A 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.
The inclusion criteria were as follows: 1) ≥ 50 years of age; 2) ability to orally ingest green tea and placebo powder; 3) No consumption of food supplements with anti-oxidative stress effects (vitamins E, C, A, and β -carotene) during the study period; and 4) An MMSE-J score of <28 . The exclusion criteria were as follows: 1) tea allergy; 2) severe cardiac, respiratory, hepatic, or renal dysfunction; and 3) severe anemia.
The participants orally consumed 2.0 g/day of green tea or placebo powder. The green tea powder contained 220.2 mg of catechins (gallocatechin, 10.9 mg; epigallocatechin, 72.0 mg; catechin, 2.0 mg; epicatechin, 22.0 mg; epigallocatechin gallate, 88.0 mg; gallocatechin gallate, 8.0 mg; epicatechin gallate, 17.3 mg), 20.8 mg of theanine, and 60.0 mg of caffeine. The placebo powder consisted of 1.6 g of cellulose powder and 0.4 g of gardenia/caramel pigment and contained 0.0 mg of catechins.
Thirty-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.
The mean age of participants was 84.8 ± 9.3 years (placebo group, 87.9 ± 5.6 years; green tea group, 81.8 ± 11.1 years).
Seventeen participants had Alzheimer’ s disease (8 in the placebo group, 9 in the green tea group), 15 had vascular dementia (8 in the placebo group, 7 in the green tea group), and 1 in the green tea group had dementia with Lewy bodies. Among 33 participants, 5 were being treated with medications for dementia (3 in the placebo group, and 2 in the green tea group), and the doses of medications were not changed during the intervention period. All 33 participants habitually drank tea (≥ 1 cup/day), and none of the participants had a habit of consuming any type of dietary supplements.
Twelvemonth green tea consumption significantly maintained lower levels of oxidative stress marker MDA-LDL, but the MMSE-J score was not improved significantly.
MMSE-J scores were stable in each group during the study period, and this is a main limitation of this study. Green tea is not a medication, and our study used a dose that can be taken in daily-life situations. A 2 g/day intake of green tea powder (containing 220.2 mg of catechins) is equivalent to 2 to 4 cups/day of bottled or home-brewed green tea consumption.
In addition, all of the participants of this study were regular tea drinker, and tea consumption during the study period was not restricted because of ethical reasons. Therefore, baseline tea consumption might affect the changes and the differences of MMSE-J scores in both groups.
In addition to the non-restricted baseline tea consumption during the study period, the sex of the study subjects and the different types of dementia present in these patients are factors that may have interfered with the results, despite the even distribution of sexes and dementia patients between the experimental groups.
Our results suggest that 12-month green tea consumption may not significantly affect cognitive function assessed by the MMSE-J.
Source: Ide K, Yamada H, Takuma N, Kawasaki Y, Harada S, Nakase J, et al. Effects of green tea consumption on cognitive dysfunction in an elderly population: A randomized placebo-controlled study. Nutr J. 2016;15(49).
Konsumsi teh hijau rutin setiap hari sebanyak 2-4 porsi selama setahun tidak memperbaiki disfungsi kognitif pada lansia.