Drinking dark tea every day could help to reduce the risk of developing type 2 diabetes, a conference has heard.
Research presented at the European Association for the Study of Diabetes (EASD) meeting in Hamburg, Germany, showed people who drank dark tea every day had 53% lower risk for prediabetes and 47% reduced risk for type 2 diabetes compared to those who never drink tea.
Co-lead author Associate Professor Tongzhi Wu from the University of Adelaide, Australia, said: “The substantial health benefits of tea, including a reduced risk of cardiovascular disease and type 2 diabetes, have been reported in several studies over recent years, but the mechanisms underlying these benefits have been unclear.
“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.”
The team of the observational study, which also include researchers from Southeast University, China, believe the unique way in which dark tea is produced may provide the beneficial effects on metabolic control.
These include microbial fermentation, which help to improve both insulin sensitivity and the performance of beta cells in the pancreas and change the composition of the bacteria in the gut.
This research included 1,923 adults – 562 men,1,361 women aged 20-80 years – living in eight provinces in China. Of those, 436 had diabetes, 352 prediabetes and 1,135 had normal blood glucose levels.
Participants included 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 they consumed and the team examined the association between the frequency and type of tea consumption and excretion of glucose in the urine, insulin resistance, and glycaemic status.
After accounting for differences in age, sex, and clinical and lifestyle factors, the analysis found drinking tea daily was associated with an increase in urinary glucose excretion – UGCR by 0.11 mmol/mmol – and a reduction in insulin resistance – TyG by -0.23, as well as 15% lower risk for prediabetes and 28% reduced risk for type 2 diabetes, compared to those who never drank tea.
The health benefits were stronger among those who drank dark tea, with consumption associated with an increase in UGCR by 0.16 mmol/mmol and a reduction in TyG by 0.31.
Associate Prof Wu said: “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 (SGLT2) 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 effect on the heart and kidneys.”
Co-lead author Professor Zilin Sun from Southeast University added: “Our findings suggest that drinking dark tea every day has the potential to lessen type 2 diabetes risk and progression through better blood sugar control. When you look at all the different biomarkers associated with habitual drinking of dark tea, it may be one simple step people can easily take to improve their diet and health.”
The authors say although their findings are from an observational study, they believe they are promising.
They are undertaking a double-blind, randomised trial to investigate the benefits of dark tea on blood glucose control in people living with type 2 diabetes to validate their findings.
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