L-Theanine reduces psychological and physiological stress responses

L-Theanine reduces psychological and physiological stress responses by Kimura K, Ozeki M, Juneja LR, Ohira H.

The amino acid L-Theanine exhibited significant anti-stress activity in human subjects, researchers in Japan reported.

L-Theanine, which is found in green tea leaves and can be consumed in supplement form, is known to block the binding of L-glutamic acid to glutamate receptors in the brain, characteristics that suggest L-Theanine may influence psychological and physiological states under stress. To test this hypothesis, researchers conducted a clinical trial to determine how subjects consuming L-Theanine reacted to an acute stress task.

In the study, twelve subjects participated in four separate trials. In one trial they consumed L-theanine at the start of being exposed to the stressful experience, in another trial they consumed L-theanine midway through the stressful experience, a third trial where they consumed a placebo and a fourth trial where they consumed nothing.

The results showed that L-theanine intake resulted in a reduction in the heart rate and salivary immunoglobulin A (s-IgA) responses to an acute stress task compared to when the subjects were in the control groups. Furthermore, the analyses of heart rate variability indicated that the reductions in heart rate and s-IgA responses were likely attributable to a lessening of sympathetic nervous activation.

The researchers concluded, "the oral intake of L-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation."

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