L-Theanine

evidence score

amino acid

208 studies

theaninegamma-ethylamino-L-glutamic acidSuntheanine+1 more

L-Theanine is an amino acid found naturally in green and black tea (Camellia sinensis). It promotes a state of relaxed alertness — reducing anxiety without causing sedation — and is particularly well-studied in combination with caffeine. It increases alpha brain wave activity (8-14 Hz), modulates GABA and glutamate systems, and has a strong safety profile with minimal side effects. The caffeine+theanine stack (1:2 ratio) is among the most replicated cognitive enhancement combinations in the literature.

Evidence

Moderate evidence

Safety

Unknown safety profile

Clinical Status

No formal phase listed

Research Sync

Feb 19, 2026

Dosing

Typical

200 mg

100 mgRange400 mg

Frequencydaily or as needed

Set height & weight in Settings to see your dose.

Pharmacology

Half-life~1 hour (plasma)

Onset30-60 minutes

Duration3-5 hours

Routes

oral

Evidence Score

Level B — Moderate

208 studies indexed · 3 meta-analyses

Scoring Factors

Volume(40%)~46/100

Quality(30%)~47/100

Sample Size(10%)~100/100

Consistency(10%)~100/100

Replication(5%)~100/100

Recency(5%)~100/100

Scores estimated from study counts. Exact breakdown computed after research sync.

Evidence Levels

AScore ≥75 with at least 1 meta-analysis and 3+ RCTs

BScore ≥50 with at least 1 RCT or meta-analysis

CScore ≥25 — observational or animal evidence only

DScore <25 — very limited or preclinical data

Plain-English Snapshot

L-Theanine is currently categorized as a amino acid compound.

Evidence is moderate (73/100): promising signal from 208 indexed studies, but context and population still matter.

Safety scoring is incomplete. Start conservatively and monitor carefully.

Core mechanism

GABA-A positive allosteric modulation, NMDA/AMPA antagonism, alpha-wave induction, catecholamine modulation

Practical Context

Strongest current signals

Level A: Examining the effect of L-theanine on sleep: a systematic review of dietary supplementation trials.
Level A: Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Level A: Efficiency of Different Supplements in Alleviating Symptoms of ADHD with or Without the Use of Stimulants: A Systematic Review.