Drinking four or more cups of tea a day could reduce the risk of type 2 diabetes, research suggests.
One study found that drinking black, green, or oolong tea every day was linked to a 17% lower risk of diabetes over an average of 10 years.
Drinking one to three cups a day reduces the risk by 4%.
The results, presented at the annual meeting of the European Association for the Study of Diabetes in Stockholm, are based on a review of 19 studies involving more than one million people.
They have not yet been peer-reviewed or published in a journal.
Lead author Xiaying Li, of Wuhan University of Science and Technology in China, said, “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 the risk of develop type 2 diabetes. “
Previous research has found that tea may be beneficial to health, in part because it contains antioxidants and polyphenols, which can protect against disease.
However, to reduce the risk of type 2 diabetes, experts agree that people should primarily keep their weight in check.
Obesity is a leading cause of type 2 diabetes, accounting for 80 to 85 percent of the risk of developing the condition.
Obese people are thought to be up to 80 times more likely to develop type 2 diabetes than those with a BMI below 22.
In the new study in China, the researchers first looked at data from 5,199 adults from the China Health and Nutrition Survey who did not have diabetes, who were recruited in 1997 and followed through 2009.
People completed a food and drink frequency questionnaire and provided information on lifestyle factors such as regular exercise, smoking, and alcohol consumption.
This study found no benefit from drinking tea on diabetes risk.
But when the researchers carried out a systematic review of studies existing through September 2021 from eight countries, the results differed.
This analysis suggested that every cup of tea a day reduced the risk of developing type 2 diabetes by about 1%.
The results were true regardless of what type of tea people drank, male or female, and regardless of where they lived.
Xiaying Li said tea has been shown to reduce risk, but only when drunk in large enough quantities.
He added: “It is possible that particular components of tea, such as polyphenols, can reduce blood glucose levels, but enough of these bioactive compounds may be needed to be effective.
“It might also explain why we didn’t find an association between tea consumption and type 2 diabetes in our cohort study, because we didn’t consider higher tea consumption.”
When it comes to whether the reduced risks were valid if people added milk to their tea, the authors said they reviewed previously published literature on this issue.
This showed that “dairy and dairy products were associated with a reduced risk of diabetes,” they wrote.
Naveed Sattar, professor of metabolic medicine at the University of Glasgow, said: ‘Given the nature of this study, it cannot prove that tea prevents diabetes by itself.
“Rather it could be that people who drink more tea avoid or less often drink sugary drinks or more harmful equivalents or have other health behaviors that lead them to have lower risks of type 2 diabetes.
“There is no evidence whatsoever that the chemicals in tea prevent diabetes, so I suspect it is more about tea being healthier (less caloric) than many alternative drinks or tea drinkers who lead longer lives. healthy in general “.
Matt Sydes, Professor of Clinical Studies and Methodology in the Medical Research Council’s Clinical Studies Unit, said, “This is large observational data. It is not a randomized controlled trial, so there is a lot of room for the data to be misunderstood.
“It is important to point out that everyone drinks liquids. If there is an effect here (and this is a big if), it may not depend on the tea they drink, but on what they don’t drink because they are drinking tea at those times.
“You can’t tell right now.”