L-theanine May Boost Attention for Anxious Folks
Lee Swanson Research Update
"Given that L-theanine is a relaxant, it is directly or indirectly involved at the neurochemical level and thus it is impacted by a number of neurotransmitter systems," wrote the scientists from the University of Shiga Prefecture and Taiyo Kagaku.
"Therefore, 200 mg of L-theanine intake may help normal people with high anxiety propensity to concentrate on their daily activities."
L-theanine, an amino acid found in tea leaves, is thought to help reduce stress, promote relaxation and improve the quality of sleep. L-theanine is found in tea leaves in low concentrations (less than two percent), which means that effective dosage levels (of 100-200 mg/day) cannot be delivered from drinking tea.
During rest, L-theanine increases alpha activity in EEG models—suggesting greater relaxation. The amino acid is known to induce changes in alpha activity that indicates increased attentional processing during tasks that require attention.
The new study confirmed the dose of 200 mg for "enhanced performance in a visual attention task, and reaction time response, among the subjects with higher anxiety propensity symptoms."
The Japanese researchers recruited 18 healthy university students and assessed their anxiety levels using the manifest anxiety scale (MAS).
Students with high anxiety were put in one group, while students with minimal anxiety were put in another group. Both groups received water or water plus 200 mg of L-theanine per 100 ml of water. The test was performed repeatedly and assessments performed between 15 and 60 minutes after ingestion.
Results showed that highly anxious students receiving the L-theanine displayed a slowing of their heart rate, improved attentional performance and better reaction times, compared to members of the same group receiving placebo. No significant benefits were observed in the students with minimal anxiety.
"Results of a present study showed that ingestion of 200 mg of L-theanine changes the electrical activity in the brain by increasing alpha electric band measured by EEG," the authors wrote.
Journal of Functional Foods; Published online ahead of print.
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May 2011