Elderly adults who regularly drink green tea may stay more agile and independent than their peers over time, according to a Japanese study that covered thousands of people.
For the new study, published in the American Journal of Clinical Nutrition, researchers decided to examine the question of whether green tea drinkers have a lower risk of frailty and disability as they grow older.
Yasutake Tomata of the Tohoku University Graduate School of Medicine and his colleagues followed nearly 14,000 adults aged 65 or older for three years.
They found those who drank the most green tea were the least likely to develop "functional disability," or problems with daily activities or basic needs, such as dressing or bathing.
Specifically, almost 13 percent of adults who drank less than a cup of green tea per day became functionally disabled, compared with just over 7 percent of people who drank at least five cups a day.
"Green tea consumption is significantly associated with a lower risk of incident functional disability, even after adjustment for possible confounding factors," Tomata and his colleagues wrote.
The study did not prove that green tea alone kept people spry as they grew older.
Green-tea lovers generally had healthier diets, including more fish, vegetables and fruit, as well as more education, lower smoking rates, fewer heart attacks and strokes, and greater mental sharpness.
They also tended to be more socially active and have more friends and family to rely on.
But even with those factors accounted for, green tea itself was tied to a lower disability risk, the researchers said.
People who drank at least five cups a day were one-third less likely to develop disabilities than those who had less than a cup per day. Those people who averaged three or four cups a day had a 25 percent lower risk.
Although it's not clear how green tea might offer a buffer against disability, Tomata's team did note that one recent study found green tea extracts seem to boost leg muscle strength in older women.
While green tea and its extracts are considered safe in small amounts, they do contain caffeine and small amounts of vitamin K, which means it could interfere with drugs that prevent blood clotting.
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SOURCE
Study-
Green tea consumption and the risk of incident functional disability in elderly Japanese: the Ohsaki Cohort 2006 Study1,2,3
Yasutake Tomata, Masako Kakizaki, Naoki Nakaya, Toru Tsuboya, Toshimasa Sone, Shinichi Kuriyama, Atsushi Hozawa, and Ichiro Tsuji
© 2012 American Society for Nutrition
Abstract
Background: Previous studies have reported that green tea consumption is associated with a lower risk of diseases that cause functional disability, such as stroke, cognitive impairment, and osteoporosis. Although it is expected that green tea consumption would lower the risk of incident functional disability, this has never been investigated directly.
Objective: The objective was to determine the association between green tea consumption and incident functional disability in elderly individuals.
Design: We conducted a prospective cohort study in 13,988 Japanese individuals aged ≥65 y. Information on daily green tea consumption and other lifestyle factors was collected via questionnaire in 2006. Data on functional disability were retrieved from the public Long-term Care Insurance database, in which subjects were followed up for 3 y. We used Cox proportional hazards regression analysis to investigate the association between green tea consumption and functional disability.
Results: The 3-y incidence of functional disability was 9.4% (1316 cases). The multiple-adjusted HR (95% CI) of incident functional disability was 0.90 (0.77, 1.06) among respondents who consumed 1–2 cups green tea/d, 0.75 (0.64, 0.88) for those who consumed 3–4 cups/d, and 0.67 (0.57, 0.79) for those who consumed ≥5 cups/d in comparison with those who consumed <1 cup/d (P-trend < 0.001).
Conclusion: Green tea consumption is significantly associated with a lower risk of incident functional disability, even after adjustment for possible confounding factors.
INTRODUCTION ONLY
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Tea is the most frequently consumed beverage in theworld. Three billion kilograms of tea are produced worldwide annually. Because of the high rates of tea consumption in the global population, even small effects on an individual could have a large impact on public health.
The health effects of green tea have been extensively investigated by prospective cohort studies. We have found that green tea consumption is significantly associated with a lower risk of mortality due to stroke (1) and pneumonia (2) and a lower risk of cognitive impairment (3), depression (4), and psychological distress (5).
These results have been confirmed by other researchers (6–9). In addition, other epidemiologic studies have indicated that green tea consumption is associated with a lower risk of osteoporosis (10, 11), and randomized controlled trials have indicated that green tea is effective for cardiovascular risk factors (12, 13).
Because all of the above conditions are major causes of functional disability (14–16), it is expected that green tea consumption would contribute to disability prevention. To our knowledge, however, no study has yet investigated the relation between green tea consumption and the incident risk of functional disability.
We therefore conducted the present analysis to test the hypothesis that green tea consumption is associated with a lower risk of developing functional disability.
SUBJECTS AND METHODS
Study cohort
The design of the Ohsaki Cohort 2006 Study has been described in detail elsewhere (17). In brief, the source population for the baseline survey comprised 31,694men and women aged 65 y who were living in Ohsaki City, northeastern Japan, on 1 December 2006.
The baseline survey was conducted between 1 December and 15 December 2006. A questionnaire was distributed by the heads of individual administrative districts to individual households and then collected by mail.
In this analysis, 23,091 persons who provided valid responses formed the study cohort (Figure 1). We excluded 6333 persons who did not provide written consent for review of their Long-term Care Insurance (LTCI) information, 1979 persons who had already been certified as having disability by the LTCI at the time of the baseline survey, 5 persons who had died or moved out of the district during the period of the baseline 1 From the Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (YT, MK, NN, TT, TS, SK, AH, and IT); the Department of Nutrition and Dietetics, Faculty of Family and Consumer Sciences, Kamakura Women’s University, Kamakura, Japan (NN); and the Department of Public Health, Yamagata University Graduate School of Medical Science, Yamagata, Japan (AH).
2 Supported by Health Sciences Research grants (nos. H21-Choju-Ippan-001 and H22-Choju-Ippan-001) from the Ministry of Health, Labor, and Welfare of Japan.
3 Address reprint requests and correspondence to Y Tomata, Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan. E-mail: y-tomata@med.tohoku.ac.jp.
Received July 12, 2011. Accepted for publication December 22, 2011. doi: 10.3945/ajcn.111.023200.
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