Evidence supporting the use of: L-theanine
For the health condition: Tension

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Synopsis

Source of validity: Scientific
Rating (out of 5): 3

L-theanine is an amino acid primarily found in tea leaves, especially green tea. Its use to support relief from tension—characterized by mental or physical stress and anxiety—has scientific backing, though the overall evidence quality is moderate rather than robust. Several randomized, placebo-controlled trials have shown that L-theanine supplementation can promote relaxation and reduce subjective experiences of stress and tension without causing drowsiness. Mechanistically, L-theanine is believed to increase alpha brain wave activity, associated with a state of "relaxed alertness." In addition, it may modulate neurotransmitter levels, including GABA, dopamine, and serotonin, contributing to its calming effects.

A 2019 systematic review in Phytotherapy Research concluded that L-theanine supplementation (typically 200-400 mg/day) offers potential benefits for stress and anxiety reduction in both healthy and clinical populations. However, most studies are small, short-term, and sometimes funded by supplement manufacturers, which can introduce bias. Nevertheless, subjective reports from both clinical trials and traditional use (as part of green tea consumption) support its tension-reducing effects. Importantly, L-theanine is considered safe and well-tolerated at commonly used doses.

In summary, while more large-scale, long-term studies are needed, there is scientific support for the use of L-theanine in managing mild tension and stress. It is a popular ingredient in dietary supplements targeting relaxation and mental well-being.

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