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.

Green tea is known to have various health benefits for humans. However, the effect of green tea consumption on cognitive dysfunction remains to be clinically verified. We conducted a clinical study to investigate the effects of green tea consumption on cognitive dysfunction. Twelve elderly nursing home residents with cognitive dysfunction (Mini-Mental State Examination Japanese version (MMSE-J) score: <28) participated in the study (2 men, 10 women; mean age, 88 years). The participants consumed green tea powder 2 g/day for 3 months. After three months of green tea consumption, the participants’ MMSE-J scores were significantly improved (before, 15.3 ± 7.7; after, 17.0 ± 8.2; p = 0.03). This result suggests that green tea consumption may be effective in improving cognitive function or reducing the progression of cognitive dysfunction; however, long-term large-scale controlled studies are needed to further clarify the effect.

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Despite considerable progress in the management of diabetes mellitus by synthetic drugs, the search for indigenous natural antidiabetic agents is ongoing. The plant kingdom offers a wide field to look for effective oral hypoglycemics. More than 400 species have been reported to display hypoglycemic effects, but only a few of them have been investigated.

Objective To determine whether ingesting a green tea beverage enriched with catechins with a galloyl moiety during a meal reduces body fat in moderately obese adults. Design Randomized double-blind placebo-controlled study. Subjects A total of 126 obese subjects (25 ≤ body mass index < 30 kg m(-2)) were randomly assigned to a group receiving green tea beverages without catechins (placebo), or a group receiving green tea beverages with a low or high content of catechins with a galloyl moiety. Each subject ingested 500 mL bottled green tea beverages containing 25, 180, or 279.5 mg green tea catechins (0, 149.5, or 246.5 mg catechins with a galloyl moiety, respectively), at mealtimes for 12 weeks; the subjects were instructed to ingest the beverage during the meal that had the highest fat content on that day. Methods Anthropometric measurements and blood chemistry analysis were performed during the run-in period; at weeks 0, 4, 8, and 12 of the intake period; and at the end of the withdrawal period. Abdominal fat area was measured by computed tomography at weeks 0, 8, and 12 of the intake period and at the end of the withdrawal period. Results Both the low- and high-dose groups exhibited significant reductions in visceral and subcutaneous fat areas compared to the control group at 12 weeks post-intervention. Conclusion Ingestion of a green tea beverage enriched with catechins with a galloyl moiety during a high-fat meal reduces body fat in moderately obese adults.