Drinking dark tea every day may help control blood sugar to reduce diabetes risk, a study suggests.
Researchers in Australia and China found that compared with people who never drink tea, daily consumers of dark tea – where the leaves are fermented after being heated and shaped – had a 53 per cent lower risk for prediabetes and 47 per cent reduced risk for type 2 diabetes.
The results were true even after taking into account established risk factors known to drive the risk for diabetes, including age, gender, ethnicity, body mass index (BMI), alcohol intake, smoking status and family history of diabetes among other areas.
The study included 1,923 adults living across eight provinces in China. Some 436 people were living with diabetes, 352 with prediabetes – a serious health condition where blood sugar levels are higher than normal, but not high enough yet to be diagnosed as type 2 diabetes, and 1,135 had normal blood glucose levels.
Participants included both non-habitual tea drinkers and those with a history of drinking only a single type of tea. They were asked about the frequency and type of tea consumption.
The analysis found that drinking tea every day was associated with a reduction in insulin resistance and the health effects were most robust for dark tea drinkers.
The beneficial effects on metabolic control may lie in the unique way dark tea is produced, which involves microbial fermentation, a process that may boost metabolism to produce anti-inflammatory effects, improve both insulin sensitivity and change the composition of the bacteria in the gut.
Co-lead author Associate Professor Tongzhi Wu, from the University of Adelaide, said: “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.”
Despite the promising findings, the authors caution that as with any observational study, the findings cannot prove that drinking tea every day improves blood sugar control by increasing urinary glucose excretion and reducing insulin resistance, but suggest that they are likely to contribute.
