Drinking plenty of tea may reduce the risk of developing type 2 diabetes, according to a study of more than one million adults.
Four or more cups of black, green or oolong tea each day are linked to a 17% reduction in the risk of developing type 2 diabetes.
Moderate consumption of black, green or Oolong tea is linked to a lower risk of developing type 2 diabetes (T2D), according to the results of a systematic review and a meta-analysis of 19 cohort studies involving more than one million adults from eight countries.
The results suggest that drinking at least four cups of tea a day is associated with a 17% lower risk of T2DM over an average period of 10 years. The study will be presented at this year’s European Association for the Study of Diabetes (EASD) annual meeting in Stockholm, Sweden (September 19-23).
“Our findings are exciting because they suggest that people can do something as simple as drinking four cups of tea a day to potentially reduce their risk of developing type 2 diabetes,” says lead author Xiaying Li of Wuhan University of Science and Technology in China.
Tea contains various antioxidant, anti-inflammatory and anti-carcinogenic compounds. Although it has long been known that regular tea consumption may benefit health due to these properties, the relationship between tea consumption and the risk of T2D is less clear. Cohort studies and meta-analyses published so far have reported inconsistent results.
To address this uncertainty, the researchers conducted a cohort study and dose-response meta-analysis to better define the relationship between tea consumption and future risk of T2DM.
They first studied 5,199 adults (2,583 men, 2,616 women) with an average age of 42 and no history of T2D from the China Health and Nutrition Survey (CHNS), recruited in 1997 and followed through 2009. The CHNS is a multicenter prospective study focusing on the economy, sociological issues, and the health of residents of nine provinces.
At baseline, participants completed a food and drink frequency questionnaire. They also provided information on lifestyle factors such as regular exercise, smoking and alcohol consumption. Overall, 2,379 (46%) participants reported drinking tea. At the end of the study, 522 (10%) participants had developed T2DM.
Researchers found that tea drinkers had a similar risk of developing T2DM compared to non-drinkers after adjusting for factors known to be linked to an increased risk of T2DM, such as age, gender and inactivity. physical. Additionally, the results did not change significantly when analyzed by age and sex, or when participants who developed diabetes within the first 3 years of follow-up were excluded.
In the next stage of the study, the scientists carried out a systematic review of all cohort studies looking at tea consumption and the risk of T2DM in adults (aged 18 or older) up to September 2021. A total of 19 cohort studies involving 1,076,311 participants from eight countries (China, USA, Finland, Japan, UK, Singapore, Netherlands and France) were included in the dose-response meta-analysis.
They explored the potential impact on T2D risk of different types of tea (green tea, oolong tea and black tea), frequency of tea consumption (less than 1 cup/day, 1-3 cups/day and 4 or more cups/day), gender (male and female) and study location (Europe and America, or Asia).
Overall, the meta-analysis found a linear association between tea consumption and the risk of T2D, with each cup of tea consumed per day reducing the risk of developing T2D by approximately 1%.
Compared to adults who did not drink tea, those who drank 1 to 3 cups a day reduced their risk of T2DM by 4%. Even more impressively, those who consumed at least 4 cups a day reduced their risk by 17%.
The associations were maintained regardless of what type of tea the participants drank, whether they were male or female, or where they lived. This suggests that it may be the amount of tea consumed, rather than any other factor, that plays a major role.
“Although further research is needed to determine the exact dosage and the mechanisms behind these observations, our results suggest that tea consumption is beneficial in reducing the risk of type 2 diabetes, but only at high doses ( at least 4 cups a day),” Li said.
She adds, “It is possible that particular components of tea, such as polyphenols, may reduce blood glucose levels, but sufficient amounts of these bioactive compounds may be required to be effective. This may also explain why we did not find an association between tea consumption and type 2 diabetes in our cohort study, as we did not examine higher tea consumption.
Oolong tea is a traditional Chinese tea made from the same plant used to make green and black teas. The difference is in how the tea is processed – green tea cannot oxidize much, black tea can oxidize until it turns black, and oolong tea is partially oxidized.
Despite the important findings, the authors note that the study is observational. Therefore, it cannot prove that tea consumption is the cause of the reduced risk of T2D, although it suggests that it is a likely contributor.
Additionally, the research team points out several caveats, including that they relied on subjective assessments of the amounts of tea consumed and cannot rule out the possibility that residual confusion due to other physiological and lifestyle factors may have affected the results.
The study was funded by the Young Talents Project of the Hubei Provincial Health Commission, China; Science and Technology Research Key Project of Education Department of Hubei Province, China; Sanuo Diabetes Charity Foundation, China; and Xiangyang Science and Technology Plan Project, China.
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