L-Theanine
A 2026 meta-analysis of 31 RCTs (n=1,168) found a single 200mg dose taken 30–60 minutes before testing improved choice reaction time; its acute stress effect was modest and driven by high-risk-of-bias studies, and anxiety effects were inconsistent. With caffeine, an 11-study meta-analysis (Camfield 2014) found moderate effects versus placebo on alertness and attention-switching accuracy; Kahathuduwa 2016 found additive effects with no interaction, and Foxe 2012 found no added benefit over either compound alone. The one alpha-wave (MEG) trial found higher alpha activity at 2 hours, and only in people with higher trait anxiety.
Evidencia revisada el
Mecanismo de acción
L-theanine is a non-protein amino acid found primarily in green tea. It crosses the blood-brain barrier and has been linked to increased alpha brain wave activity. It also modulates GABA, serotonin, and dopamine levels. Combined with caffeine, it improved attention measures versus placebo in several trials, though Foxe 2012 found no added benefit over either compound alone.
Resumen de evidencia clínica
A 2026 meta-analysis of 31 RCTs (n=1,168) found a single 200mg dose taken 30–60 minutes before testing improved choice reaction time; its acute stress effect was modest and driven by high-risk-of-bias studies, and anxiety effects were inconsistent. With caffeine, an 11-study meta-analysis (Camfield 2014) found moderate effects versus placebo on alertness and attention-switching accuracy; Kahathuduwa 2016 found additive effects with no interaction, and Foxe 2012 found no added benefit over either compound alone. The one alpha-wave (MEG) trial found higher alpha activity at 2 hours, and only in people with higher trait anxiety.
Matriz de efectos en humanos
Basado solo en ensayos clínicos en humanos. Se excluyen los datos en animales e in vitro.
| Efecto | Evidencia | Magnitud | Estudios |
|---|---|---|---|
| Calm Focus (Alpha Waves) | preliminar | Pequeño | 1 |
| Anxiety & Stress | mixta | Pequeño | 2 |
| Sleep Quality | moderada | Pequeño | 1 |
| With Caffeine | moderada | Moderado | 4 |
Clave de evidencia: Sólida = varios ECA consistentes · Moderada = ECA más pequeños o menos numerosos · Preliminar = ensayos iniciales o n pequeño · Mixta = resultados contradictorios
Beneficios documentados
- Faster reaction time after a single 200mg dose
- Better attention with caffeine than with placebo in several trials
- Small improvements in subjective sleep quality
Efectos secundarios y precauciones
- Extremely well tolerated — no serious adverse events across a 31-RCT meta-analysis
- Possible mild sedation at high doses
- Generally considered very safe
Cómo tomarlo
Recomendaciones de combinación
Ingredientes que se combinan bien con L-Theanine y por qué.
The trials we cite used 50–250mg theanine with 40–250mg caffeine. Versus placebo, the combination improved attention measures in several trials, though Foxe 2012 found no added benefit over either compound alone; in a controlled trial (Rogers 2008) theanine did not significantly reduce caffeine jitteriness.
Both have anxiolytic properties working via different mechanisms. L-Theanine provides immediate calm; Bacopa builds sustained stress tolerance over weeks. A gentle, non-sedating anxiety-reduction combination.
Both target stress through distinct pathways (GABA modulation for theanine; HPA axis for ashwagandha). Good daytime anxiety stack without sedation.
Preguntas frecuentes
What is the ideal ratio of L-Theanine to caffeine?
No trial has established an ideal ratio. The positive combination trials used 97–250mg theanine with 40–160mg caffeine — for example 100mg theanine with 50mg caffeine (Owen 2008), 250mg with 150mg (Haskell 2007) and 200mg with 160mg (Kahathuduwa 2016). A meta-analysis found the caffeine dose drove the effect more than the theanine dose.
Does L-Theanine work without caffeine?
Partly. On its own, a single 200mg dose improved choice reaction time in a 2026 meta-analysis of 31 RCTs, but anxiety effects were inconsistent and the one alpha-wave trial found an effect only in people with higher trait anxiety. It's not stimulating on its own.
