On the other hand, people with minimal anxiety levels did not experience any benefits from supplementation, according to findings published in the Journal of Functional Foods.
“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.”
The study used Taiyo Kagaku’s Suntheanine-branded L-theanine ingredient, and the Japanese company funded the study.
Relax and focus
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 2 percent), which means that effective dosage levels (of 100 – 200mg/day) cannot be delivered from drinking tea.
Various health effects have been associated with L-theanine, including relaxation, neuroprotective effects, and improved attention.
During rest, L-theanine increases alpha activity in EEG models - suggesting greater relaxation. Whilst 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 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).
Student 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 student with minimal anxiety.
“It is noteworthy to mention that unlike other conventional anti-anxiety treatments, L-theanine did not result in increased drowsiness, slowed reflexes, or impaired concentration,” wrote the authors.
“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.”
Source: Journal of Functional Foods
Published online ahead of print, doi: 10.1016/j.jff.2011.03.009
“Effects of L-theanine on attention and reaction time response”
Authors: A. Higashiyama, H.H. Htay, M. Ozeki, L.R. Juneja, M.P. Kapoor