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L-Theanine
Calm mind. Clear focus.
A daily 400 mg natural L-Theanine formula, delivered in two 200 mg capsules, for relaxation and mental clarity.
Calm and focus aren’t opposites.
L-Theanine is a naturally occurring, non-protein amino acid found in tea leaves, particularly green tea (Camellia sinensis). Unlike ingredients designed to stimulate or sedate, L-Theanine has been studied for something more balanced: a state often described as relaxed alertness — calmer, yet mentally present.
Human EEG research has shown that L-Theanine can influence alpha-band brain activity, which is associated with relaxed attention rather than drowsiness. More recent clinical research has also explored its effects on attention, acute stress and sleep, including studies using the 200 mg dose found in each Protokols capsule.
Protokols L-Theanine is deliberately focused. Each capsule provides 200 mg of natural L-Theanine from green tea extract standardised to 98% L-Theanine — a meaningful dose without turning the formula into a complicated “brain blend”.
Take it during demanding days when you want to feel calm without losing clarity, or make it part of an evening routine when the priority shifts from focus to unwinding. Research has investigated L-Theanine across both settings, with systematic reviews finding encouraging evidence around stress response, attention and sleep.
One focused ingredient. One clear purpose: calm when you need it, clarity when it matters.
Pure in purpose. Proven by research. Premium by design.
Nutritional Information
Ingredients: L-Theanine (98% natural Theanine from Green Tea Extract), Rice Flour (Oryza Sativa), Capsule Shell (Hydroxypropyl Methylcellulose)
2 capsules will provide:
| Active Nutrient | Amount per Serving | %NRV* |
|---|---|---|
| L-Theanine | 400 mg | ** |
*NRV = Nutritional Reference Value
**NRV not established
The studies below relate to the ingredient or nutrient form. Unless explicitly stated they are not trials of the finished Protokols product and do not guarantee an individual result.
01 — L-Theanine, Attention & Mental Performance
Systematic review & meta-analysis · 2026
One of the most comprehensive assessments of L-Theanine to date analysed 31 randomised controlled trials involving 1,168 participants.
The researchers found that a single 200 mg dose taken 30–60 minutes before cognitive testing significantly improved choice reaction time, supporting a short-term effect on attention in healthy adults.
Effects on acute stress were more modest and less certain, highlighting an important distinction between promising research and established outcomes.
Why it matters: The strongest recent evidence supports the idea at the heart of L-Theanine — calm does not have to come at the expense of mental clarity.
02 — 200 mg L-Theanine: Stress, Sleep & Cognitive Function
Randomised, double-blind, placebo-controlled crossover trial · 2019
Thirty healthy adults received 200 mg L-Theanine daily for four weeks or placebo.
Following L-Theanine supplementation, researchers reported improvements in measures relating to stress-related symptoms, sleep quality, verbal fluency and executive function. Sleep-related findings included improvements in measures of sleep latency and sleep disturbance.
Why it matters: This study investigated 200 mg L-Theanine daily, equivalent to the amount supplied by one Protokols capsule. Our recommended daily serving provides 400 mg across two capsules, so the study did not test our full daily serving.
03 — A Calming Response to Acute Stress
Randomised, triple-blind, placebo-controlled crossover trial · 2021
Healthy adults experiencing moderate stress received a single 200 mg dose of L-Theanine before completing an acute mental stress challenge.
Compared with placebo, L-Theanine produced greater increases in alpha brain-wave activity and greater reductions in salivary cortisol at selected time points. The researchers interpreted the increased alpha activity as consistent with a calming response.
Why it matters: Another controlled human study investigating a single 200 mg dose of L-Theanine, equivalent to the amount supplied by one Protokols capsule. Our recommended daily serving provides 400 mg across two capsules.
04 — L-Theanine & Attention
Double-blind, placebo-controlled crossover study · 2023
Researchers compared 100 mg, 200 mg and 400 mg L-Theanine with placebo in healthy adults.
The 200 mg dose significantly improved simple reaction time compared with placebo. The researchers found clearer benefits on simpler attention tasks than on more complex sustained-attention and inhibitory-control tasks.
Why it matters: Supports the use of L-Theanine for clear-headed attention, while also showing that the research does not justify claiming dramatic improvements across every aspect of cognition.
05 — L-Theanine & Sleep Quality
Systematic review & meta-analysis · 2025
Researchers reviewed 19 studies involving 897 participants, with 18 studies included in the meta-analysis.
L-Theanine supplementation was associated with statistically significant improvements in subjective sleep onset latency, daytime dysfunction and overall subjective sleep quality.
The authors also noted that more research using pure L-Theanine alone is needed to establish the optimal dose and duration.
Why it matters: The broader clinical evidence supports L-Theanine's potential as part of a relaxation and healthy-sleep routine, without positioning it as a sedative.
06 — Standalone L-Theanine & Healthy Sleep
Systematic review · 2026
A more recent systematic review specifically examined L-Theanine as a standalone intervention, identifying 13 trials involving 550 participants, including 11 randomised controlled trials.
