Mood/Sleep/Cognition

L-Theanine

Tea amino acid that promotes calm focus and may improve stress, sleep, and attention in adults under mental load.

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Quick Take

Useful for calm focus or evening wind-down; effects are real but usually modest, not dramatic.

L-theanine is a non-protein amino acid found mainly in green and black tea, with smaller amounts in some mushrooms. It crosses the blood-brain barrier and modulates glutamate signaling while increasing alpha-wave activity linked to relaxed wakefulness. Best-supported uses are lowering perceived stress, modestly improving sleep quality, and improving attention when paired with caffeine. It tends to help most in stressed adults and people who want smoother, calmer stimulation.

Potential benefits

Reduces stress and anxiety

Improves sleep quality

May improve attention with caffeine

May reduce mental fatigue

May reduce caffeine jitters

Protocol

Amount

100-200 mg

Frequency

Once or twice daily

When

30-60 minutes before a stressful task, with caffeine, or before bed; with or without food.

Onset Time

30-60 min for calm/focus; 1-2 weeks for sleep with daily use

Who Should Consider

Adults with stress-related tension

People sensitive to caffeine jitters

Tea or coffee drinkers wanting calmer focus

Adults with mild stress-related sleep issues

Students or desk workers under mental load

Food Sources

Green tea (~8-25 mg per cup)
Black tea (~5-20 mg per cup)
Matcha (~20-40 mg per 2 g serving, variable)
Shade-grown teas like gyokuro (~20-50 mg per cup, variable)

How It Works

L-theanine crosses into the brain and interacts with glutamate pathways, which can reduce mental overstimulation. It also increases alpha-wave activity associated with relaxed alertness and appears to influence GABA, dopamine, and stress-response signaling.

Updated 5/19/2026