Trial reportJournal of physiological anthropology2012
Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses.
Trial report in Journal of physiological anthropology, 2012. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 32 papers, 5 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
32 citing papers in PubMed, 5 syntheses or guidelines pooled it, 106 citations in OpenAlex.
- Cognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials.Molecular psychiatry · 2026Pooled it
- A CE/TA-stratified systematic review and evidence map of matcha and green tea bioactives in endocrine stress regulation: testosterone, cortisol, and the T:C ratio.Frontiers in nutrition · 2026Pooled it
- Pooled it
- The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.Plant foods for human nutrition (Dordrecht, Netherlands) · 2020Pooled it
- Examining techniques for measuring the effects of nutrients on mental performance and mood state.European journal of nutrition · 2016Pooled it
- Effects of heat-treatedFrontiers in nutrition · 2026Trial
- Trial
- Trial
- Effects of Matcha Green Tea Powder on Cognitive Functions of Community-Dwelling Elderly Individuals.Nutrients · 2020Trial
- Trial
- Harnessing Photosynthetic ATP for Whole-Cell Biocatalysis in the CyanobacteriumACS sustainable chemistry & engineering · 2025Article
- Promising, but Not Completely Conclusive-The Effect of l-Theanine on Cognitive Performance Based on the Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Clinical Trials.Journal of clinical medicine · 2025Review
- Urinary metabolites associated with the long-term risk for chronic kidney disease incidence and progression in hypertensive patients.Metabolomics : Official journal of the Metabolomic Society · 2025Article
- Review
- Tea consumption may improve psychological resilience among older adults with chronic diseases: a prospective cohort study.Frontiers in psychiatry · 2025Article
- Preparation of Transdermal Gel Containing l-Theanine for the Potential Treatment of Premenstrual Syndrome: A Preclinical Study.Women's health reports (New Rochelle, N.Y.) · 2024Article
- Dietary Strategies for Relieving Stress in Pet Dogs and Cats.Antioxidants (Basel, Switzerland) · 2023Review
- The therapeutic potential of matcha tea: A critical review on human and animal studies.Current research in food science · 2023Review
- Acute Effect of a Dietary Multi-Ingredient Nootropic as a Cognitive Enhancer in Young Healthy Adults: A Randomized, Triple-Blinded, Placebo-Controlled, Crossover Trial.Frontiers in nutrition · 2022Article
- Review
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
4 authors at 1 institution in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundL-theanine, an amino acid contained in green tea leaves, is known to block the binding of L-glutamic acid to glutamate receptors in the brain, and has been considered to cause anti-stress effects by inhibiting cortical neuron excitation. Both L-theanine and caffeine, which green tea contains, have been highlighted for their beneficial effects on cognition and mood.
methodsIn this study, we investigated the effects of orally administered L-theanine or caffeine on mental task performance and physiological activities under conditions of physical or psychological stress in humans. Fourteen participants each underwent three separate trials, in which they orally took either L-theanine + placebo, caffeine + placebo, or placebo only.
resultsThe results after the mental tasks showed that L-theanine significantly inhibited the blood-pressure increases in a high-response group, which consisted of participants whose blood pressure increased more than average by a performance of a mental task after placebo intake. Caffeine tended to have a similar but smaller inhibition of the blood-pressure increases caused by the mental tasks. The result of the Profile of Mood States after the mental tasks also showed that L-theanine reduced the Tension-Anxiety scores as compared with placebo intake.
conclusionsThe findings above denote that L-theanine not only reduces anxiety but also attenuates the blood-pressure increase in high-stress-response adults.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.