Abstract
BackgroundGreen tea is a beverage with potential effects on cognitive dysfunction, as indicated by results of experimental studies. However, its effects in humans, especially at real-world (typical) consumption levels, are unclear.MethodsA double-blind, randomized controlled study was conducted to assess the effects of green tea consumption on cognitive dysfunction (Mini-Mental State Examination Japanese version (MMSE-J) score <28) in Japan. Participants were randomly allocated to the green tea or placebo group, and consumed either 2 g/day of green tea powder (containing 220.2 mg of catechins) or placebo powder (containing 0.0 mg of catechins), respectively, for 12 months. Cognitive function assessments were performed every 3 months using the MMSE-J and laboratory tests.ResultsThirty-three nursing home residents with cognitive dysfunction were enrolled (four men, 29 women; mean age ± SD, 84.8 ± 9.3; mean MMSE-J score ± SD, 15.8 ± 5.4), of whom 27 completed the study. Changes of MMSE-J score after 1 year of green tea consumption were not significantly different compared with that of the placebo group (−0.61 [−2.97, 1.74], least square mean (LSM) difference [95 % CI]; P = 0.59). However, levels of malondialdehyde-modified low-density lipoprotein (U/L), a marker of oxidative stress, was significantly lower in the green tea group (−22.93 [−44.13, −1.73], LSM difference [95 % CI]; P = 0.04).ConclusionsOur results suggest that 12 months green tea consumption may not significantly affect cognitive function assessed by MMSE-J, but prevent an increase of oxidative stress in the elderly population. Additional long-term controlled studies are needed to clarify the effects.Trial registration UMIN000011668 Electronic supplementary materialThe online version of this article (doi:10.1186/s12937-016-0168-7) contains supplementary material, which is available to authorized users.
Highlights
Green tea is a beverage with potential effects on cognitive dysfunction, as indicated by results of experimental studies
Green tea is a beverage with anti-oxidative stress and neuromodulating properties, as revealed by experimental studies in vitro and in vivo [12,13,14]; this is supported by clinical studies [15, 16]
Only 3 intervention studies on the effect of green tea consumption on cognitive dysfunction were conducted [26,27,28]. All of these intervention studies suggested that green tea or green tea-based dietary supplements may reduce the rate of cognitive decline or even improve cognitive function
Summary
Green tea is a beverage with potential effects on cognitive dysfunction, as indicated by results of experimental studies. Ide et al Nutrition Journal (2016) 15:49 number of epidemiological studies suggest that lifestyle, including dietary and nutritional factors, is related to risk of dementia [6,7,8,9]. In addition to these studies and the pathophysiology of dementia suggests that the modification of oxidative stress is important for preventing the disease and limiting its progression [8, 10, 11]. One of them used green tea-based supplements [28], and the results of other two studies were inconclusive [26, 27]
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