Theanine

Best for

Sharpen focus and mental stamina

Large effect, needs confirmation · 3–400 mg/kg/day for 4 weeks · 2 studies , n=48

17 papers · 6 claims · 54 outcomes scored · 5 positive

Outcomes

What theanine actually does, by outcome

Each row is one outcome with effect size, evidence base, the dose that worked in trials, and time to first effect. Magnitude tiers come from native-unit MCID where available, Cohen's d otherwise.

Outcome Effect size Evidence Dose Weeks Rank

Sharpen focus and mental stamina Large effect, needs confirmation

Concentrate longer, resist distraction, and stay mentally sharp through demanding tasks.

2 RCTs n=48 3–400 mg/kg 4 wk #7/40

38758503·40977612

large

2 RCTs n=48

3–400 mg/kg

4 wk

#7 /40

Ease anxiety in older adults Faint early signal

Quiets the health worries and body tension that build with age.

1 RCT n=18 — 4 wk

39934632

small

1 RCT n=18

—

4 wk

—

Reduce pre-competition anxiety Faint early signal

Quiets the overthinking that hijacks execution right before you compete.

1 RCT n=18 — 4 wk

39934632

small

1 RCT n=18

—

4 wk

—

Reduce daily stress Barely detectable

Everyday pressure stops running your nervous system hot.

6 RCTs n=131 3–400 mg 2–4 wk

23107346·34562208·38758503·40977612 +2 more

trivial

6 RCTs n=131

3–400 mg

2–4 wk

—

Lower day-to-day anxiety Barely detectable

The background hum of worry that colors everything gets quieter.

3 RCTs n=102 3–200 mg/kg 4 wk

31623400·40977612·39934632

trivial

3 RCTs n=102

3–200 mg/kg

4 wk

—

Reduce emotional overwhelm Early signal of harm

The background noise of worry, irritability, and low mood gets quieter.

1 RCT n=30 400 mg 4 wk

38758503

large

1 RCT n=30

400 mg

4 wk

—

Outcome	Effect	Evidence	Dose	Weeks	Rank
Sharpen focus and mental stamina Large effect, needs confirmation	large	2 RCTs n=48	3–400 mg/kg	4 wk	#7/40
Ease anxiety in older adults Faint early signal	small	1 RCT n=18	—	4 wk	—
Reduce pre-competition anxiety Faint early signal	small	1 RCT n=18	—	4 wk	—
Reduce daily stress Barely detectable	trivial	6 RCTs n=131	3–400 mg	2–4 wk	—
Lower day-to-day anxiety Barely detectable	trivial	3 RCTs n=102	3–200 mg/kg	4 wk	—
Reduce emotional overwhelm Early signal of harm	large	1 RCT n=30	400 mg	4 wk	—

Buy well

Recommended Theanine products

Real products that dose Theanine where the research does, in a clean formulation, from brands we've audited. We only list ones we'd stand behind.

Chosen for adequate Theanine dosing vs. the studied range, a clean formulation (grade A–C), and independent brand-quality audits. Not sponsored.

Risk profile

Adverse events and known drug interactions

Safety events

massive bleeding severe

fatigue moderate

toe injury moderate

digestive symptoms (bloating, constipation) mild

dizziness mild

nausea mild

headache mild

gastrointestinal disturbances mild

Drug interactions

Doxorubicin major additive

Morphine moderate decreases effect

Capecitabine moderate decreases effect

Oxaliplatin moderate unknown

Nicotine moderate decreases effect

Tetrahydrocannabinol minor decreases effect

Mecamylamine minor decreases effect

Co-studied with

Supplements that share evidence with theanine

Sources

Generated August 14, 2026

Theanine

What theanine actually does, by outcome

Recommended Theanine products

Adverse events and known drug interactions

Supplements that share evidence with theanine

More evidence for Theanine

Calm Without the Brake: How a Tea Molecule Trains the Mind to Relax and Focus

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Theanine

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More evidence for Theanine

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NewSleep: evidence map across 37 supplements

NewStress: evidence map across 46 supplements

Calm Without the Brake: How a Tea Molecule Trains the Mind to Relax and Focus

Best Supplements for Deep, Restful Sleep (2026)

Best Supplements to Increase Deep, Restorative Sleep (2026)

The 10 Supplements With Real Evidence for Faster Thinking

Sleep: evidence map across 37 supplements

Stress: evidence map across 46 supplements