Theanine-induced attenuation on mental stress-induced changes of the autonomic nervous balance in healthy young women

[Speaker] Taizo Kita:1
[Co-author] Nobuyuki Yanagihara:2, Noriaki Sato:3, Yukio Goto:2
1:Laboratory of Pharmacology, Faculty of Food and Nutrition, Kyushu Nutrition Welfare University, Japan, 2:Department of Pharmacology, School of Medicine, University of Occupational and Environmental Health, Japan, 3:Shared-Use Research Center, Facility for Education and Research Support, University of Occupational and Environmental Health, Japan

Theanine (L-theanine) is a major amino acid in green tea leaves, is thought to play neuroprotective role in the brain. The present study aimed to determine the attenuating effect of theanine on mental stress (arithmetic task)-induced changes in autonomic nervous balance (ANB) among healthy young women. The ANB of the women was assessed using a power spectral analysis of heart rate variability and a standard hexagonal radar chart. The Uchida-Kraepelin (an arithmetic task) for 15min (repeating four times) served as acute mental stressor. The ANB was measured before and after performing the task with ingestion of 200mg theanine or placebo. The excitability index significantly increased in the sympathetic nerves, indicating difference in the mean R-R interval between lying supine and standing upright and also the ratio of sympathetic: parasympathetic nerves areas (S/P) significantly increased in the participants after undergoing the mental stress task. The ingestion of theanine tended to increase the parameter of the mean R-R intervals in supine position as a parasympathetic parameter, and the S/P ratio significantly decreased in the participants after, compared with before the arithmetic task with ingested theanine. These results indicate that theanine significantly attenuated and improved mental stress-induced changes in ANB in healthy persons.

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