Is it safe to take L-Theanine every day?
Yes. Green tea contains theanine and has been consumed daily for millennia without toxicity concerns. No tolerance develops. Chronic daily use is both safe and effective. No cycling required.
Why take a supplement when I can just drink green tea?
A standard cup of green tea contains ~25–50mg of L-Theanine — well below the 100–200mg therapeutic dose. You would need 4–8 cups of green tea to match a single supplement dose, along with a significant caffeine load. Supplements allow precise dosing without unwanted caffeine.
Can L-Theanine help with sleep if taken at night?
Modestly. A 2025 meta-analysis (18 studies, n=897) found small improvements in subjective sleep onset latency, daytime dysfunction and overall sleep quality. It doesn't cause sedation. Combinations with magnesium are popular but have not been tested in a trial.
Principales stacks que contienen L-Theanine
L-Theanine en América Latina
Productos disponibles en América Latina
ANVISA / COFEPRIS / INVIMA
Nota regulatoria
Esta página es contenido editorial con fines educativos y no constituye consejo médico. Los suplementos alimenticios están regulados por agencias nacionales: la Agência Nacional de Vigilância Sanitária (ANVISA) en Brasil bajo RDC 243/2018, la Comisión Federal para la Protección contra Riesgos Sanitarios (COFEPRIS) en México, y el Instituto Nacional de Vigilancia de Medicamentos y Alimentos (INVIMA) en Colombia. En Argentina, la Disposición 2105/2022 de la Administración Nacional de Medicamentos, Alimentos y Tecnología Médica (ANMAT) prohíbe siete productos concretos de las marcas Newmind y PURENOOTROPICS (Noopept, F-Phenibut y Bacopa) — no recomendamos productos con Noopept ni F-Phenibut a lectores en Argentina. Aviso para lectores en Brasil: el 2 de julio de 2026, ANVISA informó que algunos péptidos inyectables promocionados en internet, entre ellos GHK-Cu, BPC-157, TB-500, CJC-1295 e ipamorelin, no están regularizados en ninguna categoría (alimento, medicamento, cosmético ni suplemento alimentario) y son ilegales para cualquier uso en salud, incluido el estético. No enlazamos ni recomendamos proveedores que realicen envíos de formulaciones inyectables a Brasil. Consulte siempre a un profesional de la salud calificado antes de comenzar cualquier suplemento. / This page is editorial and not medical advice. Supplements are regulated by national agencies: the Agência Nacional de Vigilância Sanitária (ANVISA) in Brazil, the Comisión Federal para la Protección contra Riesgos Sanitarios (COFEPRIS) in Mexico, and the Instituto Nacional de Vigilancia de Medicamentos y Alimentos (INVIMA) in Colombia. In Argentina, ANMAT Disposition 2105/2022 prohibits seven specific products of the Newmind and PURENOOTROPICS brands (Noopept, F-Phenibut and Bacopa) — we do not recommend products containing Noopept or F-Phenibut to Argentine readers. Brazil notice: on 2 July 2026, ANVISA stated that some injectable peptides promoted online, including GHK-Cu, BPC-157, TB-500, CJC-1295 and ipamorelin, are not regularised in any category (food, medicine, cosmetic or food supplement) and are illegal for any health use, including aesthetic use. We do not link to or recommend vendors that ship injectable formulations to Brazil. Consult a qualified healthcare professional before starting any supplement.
Fuentes (11)ampliar
- PMID 42410082Cognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials (2026)
- PMID 24946991Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis (2014)
- PMID 18006208The effects of L-theanine, caffeine and their combination on cognition and mood (2007)
- PMID 26869148Acute effects of theanine, caffeine and theanine-caffeine combination on attention (2016)
- PMID 26797633Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial (2016)
- PMID 40056718The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis (2025)
- PMID 17891480Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. (2008)
- PMID 18681988The combined effects of L-theanine and caffeine on cognitive performance and mood. (2008)
- PMID 21040626The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. (2010)
- PMID 22326943Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task. (2012)
- PMID 25761837A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood. (2015)