L-Theanine
Also known as: Theanine, Suntheanine®
The calming amino acid in green tea — promotes relaxed focus without sedation, and enhances the benefits of caffeine.
What it is
L-Theanine is a naturally occurring amino acid found almost exclusively in tea (Camellia sinensis) and the Bay Bolete mushroom. It is responsible for the calm, focused mental state associated with green tea consumption — the counterbalance to caffeine's stimulating effects. Clinical research consistently demonstrates anxiolytic and cognitive-enhancing effects, particularly when combined with caffeine.
How it works
Theanine crosses the blood-brain barrier and increases activity of GABA, serotonin, and dopamine neurotransmitters. It also increases alpha brain wave activity (associated with wakeful relaxation) and reduces beta wave activity (associated with anxiety and hyperarousal). When combined with caffeine, theanine attenuates caffeine's negative effects (jitteriness, anxiety, blood pressure spike) while enhancing its positive effects (focus, attention, reaction time).
Clinical dose range
100–400 mg/day
Most cognitive performance studies use 100–200 mg. The optimal caffeine:theanine ratio studied is 1:2 (e.g., 100 mg caffeine + 200 mg theanine). For sleep support and anxiety reduction, 200–400 mg in the evening is commonly used. Non-habit-forming — can be taken daily without tolerance development.
Forms comparison
What to look for on the label
- Specifies L-Theanine (not DL-theanine, which includes the biologically inactive D-isomer)
- Suntheanine® branded ingredient preferred
- Third-party tested for identity and potency
- Dose 100–200 mg per serving
Health goals supported
Safety & dosing notes
Excellent safety profile. No established UL. Non-sedating at 100–200 mg. Larger doses (400+ mg) may cause mild drowsiness in some individuals. No known drug interactions at typical doses. Generally considered one of the safest supplements available.
SuppsBuddy awards a high form score to Suntheanine® and pharmaceutical-grade L-theanine. Products combining theanine with caffeine receive a formulation quality bonus for their synergistic ratio. D-theanine or unspecified isomers receive reduced scores.
Frequently asked questions
What is L-Theanine?
L-Theanine is a naturally occurring amino acid found almost exclusively in tea (Camellia sinensis) and the Bay Bolete mushroom. It is responsible for the calm, focused mental state associated with green tea consumption — the counterbalance to caffeine's stimulating effects. Clinical research consistently demonstrates anxiolytic and cognitive-enhancing effects, particularly when combined with caffeine.
How does L-Theanine work?
Theanine crosses the blood-brain barrier and increases activity of GABA, serotonin, and dopamine neurotransmitters. It also increases alpha brain wave activity (associated with wakeful relaxation) and reduces beta wave activity (associated with anxiety and hyperarousal). When combined with caffeine, theanine attenuates caffeine's negative effects (jitteriness, anxiety, blood pressure spike) while enhancing its positive effects (focus, attention, reaction time).
What is the typical clinical dose range for L-Theanine?
100–400 mg/day. Most cognitive performance studies use 100–200 mg. The optimal caffeine:theanine ratio studied is 1:2 (e.g., 100 mg caffeine + 200 mg theanine). For sleep support and anxiety reduction, 200–400 mg in the evening is commonly used. Non-habit-forming — can be taken daily without tolerance development.
What forms of L-Theanine should I look for?
Suntheanine® (pure L-isomer): Patented enzymatic process producing 100% L-theanine isomer; most clinically studied form | L-Theanine (pharmaceutical grade): Pure L-isomer; biologically active form | Green tea extract (theanine-standardized): Natural source; lower theanine concentration per serving
Is L-Theanine safe?
Excellent safety profile. No established UL. Non-sedating at 100–200 mg. Larger doses (400+ mg) may cause mild drowsiness in some individuals. No known drug interactions at typical doses. Generally considered one of the safest supplements available. This information is educational and is not medical advice.
How does SuppsBuddy evaluate L-Theanine?
SuppsBuddy awards a high form score to Suntheanine® and pharmaceutical-grade L-theanine. Products combining theanine with caffeine receive a formulation quality bonus for their synergistic ratio. D-theanine or unspecified isomers receive reduced scores.
Related ingredients
This page is for educational purposes only. These statements have not been evaluated by the FDA. This information is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional before starting any supplement.