Study finds dark tea beneficial for controlling blood sugar

Sydney: Drinking dark tea every day may help in controlling blood sugar to reduce diabetes risk, finds a new study.

Dark tea, which originated in China, is a microbially fermented type of tea. The fermentation continues several months to many years and the leaves are often pressed in a cake or brick shape.

The research presented at the ongoing European Association for the Study of Diabetes (EASD) in Hamburg, Germany, showed that daily consumers of dark tea had 53 per cent lower risk for prediabetes and 47 per cent reduced risk for type 2 diabetes.

“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,” said Tongzhi Wu, study’s co-lead author and Associate Professor at University of Adelaide in Australia.

Along with researchers from the Southeast University in China, the team conducted the study on 1,923 adults of 20 to 80 years. Of this, 436 participants were living with diabetes and 352 with prediabetes, 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 (i.e. green, black, dark, or other tea) of tea consumption.

The team examined the association between both the frequency and type of tea consumption and excretion of glucose in the urine, insulin resistance (measured using the triglyceride and glucose index), and glycaemic status (defined as a history of type 2 diabetes).

Researchers also found that drinking tea every day was associated with an increase in urinary glucose excretion and a reduction in insulin resistance, as well as 15 per cent lower risk for prediabetes and 28 per cent reduced risk for type 2 diabetes, compared with never tea-drinkers.

“These findings suggest that the actions of bioactive compounds in dark tea may directly or indirectly modulate glucose excretion in the kidneys, an effect, to some extent, mimicking that of sodium-glucose co-transporter-2 inhibitors, a new anti-diabetic drug class that is not only effective at preventing and treating type 2 diabetes, but also has a substantial protective effects on the heart and kidneys,” Wu added.

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.