Across doses ranging from 50–900 mg, the authors concluded that the available evidence suggests 200–450 mg per day may support healthy sleep in adults. Reported benefits included measures relating to sleep latency, maintenance, efficiency, sleep satisfaction and feelings of refreshment on waking.
Why it matters: The recommended Protokols daily serving of 400 mg falls within the 200–450 mg daily range highlighted by this review, providing a research-informed context for our two-capsule daily serving.
07 — Relaxation Without Drowsiness
Human EEG research · 2008
Researchers investigated L-Theanine using electroencephalography — EEG — to observe changes in brain activity.
Following 50 mg L-Theanine, participants demonstrated greater changes in alpha-frequency brain activity compared with placebo. Alpha activity is associated with a relaxed yet attentive mental state.
The researchers concluded that L-Theanine influenced mental alertness and arousal rather than behaving simply as a sedative.
Why it matters: This is part of the scientific basis behind L-Theanine's distinctive positioning: relaxation while remaining mentally present.
08 — Psychological & Physiological Stress Response
Double-blind human study · 2007
In a controlled laboratory study, participants completed a mental arithmetic task designed to produce acute stress.
L-Theanine was associated with reductions in heart-rate and salivary immune responses to the stress task compared with placebo. Analysis suggested the effect may have involved reduced sympathetic nervous-system activation.
Why it matters: An early controlled human study contributing to the scientific rationale for L-Theanine as a calm-focused ingredient during demanding situations.
Dosage
Take 2 capsules daily.
Serving
2 capsules provide 400 mg L-Theanine from green tea extract standardised to 98% natural L-Theanine.
Directions Take with food and water, or as directed by a healthcare professional.
Suitability
Suitable for vegetarians and vegans.
Free UK Delivery
Enjoy free standard UK delivery on every order.
14-Day First-Purchase Returns
Trying L-Theanine for the first time? You can request a return within 14 days of delivery, provided the product remains unopened, unused and in its original sealed packaging.
For return instructions, damaged orders and your statutory rights, please see our Returns & Refunds Policy.
Storage
Store in the original container in a cool, dry place, away from heat, moisture and direct sunlight. Keep tightly closed and do not refrigerate.
Best before end and batch number: See base of container.
Keep out of the sight and reach of young children.
Safety
Do not exceed the recommended daily dose. Food supplements should not be used as a substitute for a varied, balanced diet and healthy lifestyle.
If you are pregnant, breastfeeding, taking medication or have a medical condition, consult your doctor or pharmacist before use. This is particularly important if you take sleeping tablets, sedatives or other medicines that may cause drowsiness.
Do not use if you are allergic to any of the listed ingredients. Discontinue use and seek medical advice if you experience an adverse reaction.
Do not use if the safety seal is broken or missing.
PURE | PROVEN | PREMIUM
Realistic Expectations
If you are going to judge this product, judge it at twelve weeks, not at two.
Day 1
Weeks 1–4
Weeks 8–12
Ongoing
How we compare?
Which Protokols include this?
Restore Protokol
An evening routine designed to support calm, wind-down and better-quality rest.
Clarity Protokol
A daytime routine for calm focus, composure and clearer thinking.
Frequently Asked Questions (FAQs)
L-Theanine is a naturally occurring amino acid found primarily in tea leaves, especially green tea (Camellia sinensis). It has been studied for its effects on relaxation, attention, stress response and sleep.
Each Protokols capsule provides 200 mg of L-Theanine from 204.08 mg of green tea extract standardised to 98% natural L-Theanine.
The recommended daily serving is two capsules, providing 400 mg L-Theanine.
Because 200 mg is one of the most frequently studied doses in human clinical research on L-Theanine, including research on attention, acute stress, relaxation and sleep.
Each capsule provides this researched amount, with two capsules delivering our recommended daily serving of 400 mg L-Theanine.
We chose a meaningful, research-informed formula rather than simply chasing a larger number.
It depends on what you want from your routine.
During the day: Take 1 capsule when you want support for calm, clear-headed focus.
In the evening: Take 1 capsule 30–60 minutes before bed as part of your wind down routine.
Take a total of 2 capsules daily with water, providing 400 mg L-Theanine.
L-Theanine is not a sedative.
Its appeal is that it has been studied for promoting a more relaxed state while maintaining mental alertness, which is why many people use it during the day as well as in the evening.
Research suggests L-Theanine may support aspects of sleep quality, relaxation and sleep onset, but it should not be thought of as a sleeping pill.
Its role is more about helping create a calmer transition into rest rather than forcing sleep.
Yes. Protokols L-Theanine is formulated for daily use.
Take 2 capsules daily, providing 400 mg L-Theanine. One bottle contains 60 capsules, giving a 30-day supply.
Calm when you need it. Clarity when it matters.
Thoughtfully formulated supplements. Clear ingredients, considered routines, and wellbeing made simpler.