences › Medicine › Complementary and alternative medicine › Medicinal Plant Extracts Effects
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Medicinal Plants and Bioactive Compounds
- Keywords
- theanine, caffeine, anti-stress effects, anxiety, salivary amylase, stress response, pharmacy students, tea catechins, placebo-controlled
- MeSH terms
- Adult, Amino Acids, Caffeine, Catechin, Female, Humans, Male, Pilot Projects, Stress, Psychological, Tea, Anti-Anxiety Agents, Single-Blind Method, Salivary alpha-Amylases, Young Adult
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