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Nutrients
Volume 9
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10.3390/nu9070777
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Article

Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content

by
Keiko Unno
1,2,*,
Shigenori Noda
3,
Yohei Kawasaki
3,
Hiroshi Yamada
3,
Akio Morita
4,
Kazuaki Iguchi
1 and
Yoriyuki Nakamura
2
1
Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan
2
Tea Science Center, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
3
Division of Drug Evaluation & Informatics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
4
Department of Functional Plant Physiology, Faculty of Agriculture, Shizuoka University, Shizuoka 422-8529, Japan
*
Author to whom correspondence should be addressed.
Nutrients 2017, 9(7), 777; https://doi.org/10.3390/nu9070777
Submission received: 10 June 2017 / Revised: 11 July 2017 / Accepted: 16 July 2017 / Published: 19 July 2017
(This article belongs to the Special Issue Effects of Polyphenol-Rich Foods on Human Health)
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Abstract

Caffeine, one of the main components in green tea, can interfere with sleep and block the effect of theanine. Since theanine, the main amino acid in tea leaves, has significant anti-stress effects in animals and humans, we examined the effects of green tea with lowered caffeine content, i.e., low-caffeine green tea (LCGT), on stress and quality of sleep of middle–aged individuals (n = 20, mean age 51.3 ± 6.7 years) in a double-blind crossover design. Standard green tea (SGT) was used as the control. These teas (≥300 mL/day), which were eluted with room temperature water, were consumed over a period of seven days after a single washout term. The level of salivary α-amylase activity (sAA), a stress marker, was significantly lower in participants that consumed LCGT (64.7 U/mL) than in those that consumed SGT (73.9 U/mL). Sleep quality was higher in participants that consumed a larger quantity of LCGT. In addition, a self-diagnostic check for accumulated fatigue was significantly lower in those participants that consumed LCGT than SGT. These results indicate that LCGT intake can reduce stress in middle-aged individuals and improve their quality of sleep. The reduction in caffeine is suggested to be a valid reason for enhancing the anti-stress effect of green tea.
Keywords: anti-stress effect; caffeine; green tea; middle-aged individuals; salivary α-amylase; sleep anti-stress effect; caffeine; green tea; middle-aged individuals; salivary α-amylase; sleep
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MDPI and ACS Style

Unno, K.; Noda, S.; Kawasaki, Y.; Yamada, H.; Morita, A.; Iguchi, K.; Nakamura, Y. Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content. Nutrients 2017, 9, 777. https://doi.org/10.3390/nu9070777

AMA Style

Unno K, Noda S, Kawasaki Y, Yamada H, Morita A, Iguchi K, Nakamura Y. Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content. Nutrients. 2017; 9(7):777. https://doi.org/10.3390/nu9070777

Chicago/Turabian Style

Unno, Keiko, Shigenori Noda, Yohei Kawasaki, Hiroshi Yamada, Akio Morita, Kazuaki Iguchi, and Yoriyuki Nakamura. 2017. "Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content" Nutrients 9, no. 7: 777. https://doi.org/10.3390/nu9070777

APA Style

Unno, K., Noda, S., Kawasaki, Y., Yamada, H., Morita, A., Iguchi, K., & Nakamura, Y. (2017). Reduced Stress and Improved Sleep Quality Caused by Green Tea Are Associated with a Reduced Caffeine Content. Nutrients, 9(7), 777. https://doi.org/10.3390/nu9070777

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