L-theanine
From the YapSpan Longevity Wiki · Updated 2026-09-28
L-theanine is an amino acid (a building block of protein) found in tea leaves; as a supplement it is studied for stress, relaxation and self-reported sleep quality.
Educational only, not a recommendation to take anything. YapSpan estimates are for reflection and entertainment only. They are not medical advice, a diagnosis, or a prediction of any individual outcome. Check with a doctor before making any medical decision.
L-theanine (gamma-glutamylethylamide) is a non-protein amino acid found in the tea plant, Camellia sinensis; a cup of black tea contains about 20 mg [1]. It is structurally similar to glutamate and is proposed to modulate glutamate receptor signalling. Electroencephalography (EEG) studies show increased activity in the alpha frequency band, a pattern associated with relaxed wakefulness without drowsiness. In a placebo-controlled EEG study of healthy young adults resting with eyes closed, 50 mg of L-theanine (16 participants) produced a greater increase in alpha activity over the 45 to 105 minutes after ingestion than placebo (19 participants) [1]. It is not classed as a hypnotic, and its proposed relevance to sleep is through reduced stress-related arousal before sleep.
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YapSpan estimates are for reflection and entertainment only. They are not medical advice, a diagnosis, or a prediction of any individual outcome. Check with a doctor before making any medical decision.