Drinking more tea may reduce the risk of developing type 2 diabetes, according to a study of more than a million adults.
Four or more cups of black, green, or oolong tea daily are associated with a 17 percent lower risk of developing type 2 diabetes.
Moderate consumption of black, green or oolong tea is associated with a lower risk of developing type 2 diabetes (T2D), according to a systematic review and meta-analysis of 19 cohort studies involving more than 1 million adults from eight countries. .
The findings showed that drinking at least four cups of tea per day was associated with a 17% lower risk of T2D over an average of 10 years. The research will be presented at this year’s European Association for the Study of Diabetes (EASD) annual meeting in Stockholm, Sweden (September 19-23).
“Our results are interesting because they suggest that people can do something as simple as drinking four cups of tea a day to reduce their risk of type 2 diabetes,” said lead author Xiaying Li from Hannan University of Science and Technology in China.
Tea contains various antibacterial, anti-inflammatory and anti-carcinogenic compounds. While regular tea consumption has long been known to be beneficial to health due to these properties, the relationship between tea consumption and T2D is less clear. Published cohort studies and meta-analyses have so far reported inconsistent findings.
To address this uncertainty, investigators conducted a cohort study and dose-response meta-analysis to better determine the association between tea consumption and future T2D risk.
First, they studied 5,199 adults (2583 men, 2616 women) with a mean age of 42 years and no history of T2D who were recruited in 1997 and followed until 2009. A prospective study of the economics, sociological aspects, and health of residents from nine provinces.
At baseline, participants completed a food and beverage frequency questionnaire. They provided information on lifestyle factors such as regular exercise, smoking and alcohol consumption. A total of 2,379 (46%) participants reported drinking tea. At the end of the study, 522 (10%) participants developed T2D.
After researchers adjusted for factors known to be associated with T2D risk, such as age, gender, and lack of physical activity, tea drinkers had a similar risk of developing T2D compared to nondrinkers. Furthermore, the results did not change significantly when analyzed by age and sex, or when participants who developed diabetes during the first 3 years of follow-up were excluded.
In the next phase of the study, scientists conducted a systematic review of all cohort studies examining tea consumption and T2D risk in adults (aged 18 and older) through September 2021. In total, 19 studies involving 1,076,311 participants from eight countries (China, USA, Finland, Japan, United Kingdom, Singapore, Netherlands and France) were included in the dose-response meta-analysis.
They examined the effect of different types of tea (green tea, oolong tea, and black tea), tea drinking frequency (less than 1 cup/day, 1–3 cups/day, and 4 or more) on T2D risk. cups/day), gender (male vs. female), and study location (Europe vs. America or Asia).
Overall, the meta-analysis found a direct link between tea consumption and T2D risk, with each cup of tea consumed per day reducing the risk of T2D by 1%.
Compared to adults who didn’t drink tea, those who drank 1-3 cups a day had a 4% lower risk of developing T2D. What’s even more surprising is that people who ate at least 4 cups a day had a 17 percent lower risk.
Unions were protected regardless of the type of tea they drank, male or female, or where they lived. This suggests that the amount of tea consumed may play a greater role than any other factor.
“While more research is needed to determine the exact amount and mechanism behind these observations, our findings suggest that tea consumption may be beneficial in reducing the risk of type 2 diabetes, but only in large amounts (at least 4 cups per day),” says Lee.
She added, “Certain compounds in tea, such as polyphenols, may lower blood glucose levels, but sufficient amounts of these bioactive compounds may be required to be effective.” This explains why we did not find an association between tea consumption and type 2 diabetes in our cohort study because we did not observe high tea consumption.
Oolong tea is a traditional Chinese tea made from the same plant used to make green and black tea. The difference is how the tea is made: green tea is not allowed to oxidize much, black tea is allowed to oxidize until it turns black, and oolong tea is partially oxidized.
Although there are important findings, the authors of the study is observational. Therefore, it cannot prove that tea consumption is the cause of the reduced risk of T2D, although it does suggest that it is a contributory factor.
In addition, the research team suggested several recommendations, considering the amount of tea consumed, they cannot exclude the possibility that confounding by other lifestyle and physiological conditions may affect the results.
The study was funded by the Young Talent Project of the Health Commission of Hubei Province, China. Science and Technology Research Key Project by Education Department of Hubei Province, China; Sanuo Diabetes Charity, China; and Xiangyang Science and Technology Planning Project, China.