L-theanine
Capsule
Moderate
Some good studies, not many repeats
Moderate: several small RCTs and a systematic review agree on acute stress reduction; sleep data limited to one 4-week RCT.
Stressed adults taking 200 mg a day for four weeks fell asleep faster and woke up less. Taken in the day it takes the edge off stress without making you drowsy.
L-theanine, the calming amino acid in green tea, lowered stress-related sleep disturbance and sleep latency over four weeks at 200 mg and blunts acute stress arousal within an hour — without sedation. It's a gentle daytime tool more than a sleep drug.
Raises GABA, serotonin and dopamine, increases alpha-wave activity; crosses the blood–brain barrier within 30–60 minutes.
Stress-driven poor sleep; caffeine users (pairs with coffee to remove the jitters). Very safe.
What to buy
- ✓200 mg per capsule
- ✓Suntheanine® or ≥98% pure L-theanine
- ✕Blends with high caffeine if you want it for sleep
- · Very safe; additive with antihypertensives.
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The dose used in the 4-week sleep trial.
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The classic pairing: theanine takes the edge off caffeine's jitter without cancelling the alertness. Only useful if you are already taking caffeine — otherwise take theanine alone.
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See all on AmazonEvery result, next to the line that means no effect
Each diamond is a study's best estimate. The thin line shows how sure the study was: the shorter the line, the more certain the result.
- Pittsburgh sleep-disturbance subscorepts · Hidese 2019−0.50[not given]
Each unit gets its own scale, so numbers are never mixed on one line. When a study gave no range, we leave it blank instead of inventing one.
2 studies over 1 years
The studies
- 1.Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trialNutrients · 2019 · rct · n = 30
200 mg/day for 4 weeks improved sleep latency, sleep disturbance and reduced sleep-medication use.
- 2.The effects of green tea amino acid L-theanine consumption on the ability to manage stress and anxiety levels: a systematic reviewPlant Foods for Human Nutrition · 2019 · systematic review
200–400 mg reduces stress and anxiety under acute stressors.
Umbral is a wellness product, not a medical device. It does not diagnose, treat, cure or prevent any disease. Supplement information is educational; talk to a clinician before starting anything, especially if you are pregnant, under 18, managing a condition or taking medication.
These statements have not been evaluated by the Food and Drug Administration.