L-Theanine
L-Theanine
L-Theanine is a non-proteinogenic amino acid found naturally in green tea (Camellia sinensis) that promotes relaxation without sedation. It is primarily used to reduce stress and anxiety, improve focus and attention, and enhance the quality of sleep, often combined with caffeine to optimize cognitive performance.
Mechanism of Action
L-Theanine increases brain levels of GABA, serotonin, and dopamine while modulating glutamate activity by acting as an antagonist at NMDA and AMPA receptors, producing anxiolytic and neuroprotective effects. It also promotes alpha-wave brain activity (8-12 Hz), a state associated with calm alertness, as demonstrated by EEG studies. When combined with caffeine, it attenuates caffeine-induced sympathetic nervous system arousal while preserving or enhancing its pro-cognitive effects.
Evidence by Health Goal(18 goals)
Dosing Protocols
Morning with or without food; a second dose may be taken in early afternoon
For cognitive synergy, pair with caffeine at a 2:1 ratio (e.g., 200mg L-Theanine : 100mg caffeine). For sleep support, take 200mg 30-60 minutes before bed. Doses above 400mg/day show diminishing returns in most individuals.
Safety & Side Effects
L-Theanine has an excellent safety profile and is classified as Generally Recognized As Safe (GRAS) by the FDA; it is well-tolerated at doses up to 400mg/day in healthy adults with no significant toxicity identified in clinical trials. Caution is warranted in individuals with low blood pressure or those taking antihypertensive medications, CNS depressants, or stimulants, as interactions can occur.
Possible Side Effects
- !Headache at higher doses (>400mg), likely from glutamate modulation
- !Mild drowsiness or sedation, particularly at doses above 200mg
- !Gastrointestinal discomfort (nausea, loose stools) at high doses in sensitive individuals
- !Hypotension (low blood pressure) at higher doses due to vasodilatory effects
- !Dizziness in individuals sensitive to blood pressure changes
- !Irritability or rebound anxiety upon abrupt discontinuation after prolonged high-dose use (rare)
Interactions
- -May potentiate CNS depressants (benzodiazepines, alcohol, sleep aids) — additive sedative effects possible
- -Can lower blood pressure — use caution with antihypertensive medications and monitor for hypotension
- -Synergistic cognitive effects with caffeine — beneficial interaction but may alter perceived stimulant response
- -May enhance the anxiolytic effects of other GABAergic supplements (e.g., ashwagandha, valerian root) — monitor for excessive sedation
- -Theoretical interference with stimulant medications (e.g., Adderall, Ritalin) by blunting their sympathomimetic effects
Cost & Where to Buy
Widely available as an over-the-counter supplement. Bulk powder is cheapest; branded capsules (e.g., Suntheanine, a patented pharmaceutical-grade form) cost more but offer verified purity and bioavailability. Monthly cost based on 200mg/day dosing.
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