L-Theanine

Your intake

What each level of l-theanine does

Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.

1. Severely lowYOU ARE HERE

   0 mg – 66 mg

   Well below target. Risk of deficiency symptoms tied to calm · focus.

2. Insufficient

   66 mg – 200 mg

   Below the recommended daily target. Long-term adequacy not assured.

3. Adequate

   200 mg – 300 mg

   Daily target met. Standard nutritional support for calm · focus.

4. Therapeutic

   300 mg – 400 mg

   Common for specific health goals. Check the evidence for your situation before sustaining this level.

5. Diminishing returns

   400 mg – +

   Past the point where extra intake typically helps. Evidence for further benefit is thin.

Overview

Amino acid uniquely abundant in green and black tea. Crosses the blood-brain barrier and modulates GABA, glutamate, dopamine, and serotonin. Famous for producing 'alert calm' — used to take the edge off caffeine without sedation.

Functions

• ●Increases alpha brain wave activity (relaxed alertness)
• ●Modest GABA release modulation
• ●Reduces glutamate-driven excitatory tone
• ●Reduces sympathetic stress response markers

Mechanism

Structurally similar to glutamate; binds glutamatergic receptors with low affinity but doesn't trigger excitatory signalling — likely acting as a partial agonist that reduces overall glutamate tone. Increases brain alpha-wave power (8–13 Hz) within 30–40 minutes of oral dosing, an EEG signature of 'relaxed wakefulness'.

Benefits

• ●Reduces stress and anxiety markers in acute stress paradigms
• ●Pairs with caffeine to improve attention and reduce jitters (2:1 theanine:caffeine ratio)
• ●Improves subjective sleep quality in some trials
• ●May modestly reduce blood pressure under acute stress

Deficiency

Not an essential nutrient — no deficiency state. The 'baseline' for theanine is whatever you get from tea consumption.

Excess

Well-tolerated to ~600 mg/day in trials. GRAS status in the US. No established UL.

Forms

• Suntheanine (patented L-theanine)
  Most-studied form; pure L-isomer; consistent potency
• Generic L-theanine
  Pure L-isomer; quality varies by manufacturer
• Racemic theanine (D/L mix)
  Cheaper; D-isomer is biologically inactive
• Tea (green, black, matcha)
  Dietary source; matcha highest by volume

Food sources

• Matcha green tea · 1 cup20–45 mg
• Brewed green tea · 1 cup8–25 mg
• Brewed black tea · 1 cup5–15 mg
• Brewed white tea · 1 cup5–15 mg

Supplement forms

Suntheanine is a patented, consistent L-theanine and the form used in most clinical trials. 100–200 mg is the typical dose. Pairs cleanly with caffeine in a 2:1 theanine:caffeine ratio (e.g. 200 mg theanine + 100 mg caffeine).

Bioavailability

Rapidly absorbed; plasma peaks at ~50 minutes, brain uptake by 90 minutes. Crosses the blood-brain barrier via the leucine-preferring amino acid transporter. Half-life ~3 hours.

Longevity relevance

No direct longevity signal but the stress-reduction and sleep-quality effects are healthspan-relevant. Whole-tea consumption (containing theanine, polyphenols, modest caffeine) correlates with lower all-cause mortality in large cohorts.

Relationships

References

• Examine — Theaninereview
• Hidese — theanine and stress-related symptoms (Nutrients 2019)study
• Owen — theanine + caffeine attention (Nutr Neurosci 2008)study

About L-Theanine

Tea-derived amino acid; alpha-wave EEG activity, calm focus, attenuates caffeine jitters. Common dose 100–400 mg.

Role

Calm · focus

Daily target

200 mg (TR)

Also called

l-theanine, theanine, suntheanine