by Robert Goldman MD, PhD Iron Man Magazine
L-theanine is an amino acid found in tea leaves. Previous studies of dietary L-theanine supplements have suggested a therapeutic benefit in reducing stress, promoting relaxation and improving the quality of sleep. Akiko Higashiyama of the University of Shiga Prefecture in Japan and colleagues found that taking 200 milligrams per day of L-theanine helps people with anxiety focus on their daily activities.
The researchers recruited 18 healthy university students and assessed their anxiety levels using a standardized rating scale. 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 milligrams of L-theanine per 100 milliliters of water. The test was performed repeatedly, and assessments were done between 15 and 60 minutes after the subjects took the supplement.
The results showed that highly anxious students getting the L-theanine experienced a slowing of their heart rate, improved attentional performance and better reaction times compared to the highly anxious students who got a placebo. The students with minimal anxiety did not appear to get significant benefits. “The results demonstrate the significant enhanced activity of alpha bands, descending heart rate, elevated visual attentional performance and improved reaction time response among high-anxiety-propensity subjects compared to a placebo,” the researchers wrote. “Results evidently demonstrated that L-theanine clearly has a pronounced effect on attention performance and reaction time response in normal healthy subjects prone to have high anxiety.”
Higashiyama, et al. (2011). Effects of L-theanine on attention and reaction time response. Journal of Functional Foods. April 19.
—Dr. Bob Goldman
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