Kugako Sugimoto, NOST Tokyo
Origineel gepubliceerd op de site van Agentschap NL
Samenvatting
Een onderzoekgroup van Kanazawa University, heeft op basis van hun cohortstudie geopperd dat het drinken van groene thee cognitieve achteruitgang voorkomt. Het begin van (milde) cognitieve gebreken bij mensen die groene thee drinken komt minder voor dan bij mensen die geen groene thee drinken. Koffie en zwarte thee vertoonden geen effect. De resultaten van deze meer dan vijf jaar durende studie is gepubliceerd in Plos One (online, op 14, mei 2014)
Drinking green tea prevents cognitive decline
Summary
A research team of Kanazawa University has suggested that drinking green tea prevented cognitive decline in their cohort study. Onset of cognitive impairment and mild cognitive impairment for people who drank green tea occurred less compared to those who did not drink green tea. Coffee and black tea did not show such effect. This over-5-year study was published in Plos One (online, on May 14, 2014).
Details
Professor Masahito Yamada and Dr. Moeko Shinohara of Department of Neurology and Neurobiology of Aging of the Kanazawa University Graduate School of Medical Science have suggested that drinking green tea prevents cognitive decline based on their 5-year cohort study in Ishikawa prefecture. This research was conducted by interviewing 723 people aged over 60 years old from 2007 to 2008. The frequency of drinking green tea, coffee, and black tea was part of the interview. Cognitive function and blood were also tested in the first interview. From 2011 to 2013, the research team conducted follow-up interviews with 490 persons whose cognitive functions were normal at the first interview in 2007-2008. The average observation period was 4.9 years. Data of interviews was analyzed by multivariate logistic regression*. In this study, cognitive decline included (mild) cognitive impairment.
Results
18.4% (90 people) of the people who were interviewed for the second interview had (mild) cognitive impairment. One group that drank green tea at the frequency of 1 – 6 days a week showed significantly (p<0.05) lower value of the onset of cognitive decline compared to the control group. The control group consisted of people who did not drink any green tea, black tea, and coffee. A group that drank more than one cup of green tea a day also showed significantly lowered value (one thirds) of the onset of cognitive impairment. On the other hand, groups of people who drank coffee and black tea frequently did not show any significant difference. This study was online published in May 14, 2014 on Plos One.
Professor Yamada mentioned the study results had quite high credibility because the research followed healthy adults for almost 5 years. Unfortunately, it is not yet investigated what aspects or components of green tea had effects on slowing down the onset of cognitive decline. However, drinking green tea seems to be a suitable way for the Japanese to prevent cognitive decline because green tea is a popular drink in Japan.
Effect of Green tea
Green tea is made from the leaves from Camellia sinensis. Oxidation associated with preparation process is minimized for green tea, while such minimization does not apply to black tea and oolong tea. Green tea contains catechin, a polyphenol, which is known to have antioxidative, anti-inflammatory, antithrombotic, and plasma antioxidant effect. Before the present cohort study, green tea had been examined frequently in other cohort studies. In the study of the effect of green tea on cerebral vascular disorder (38029 males, 42949 females residing in Japan, 45 – 74 years old, observation 3 years), a group that drinks green tea everyday had a lower rate of incidence of cardiovascular disease, stroke, and cerebral thrombosis compared to the control groups that did not drink green tea at all or less frequently. In other cohort study on gastric cancers (almost 90,000 males and females residing in Japan, 40 – 69 years old), a female group who drank more than 5 cups of green tea a day had 30% lowered risk of gastric cancer compared to the control group that did not drink green tea. However, male groups did not show such a lowered risk rate. In addition, there are also reports that green tea did not show any effects on the prevention of gastric cancer in other study.
It seems that green tea has some positive influence on improving health. However, the effects of green tea need further investigation at this moment. In addition, the frequency and amount for effective drinking green tea should be established. However, if people like green tea, moderate drinking will not hurt them. It is a good way to enjoy drinking and to expect improvement of health at the same time.
Sources
News release of Kanazawa University, May 15, 2014 (in Japanese)
Kokubo et al. 2013 (Journal of the American Heart Association)
Sasazuki et al. 2004 (Cancer Causes Control 15(5):483-491)
*multivariate logistic regression
