The short answer
May modestly affect relaxation or attention, especially with caffeine, but clinical stress effects are inconsistent.
- Evidence and scope
- Conditional or population-specific
This status does not grade the ingredient for every goal, outcome, or person.
- Important limitation
- Benefit depends on the population, formulation, baseline status, and objective; results should not be generalized.
- Before deciding
- Key concern: Sedatives and blood-pressure medicines may have additive effects; pregnancy data are limited.
01 / PRACTICAL GUIDE
Dose, absorption, and combinations
These are indication-specific reference or studied ranges—not a personalized prescription. Start with the objective, then check the form, label, medicines, and health conditions.
Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.
Dose source ↗Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.
Dose source ↗More is not automatically better. A clinician or product label may specify a different amount.
Water-soluble or readily water-dispersible. This does not mean excess is always harmless.
May be taken with or without food; use earlier if paired with caffeine.
Sedatives and blood-pressure medicines may have additive effects; pregnancy data are limited.
Dose and use links lead to primary or official source material. Search links are discovery tools, not proof that every returned paper applies.
02 / EVIDENCE
What the research says
We keep supportive, mixed, negative, safety, and contextual findings together. The headline never replaces the underlying papers.
These are audited counts for this JIVANA collection, not search-result totals. Participants are counted once when multiple papers use the same cohort; review papers are not added again to participant totals.
Open the research timelineResearch timeline+
Entries are ordered by publication year. A study period appears only when the source reports it.
L-theanine and selective attention in sleep-deprived young adults
L-theanine reduced false alarms and improved target-distractor discrimination. Reaction time improved in both conditions without a significant between-treatment difference; the small simulated task cannot establish safer driving, broad cognition, or chronic benefit.
Study design and methods
- Design
- Double-blind, placebo-controlled, counterbalanced crossover trial
- Population
- 24 healthy adults aged 20–25 after one night of sleep deprivation
- Intervention
- Single L-theanine 200 mg dose versus water placebo
- Outcome
- Traffic-scene visual recognition and reaction performance
L-theanine and stress-related symptoms and cognitive functions in healthy adults
Several self-rated stress and sleep scores improved, with selective cognitive-test signals. The sample was small, outcomes were numerous, and the results do not establish treatment of anxiety, depression, insomnia, or cognitive impairment.
Study design and methods
- Design
- Randomized, double-blind, placebo-controlled crossover trial
- Population
- 30 healthy adults without major psychiatric illness
- Intervention
- L-theanine 200 mg/day versus placebo
- Outcome
- Self-rated depression, trait anxiety, sleep quality, and cognitive tests
Funding or conflict note: Two authors were employees of Taiyo Kagaku, which supplied the L-theanine and placebo.
Unscreened discovery appendix—not evidence3 candidate publicationsSearch run: Aug 21, 2026
Complete for the displayed PubMed query at the search timestamp—not for all databases or every possible synonym. Candidates can be irrelevant, duplicate the same study, or report negative findings. They are never summed as evidence or participants until screened.
03 / SOURCES
Start with the source material
The live search is for discovery only. Search-result counts change and are not included in the audited totals above.
Recent PubMed discovery recordsDirect links to the first 12 records returned by the reproducible search. These are discovery candidates—not reviewed summaries or a count of supportive findings.
- [Clinical evaluation of the efficacy of innovative spread of a given fatty acid composition enriched by adaptogens].Pilipenko VI, Isakov VA, Morozov SV et al. · 2023 · Voprosy pitaniia · PMID 37801460Open on PubMed ↗
- Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study.Baba Y, Inagaki S, Nakagawa S et al. · 2021 · Journal of medicinal food · PMID 33751906Open on PubMed ↗
- Matcha consumption maintains attentional function following a mild acute psychological stress without affecting a feeling of fatigue: A randomized placebo-controlled study in young adults.Baba Y, Kaneko T, Takihara T · 2021 · Nutrition research (New York, N.Y.) · PMID 33744591Open on PubMed ↗
04 / EXPERT CONTEXT
Expert context—not evidence
Expert positions are dated context—not scientific evidence. They never raise the evidence status or become consensus by repetition.
No direct, source-verified endorsement is currently recorded. Research authorship or discussion alone is not treated as endorsement.