The Effects of L-theanine Containing Functional Beverage on Mental Relaxation and Fatigue Perception

Song, Chan Hee; Chung, Kyoo In; Song, Sang Wook; Kim, Kyung Soo

Abstract

BACKGROUND
L-theanine is one of the most popular amino acids in green tea and has been known to produce mental relaxation, lower blood pressure and improve learning ability in human beings. But, few studies on these effects for human beings have been conducted so far. This study was conducted to evaluate the effect of L-theanine containing functional beverage on mental relaxation and fatigue perception. METHODS: Twenty healthy volunteers aged 30 to 55 years those who has had persistent fatigue for more than 1 month without any specific disease were recruited through written advertisement. All the subjects gave their informed consent, and the study was approved by Institutional Review Board of St. Mary's Hospital. This study was performed in a randomized placebo controlled double blind cross over fashion. Pathologic fatigue due to disease state was screened through medical history, physical examination, laboratory tests and questionnaires. alpha to beta power value of EEG as a surrogate marker of mental relaxation was measured in frontal and occipital regions for an hour after administration of placebo or test (200 mg L-theanine) solutions and crossed over at 7-day intervals. We analyzed average alpha to beta power value of EEG in frontal and occipital regions at 10 minute intervals for each 5 minutes. The baseline and 7-day follow-up scores of fatigue severity scale (FSS) were also evaluated. RESULTS: Repeated ANOVA revealed that there were significant differences of frontal alpha to beta power value between placebo and test in high anxiety group (P<0.01). The mean values at 15, 25, 35, 45, and 55 minute intervals were 0.57, 0.48, 0.52, 0.66, and 0.61 in placebo, respectively, and 0.73, 0.82, 0.78, 0.91, and 0.97 in test, respectively. But there were no significant differences of frontal alpha to beta power value between placebo and test groups with low anxiety (P>0.05). Fatigue score was significantly decreased in test (P<0.05), but not in placebo (P>0.05) after 7-day administration of placebo or test solutions. The mean differences from baseline in placebo and test were 0.42, and 0.80, respectively. CONCLUSIONS:The results of this study suggest that L-theanine containing functional beverage should promote alpha to beta power value in relation to mental relaxation, and also have the effect of reducing the fatigue perception.