Journal
NUTRIENTS
Volume 9, Issue 7, Pages -Publisher
MDPI
DOI: 10.3390/nu9070777
Keywords
anti-stress effect; caffeine; green tea; middle-aged individuals; salivary alpha-amylase; sleep
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Funding
- KAKENHI [15K00828]
- University of Shizuoka
- Grants-in-Aid for Scientific Research [15K00828] Funding Source: KAKEN
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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 alpha-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.
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