Drinking at least four cups a day was associated with a 17% lower risk of developing type 2 diabetes over an average 10-year period, according to research published on Saturday. The research, which has not yet been published in a scientific journal, will be presented this week at the European Association for the Study of Diabetes in Stockholm.
The relationship between tea drinking and the risk of type 2 diabetes has been previously studied, but the results have been inconclusive, said Xiaying Li, the study’s first author and a graduate student at Wuhan University of Science and Technology.
“Our study showed that the relationship between tea consumption and (type 2 diabetes) depended on the amount of tea consumed. Sufficient tea consumption may show clinical effects,” Li said via email. “Based on our findings, I would recommend citizens to consume more tea in their daily lives, if appropriate.”
At first, researchers found that tea drinkers and non-drinkers had a similar risk of type 2 diabetes.
But when researchers decided to examine whether the amount consumed made a difference among tea drinkers, in a systematic review of 19 cohort studies with more than a million adults in eight countries, the results were mixed: the more cups of green, oolong or more. The more black tea participants drank every day, the lower their risk of developing type 2 diabetes. The measures followed in these studies were as follows: participants drank less than one cup of tea a day, three cups a day, or four or more.)
The authors note that their research does not prove that drinking tea reduces the risk of type 2 diabetes, but suggests that drinking tea probably helps, according to a news release. They also noted that they relied on participants’ self-reported assessments of their tea consumption and could not rule out the possibility that unmeasured lifestyle and physiological factors may have influenced the results.
Experts who did not participate in the study agreed with the authors’ recognition of the shortcomings of the current study.
“It’s possible that people who drink more tea avoid or drink less sugary drinks or equivalents, or engage in other health behaviors that lead to a lower risk of type 2 diabetes,” said Naveed Sattar, professor of metabolic medicine. The University of Glasgow said in a statement.
“The findings should be taken with a very large grain of salt (or cup of tea),” Kevin McConway, emeritus professor of applied statistics at the UK’s Open University, said in a statement. “The problem with meta-analysis findings is that the devil is always in the detail, and we don’t have the details. Which studies were included? What was their quality? Which people, from which countries, were they studied?”
“Certain components of tea, such as polyphenols, can reduce blood glucose concentration by inhibiting the activity of α-glucosidase and/or inhibiting the activity of other enzymes, but a sufficient amount of the bioactive substance is required to be effective,” Li said. .
The take-home message is that lifestyle choices are important in managing the risk of type 2 diabetes, Duane Mellor, a dietitian and senior lecturer at Aston University in Birmingham, UK, said in a statement. Mellor was not involved in the investigation.