L-Theanine human research evidence

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Public-ready7/5/2026

L-Theanine

Papers analyzed

Cognition, memory, and focusStress Response and Sleep Changes

Main benefit evidence

Review human evidence by goal.

Cognition and focus

Cognition, memory, and focus

Goal tierB

Direct human evidence

Some accumulation4 direct studies

Positive

No clear difference

Mixed

Negative

Positive study ratio75%

This is the share of verified direct studies with a positive result, not your personal chance of benefit.

Research intake observed

One study used 200 mg/day.

Dose confirmed in 1 of 4 direct studies.

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200 mg/day

rct

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Sleep

Stress Response and Sleep Changes

Goal tierNot rated yet

No direct evidence for general supplement use is confirmed under the current standard.

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Side effects and combination findings in studies

Findings from studies of this ingredient alone are separated from findings involving another supplement or medication.

Caution signals

Side effects + combos + curated rules

Key precautions

No combination caution signal is clear enough to show right now. This does not guarantee safety.

1 combo signals and 0 added-signal combos shown below.

These are signals reported in studies. They do not predict what will happen to an individual.

Positive combinations studied

Positive combination findings are separated by how the study compared the groups. This is not a recommendation to combine them.

Positive findings when used together

The combination had a positive result, but the contribution of each ingredient could not be separated.

CaffeineL-theanine combined with caffeine significantly reduced caffeine-induced tachycardia (17% vs 92%) and state anxiety compared to caffeine alone.

L-Theanine

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