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HealthVetted
Sleep · Ingredient

L-theanine

BModerate evidenceHow we grade evidence
Research snapshot2sources cited2019–2025evidence window

What it is

Amino acid from tea that promotes relaxation by increasing alpha brain-wave activity and modulating GABA, dopamine, and serotonin without sedation.

What the evidence says

Better characterized for relaxation/anxiety than for sleep itself. In a small placebo-controlled RCT (30 healthy adults), 200 mg/day for 4 weeks lowered PSQI sleep scores and anxiety/depression measures, with improvements in sleep latency and sleep-disturbance subscales. A 2025 systematic review (19 trials, ~897 participants) found mainly subjective improvements in sleep latency and daytime dysfunction. Effects are modest, and many positive trials combine L-theanine with casein peptides or other actives.

Typical dose in trials

200 mg/day (range ~200-400 mg), often taken in the evening.

Educational summary of doses studied — not a recommendation. Talk to a clinician before starting any supplement.

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Sources (2)

  1. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial — Nutrients (2019)
  2. Examining the effect of L-theanine on sleep: a systematic review of dietary supplementation trials — Nutritional Neuroscience (2025)
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Educational summary of published research, checked against primary sources and linked inline. Not medical advice; supplements are not FDA-evaluated to treat disease. See our editorial policy.