著者

Keiko Unno

出版者

The Japanese Society of Physical Fitness and Sports Medicine

雑誌

The Journal of Physical Fitness and Sports Medicine (ISSN:21868131)

巻号頁・発行日

vol.5, no.2, pp.117-122, 2016-05-25 (Released:2016-05-14)

参考文献数

53

被引用文献数

4 10

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Since aging is the most important risk factor for dementia, measures to slow the onset of brain aging are an important strategy for preventing dementia. Accumulation of oxidative damage is considered to be a major cause of aging. Catechins in green tea (GTCs) have powerful antioxidative activity. Ingestion of GTCs suppressed oxidative damage, brain atrophy and cognitive decline in aged mice. Age-related cognitive decline was significantly suppressed in mice when middle-aged mice started to drink green tea catechins. Middle-aged people are thus expected to be able to suppress brain aging by ingestion of GTCs. In addition, numerous people are stressed under various conditions. Brain aging was accelerated and lifespan shortened in experimental animals that were chronically and psychosocially stressed. Theanine, an amino acid in green tea, suppressed stress-induced aging. However, the anti-stress effect of theanine is blocked by catechins and caffeine that are main components in green tea. Daily drinking of several cups of green tea is considered to suppress brain aging. In addition, theanine-rich green tea or green tea with a lowered level of caffeine is expected to suppress stress and stress-induced aging.

著者

Daisuke FURUSHIMA Ibuki SUGIYAMA Yuzuki NOMURA Keiko UNNO Hiroshi YAMADA

出版者

Center for Academic Publications Japan

雑誌

Journal of Nutritional Science and Vitaminology (ISSN:03014800)

巻号頁・発行日

vol.68, no.6, pp.540-546, 2022-12-31 (Released:2022-12-31)

参考文献数

30

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l-Theanine, the most abundant amino acid component in green tea, has anti-stress effects and refreshes the mental state. A recent study demonstrated that l-arginine, the second most abundant amino acid in green tea, might enhance the anti-stress effects of l-theanine. The aim of this study was to evaluated the effects of combined ingestion of l-theanine and l-arginine on psychological stress in humans. A randomized placebo-controlled trial was conducted including 120 healthy young adults (mean age 22.4 y, 63.3% female). Subjects were randomly assigned to theanine (200 mg l-theanine), combined theanine/arginine (200 mg l-theanine, 50 mg l-arginine), or placebo groups. After consuming a test beverage, we administered a stress-loading test (Uchida-Kraepelin performance test) and performed salivary alpha-amylase activity (sAA) measurements to assess the physiological stress response at 0 min (immediately after), 5 min, and 15 min. The changes in sAA at 15 min after the stress-loading test were −2.75 (11.2) kIU/L in the theanine/arginine group, −0.40 (11.5) kIU/L in the theanine group, and 6.95 (18.6) kIU/L in the placebo group. The values in the theanine/arginine (p=0.007) and theanine (p=0.02) groups differed significantly from those in the placebo group. However, the difference between theanine/arginine and theanine groups, was not statistically significant (p=0.74). From this study, no clear conclusion could be drawn regarding the potentiating effect of theanine and arginine combined ingestion on anti-stress effects in human.

著者

Keiko Unno Hiroshi Yamada Kazuaki Iguchi Hitoshi Ishida Yasunori Iwao Akio Morita Yoriyuki Nakamura

出版者

公益社団法人日本薬学会

雑誌

Biological and Pharmaceutical Bulletin (ISSN:09186158)

巻号頁・発行日

vol.40, no.6, pp.902-909, 2017-06-01 (Released:2017-06-01)

参考文献数

38

被引用文献数

19

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Theanine, an amino acid in tea, has significant anti-stress effects on animals and humans. However, the effect of theanine was blocked by caffeine and gallate-type catechins, which are the main components in tea. We examined the anti-stress effect of green tea with lowered caffeine, low-caffeine green tea, on humans. The study design was a single-blind group comparison and participants (n=20) were randomly assigned to low-caffeine or placebo tea groups. These teas (≥500 mL/d), which were eluted with room temperature water, were taken from 1 week prior to pharmacy practice and continued for 10 d in the practice period. The participants ingested theanine (ca. 15 mg/d) in low-caffeine green tea. To assess the anxiety of participants, the state-trait anxiety inventory test was used before pharmacy practice. The subjective stress of students was significantly lower in the low-caffeine-group than in the placebo-group during pharmacy practice. The level of salivary α-amylase activity, a stress marker, increased significantly after daily pharmacy practice in the placebo-group but not in the low-caffeine-group. These results suggested that the ingestion of low-caffeine green tea suppressed the excessive stress response of students. This study was registered at the University Hospital Medical Information Network (ID No. UMIN14942).

著者

Keiko Unno Shigenori Noda Yohei Kawasaki Hiroshi Yamada Akio Morita Kazuaki Iguchi Yoriyuki Nakamura

出版者

SOCIETY FOR FREE RADICAL RESEARCH JAPAN

雑誌

Journal of Clinical Biochemistry and Nutrition (ISSN:09120009)

巻号頁・発行日

vol.61, no.3, pp.210-216, 2017 (Released:2017-11-01)

参考文献数

51

被引用文献数

26

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Epidemiological and animal studies have demonstrated that ingestion of green tea enhances healthy life. However, caffeine in green tea can interfere with sleep. In this report, we examined the effect of green tea with lowered caffeine, low-caffeine green tea, on stress and sleep of the elderly. The participants (n = 10, mean age 89.3 ± 4.2 years) drank five cups/day of standard green tea for 1 week. Subsequently, they drank five cups/day of low-caffeine green tea for 2 weeks. Salivary α-amylase activity (sAA) was measured as a stress marker. Sleep stages were measured using a portable electroencephalography (n = 7, 6 female and 1 male). The level of sAA in the morning (sAAm) was significantly lower when the participants drank low-caffeine green tea than standard green tea. While the levels of sAAm were different among individuals, lower sAAm correlated with a higher quality of sleep. In those participants whose sAAm was lowered by the ingestion of low-caffeine green tea, some sleep parameters improved. Daily ingestion of low-caffeine green tea may be a beneficial tool for improving the quality of sleep of the elderly via the suppression of stress, although further research is required to fortify this hypothesis.