Promotes Relaxation and Stress Reduction*

L-theanine

L-Theanine is an amino acid found in tea leaves. It is able to cross the blood-brain barrier, where it augments sleep architecture and promotes relaxation and stress reduction.

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What is it and how does promote it help promote relaxation

L-theanine

L-Theanine is an amino acid found in tea leaves that is also available as an over-the-counter supplement. It is able to cross the blood-brain barrier, where it augments sleep architecture and promotes relaxation and stress reduction1,2,3.

It is thought that L-theanine may promote sleep through modulation of neurotransmitter signals important for the sleep-wake cycle. In general, excitatory signaling by molecules like glutamate promote wakefulness, while inhibitory signals via GABA or glycine promote sleep4.

L-theanine is structurally similar to glutamic acid, and as a result, its psychoactive effects have been compared to the effects of glutamate. In animal models, L-theanine administration dampened excitatory signaling by blocking two major glutamate receptors, while also enhancing inhibitory signaling via increased glycine production5,6. This net increase in inhibitory activity theoretically should promote sleep, and preliminary evidence in a small placebo-controlled clinical trial support this assertion. In boys with attention deficit hyperactivity disorder (ADHD), L-theanine administration over six weeks significantly improved sleep efficiency and decreased nocturnal sleep activity7. Notably, L-theanine was non-sedating in this or other studies8,9.

Separately, L-theanine has been shown to facilitate beneficial emotional processing. Some supporting evidence comes from studies investigating the effects of L-theanine on brain activity, given the known association between specific frequencies detected on EEG and affective states. Alpha waves, which reflect a conscious but relaxed state, are enhanced after administration of L-theanine in both healthy and anxious individuals. These effects were shown to be dose-dependent and correlate with subjective improvement in relaxation as well10,11.

Additionally, a systematic review of five placebo-controlled clinical trials indicated that L-theanine consistently reduced subjective reports of stress and anxiety in a healthy adult population12. Complementary findings were demonstrated in a laboratory-based, small placebo-controlled trial, in which L-theanine depressed physiologic markers of stress and sympathetic outflow in response to an acute stress task13.

Though safety of L-theanine has not been studied extensively in humans, clinical trials in which high total daily doses of L-theanine (400mg) were administered did not report any significant adverse effects14.