NootroWorld
L-Theanine illustration

L-Theanine

An amino acid from green tea. Modest solo effects on stress; stronger effects in the 200 mg L-theanine + 100 mg caffeine stack on attention and reduced jitter.

Aminos Last verified 2026-05-06
focus stress and mood

What it does

L-Theanine increases EEG alpha-wave activity and reduces caffeine's blood-pressure rise and subjective jitter. The 1:2 caffeine to L-theanine ratio (100 mg + 200 mg) is the most-trialed cognitive stack on the market.

  • Reduced acute stress and state anxiety Moderate evidence

    200 mg attenuates self-reported state anxiety, salivary cortisol, and produces alpha-wave shifts after an acute stress challenge. Chronic 200 mg/day for 4 weeks lowers STAI-trait and depression scores.

    Sources: PMID 34557606 · PMID 31623400

  • Improved attention with caffeine Moderate evidence

    L-theanine + caffeine improves switch-task accuracy and selective attention; effects exceed either compound alone. Solo L-theanine effects on cognition are smaller and less consistent.

    Sources: PMID 21040626 · PMID 35095143

  • Alpha-wave (relaxed-alert) state Moderate evidence

    Single 200 mg dose increases EEG alpha power 30 to 45 minutes post-ingestion, the proposed mechanism for 'calm focus' without sedation.

    Sources: L-theanine on attention and reaction time response (Higas...

Top picks

  1. 1

    Sports Research

    Double Strength L-Theanine 200 mg (Suntheanine)

    Suntheanine softgels; 200 mg per cap matches the trial-tested dose.

    Check on Amazon
  2. 2

    NOW Foods

    L-Theanine 200 mg

    Double-strength veg capsules at the trial dose. NSF GMP facility; verify the label for L-isomer purity if Suntheanine sourcing is required.

    Check on Amazon
  3. 3

    Pure Encapsulations

    L-Theanine 200 mg (Suntheanine)

    Practitioner-channel brand; clean inactives.

    Check on Amazon

Affiliate disclosure: NootroWorld may earn a commission from qualifying Amazon purchases made through these links, at no extra cost to you. NootroScore and editorial rankings are calculated independently of any affiliate relationship. More on how we make money.

How to use it

Dosage
100 to 400 mg per dose; 200 mg is the most-replicated point. 100 mg caffeine + 200 mg L-theanine is the canonical stack ratio.
Timing
30 to 60 minutes before the desired effect window (focus session, stressor, bedtime if taken solo for relaxation).
With food
Not required
Onset
30 to 60 minutes acutely.

What to look for

  • Suntheanine on the label (>99% pure L-isomer, fermentation-derived). Cheap synthetic theanine is racemic with ~50% inactive D-form.
  • Per-capsule dose of 100 to 200 mg, not 50 mg blend caps.
  • Avoid blend dilution: many 'calm' or 'focus' stacks bury 50 to 100 mg L-theanine inside a proprietary blend.
  • Third-party testing (USP, NSF, Informed Sport).
  • Capsules and softgels equivalent. Powder is cheapest per mg but harder to dose.

Formats: capsules, softgels, powder, gummies.

Skip if:
  • Antihypertensive medications (additive blood-pressure lowering).
  • CNS depressants or sedatives (additive drowsiness).
  • Pregnancy or breastfeeding (insufficient safety data).
  • Stimulant-sensitive users with low resting blood pressure.

FAQ

Solo or with caffeine?
Both work. Solo is mild and good for trimming social-anxiety edge. With caffeine is where most users feel a clear focus effect.

Related comparisons

Additional references