One of the most widely consumed beverages in the world – next to coffee, itself the subject of much health research – tea is often singled out for its soothing, anti-stress and beneficial properties.
Some of these have already been the subject of much research, in particular on well-being and cognitive function, but its impact on diabetes is now attracting scientific interest.
A new study by researchers from the University of Adelaide, Australia, and Southeast University, China, reveals that daily consumption of dark tea – also known as fermented tea or post-fermented tea – may help control blood-sugar levels and reduce the risk of diabetes.
Presented at the annual meeting of the European Association for the Study of Diabetes in Hamburg, Germany, the study involved 1,923 adults aged between 20 and 80 from eight Chinese provinces. Of the participants, 436 had diabetes, 352 had pre-diabetes, and 1,135 had normal blood-sugar levels.
The researchers asked them about the frequency of their tea consumption, as well as the type of tea consumed, and then studied a potential association with various parameters such as glucose excretion in urine, insulin resistance, and glycaemic status.
Better blood-sugar control
“Our findings hint at the protective effects of habitual tea drinking on blood-sugar management via increased glucose excretion in urine, improved insulin resistance and, thus, better control of blood sugar. These benefits were most pronounced among daily dark tea drinkers,” explained Tongzhi Wu of the University of Adelaide.
The researchers point out that this phenomenon could be linked to the way dark teas, such as pu’er cha, is produced, “which involves microbial fermentation” on top of their high content of antioxidants and anti-inflammatory properties.
Specifically, the study reports that daily tea consumption is associated with a 15% reduction in the risk of pre-diabetes and a 28% reduction in the risk of type-2 diabetes, irrespective of the type of tea consumed.
And the relationship is even more significant with dark tea, with a 53% reduction in the risk of pre-diabetes and 47% in the risk of type-2 diabetes.
“When you look at all the various biomarkers associated with habitual drinking of dark tea, it may be one simple step people can easily take to improve their diet and health,” said co-lead author Zilin Sun.
Boost to longevity
This isn’t the only study to extol the health benefits of tea: just over a year ago, researchers at the US National Institutes of Health looked at the effects of black tea consumption on mortality in the United Kingdom.
They found that participants drinking two or more cups of black tea a day were 9-13% less likely to die than those who drank no tea at all.
“The associations were observed regardless of whether participants also drank coffee, added milk or sugar to their tea, their preferred tea temperature, or genetic variants related to caffeine metabolism. The findings suggest that tea, even at higher levels of intake, can be part of a healthy diet,” this study concluded.