Can L-Theanine Cause Anxiety?

L-Theanine is a supplement mainly used to reduce stress, anxiety, and promote sleep. Another scientific name for theanine powder is gamma-glutamylethylamide, which is one of the major amino acid components in green and black tea.

L-theanine is considered to be the substance that is responsible for the green tea’s taste. Though little research regarding the L-theanine supplementation has been done in humans, there’s no clear idea of benefits or side effects. However, several studies in humans proved that L-theanine reduces stress and anxiety. The supplement blocks the binding of L-glutamic acid to glutamate receptors in the brain. Those taking bulk L-theanine have more alpha-brain wave activity in the brain, which is the index of enhanced relaxation.

According to a publication in the Biological Psychology journal in August 2006, L-theanine has proved to reduce psychological and physiological stress responses. (Biol Psychol. 2006 Aug 21; Nagoya University Department of Psychology, Nagoya, 464-8601, Japan). The results of this study showed that the intake of L-theanine resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task relative to the placebo control condition.

In addition, by analyzing heart rate variability, the researches proved that the reductions in HR and s-IgA were likely attributable to an attenuation of sympathetic nervous activation. The suggestion was made that through the inhibition of cortical neuron excitation, the oral intake of L-theanine could cause anti-stress and anti-anxiety effects.