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AMINO ACIDS

L-Theanine (Suntheanine)

Calm focus · stress

STRONG EVIDENCEVEGANREAD THE RESEARCH
Written to our editorial standards · reviewed against published research· Updated 2 Jun 2026
Last reviewed: May 30, 2026
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L-Theanine: Calm focus · stress. Promotes alpha brain waves, calm, focused energy without sedation. Pairs beautifully with coffee. Standard dose 200 mg, taken in the midday, about $12/month. Evidence rating: strong evidence.

What is L-Theanine?

L-Theanine is a unique amino acid found almost exclusively in tea leaves, particularly green tea. It crosses the blood-brain barrier and promotes the production of alpha brain waves, the electrical pattern associated with calm, focused alertness without sedation. This is why a cup of green tea feels different from coffee even when both contain caffeine. Clinical research supports L-theanine for anxiety reduction, focus enhancement, and as a companion to caffeine to smooth the stimulant edge while extending its benefits. The Suntheanine branded form is pure L-isomer (not the racemic DL mix) and is the form used in most published studies. Standard dose is 100-400 mg.

WHY IT MATTERS

Promotes alpha brain waves, calm, focused energy without sedation. Pairs beautifully with coffee.

Natural food sources

Where possible, get L-Theanine from whole foods first. Common dietary sources include:

Green teaBlack teaMatcha

Where to buy

NOW Foods L-Theanine 200mg with Suntheanine
RECOMMENDED
Now Foods, L-Theanine
200 mg · Midday · ~$12/month

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All product options

NOW Foods L-Theanine 200mg with SuntheanineBESTSELLER
L-Theanine 200mg with Suntheanine
NOW Foods
120 veg capsules · $18 · ★ 4.7
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Doctor's Best Suntheanine L-TheanineEDITOR'S PICK
Suntheanine L-Theanine
Doctor's Best
90 veg capsules · $16 · ★ 4.7
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Jarrow Formulas Theanine 200PREMIUM
Theanine 200
Jarrow Formulas
60 veg capsules · $19 · ★ 4.7
Buy on iHerb →Buy on Amazon →

Stacks that include L-Theanine

☾
The Sleep Stack
Deeper sleep, fewer trips to the bathroom.
✦
The Focus Stack
Sharper mind, calmer attention.
♡
The Stress Stack
Calmer baseline, no sedation.

Best for your goal

Interactions

Other amino acids

Glycine
Sleep depth · core body temperature
N-Acetyl Cysteine (NAC)
Liver · antioxidant · respiratory
Taurine
Heart · sleep · cellular hydration
Acetyl-L-Carnitine (ALCAR)
Brain energy · focus · fat metabolism

Common questions

What is L-Theanine?
L-Theanine is a unique amino acid found almost exclusively in tea leaves, particularly green tea. It crosses the blood-brain barrier and promotes the production of alpha brain waves, the electrical pattern associated with calm, focused alertness without sedation. This is why a cup of green tea feels different from coffee even when both contain caffeine. Clinical research supports L-theanine for anxiety reduction, focus enhancement, and as a companion to caffeine to smooth the stimulant edge while extending its benefits. The Suntheanine branded form is pure L-isomer (not the racemic DL mix) and is the form used in most published studies. Standard dose is 100-400 mg.
What is L-Theanine used for?
Calm focus · stress. Promotes alpha brain waves, calm, focused energy without sedation. Pairs beautifully with coffee.
What is the standard dose of L-Theanine?
200 mg, typically taken in the midday. Approximate cost is $12 per month.
How strong is the evidence for L-Theanine?
Strong evidence for its primary uses. See the full study list on the research page.

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