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L-Theanine - Benefits, Dosage & Safety Information | Herbal Advisor

L-Theanine

Mood SupportMODERATE EvidenceHealth Canada source available21 PubMed studiesNIH DSLD listedISR Cached

L-theanine is a naturally occurring amino acid found primarily in green tea that crosses the blood-brain barrier to modulate neurotransmitter activity. It is used to promote relaxation, reduce stress, and support cognitive function without causing sedation or impairment.

Health Benefits

✓

Promotes relaxation and reduces perceived stress without drowsiness

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Enhances alpha brain wave activity associated with calm alertness

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Supports attention and focus, particularly when combined with caffeine

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May improve sleep quality and reduce sleep latency

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Supports healthy cortisol response to acute stress

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Enhances mood through modulation of serotonin and dopamine

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Promotes cardiovascular relaxation via blood pressure support

Sources: Health Canada LNHPD View full source list →

Dosage Guidelines:

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100–200 mg once or twice daily

Sources: Health Canada LNHPD View full source list →

Safety & Side Effects:

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Headache (rare, typically at higher doses)

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Mild gastrointestinal upset or nausea in sensitive individuals

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Drowsiness or excessive relaxation at doses above 200 mg

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Dizziness in isolated cases

Sources: Health Canada LNHPD View full source list →

Regulatory sources

This ingredient appears in licensed Canadian natural health products in Health Canada's LNHPD.

Health Canada source available

Matched ingredient: L-Theanine
Match confidence: High
Licensed product records: 1763
Common forms: Capsule (927), Powder (360), Tablet (94)

Approved purpose examples

-(Used as a) sleep aid (to help promote sleep). Helps (to) prevent and/or reduce the effects of jet lag/minimize jet lag (e.g. daytime fatigue, sleep disturbance) (for people/if travelling by plane easterly across two or more time zones/flying east over two or more time zones) Helps (to) re-set the body’s sleep-wake cycle (aspect of the circadian rhythm). Helps (to) speed up/reduce the time it takes to fall asleep (sleep onset latency aspect of sleep quality) in people who fall asleep slowly/with delayed sleep phase disorder. Helps increase the total sleep time (aspect of sleep quality) in people suffering from sleep restriction or altered sleep schedule (e.g. shift-work and jet lag). Helps to temporarily promote relaxation.
-Helps to temporarily promote relaxation. A factor in normal growth and development. A factor in the maintenance of good health. Contributes to maintaining general health. For maintaining general health. Helps in energy metabolism/(and) tissue formation. Helps to maintain/support normal electrolyte balance. Helps to maintain/support normal muscle function. Maintains/supports good health. Mineral supplement. Source of/Provides (an) electrolyte(s) for the maintenance of good health. Source of/Provides (an) electrolyte(s). Used in Herbal Medicine as a sleep aid (during times of mental stress). Used in Herbal Medicine to help relieve restlessness and/or nervousness (calmative).
-Formulated with Chasteberry extract, clinically proven to help reduce the symptoms of PMS (Pre Menstrual Syndrome) such as mood changes and irritability; clinically showen to help reduce sweet or salt cravings. Includes all-natural l-theanine which helps to provide a temporary feeling of relaxation.

Health Canada safety notes

-Contraindication: Do not use if you are pregnant or breastfeeding.
-Contraindication: Do not take if you are pregnant or breast feeding.
-Contraindication: Do not use if you are allergic to plants of the Asteraceae/Compositae/Daisy family.

Official references

Health Canada LNHPD NPN:80141469 NPN:80142005 NPN:80056266 NPN:80042464

Health Canada licensing applies to specific products and is not a general endorsement of this supplement for every person or use.

PubMed evidence

Biomedical literature indexed in PubMed (NCBI) for this ingredient. Study counts reflect a keyword search, not an efficacy verdict.

21 PubMed studies

Studies indexed: 21
Top citations linked: 5
Last checked: May 13, 2026

Top cited studies

PubMed counts reflect a keyword search of the biomedical literature, not a curated efficacy verdict; results can include studies with mixed or negative findings.

US market label data

This ingredient appears in supplement product labels in the NIH Dietary Supplement Label Database.

NIH DSLD listed

Matched ingredient group: Theanine
Products on US market: 2,031
All marketed products: 3,136
Common forms: Capsule, Softgel Capsule

Common label amounts

-200 mg

Recognised synonyms

-2-amino-4-(ethylcarbamoyl)butyric acid
-alphawave l-theanine
-alphawave(tm)
-anti-cortisol amino acid complex
-gamma-ethylamino-l-glutamic acid

NIH DSLD reflects supplement product labels marketed in the US; a match indicates market presence, not a safety or efficacy endorsement.

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Sources10 sources

Health Canada LNHPD

Matched ingredient: L-Theanine. 1763 licensed product records.

Health Canada LNHPD(opens in new tab)
Health Canada LNHPD
Health Canada product licence NPN:80141469(opens in new tab)
Health Canada LNHPD · NPN:80141469
Health Canada product licence NPN:80142005(opens in new tab)
Health Canada LNHPD · NPN:80142005
Health Canada product licence NPN:80056266(opens in new tab)
Health Canada LNHPD · NPN:80056266
Health Canada product licence NPN:80042464(opens in new tab)
Health Canada LNHPD · NPN:80042464

PubMed (NCBI)

21 indexed studies. 5 top citations linked.

NIH DSLD

Matched group: Theanine. 2,031 products on the US market.

No NIH DSLD reference links recorded yet.

Evidence Level: MODERATE•Category: Mood Support

Last updated: 12/02/2026

Disclaimer: This information is for educational purposes only and should not replace professional medical advice. Always consult with a healthcare provider before starting any new supplement regimen.