Tea drinkers, rejoice! New research reveals that drinking dark tea every day may help control blood sugar levels and reduce diabetes risk.
The observational study by researchers from the University of Adelaide in Australia and Southeast University in China found that compared with people who never drink tea, those who consume dark tea daily had 53% lower risk for prediabetes and 47% reduced risk for type 2 diabetes.
This is even after taking into account established risk factors known to drive the risk for diabetes, including age, gender, ethnicity, body mass index (BMI), average arterial blood pressure, fasting plasma glucose, cholesterol, alcohol intake, smoking status, family history of diabetes and regular exercise.
“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”, says the study’s co-lead author Associate Professor Tongzhi Wu from the University of Adelaide and The Hospital Research Foundation Group Mid-Career Fellow.
“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.”
These beneficial effects on metabolic control may lie in the unique way dark tea is produced, which involves microbial fermentation, a process that may yield unique bioactive compounds (including alkaloids, free amino acids, polyphenols, polysaccharides, and their derivatives) to exhibit potent antioxidant and anti-inflammatory effects, improve both insulin sensitivity and the performance of beta cells in the pancreas, and change the composition of the bacteria in the gut.
“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,” says Associate Professor Wu.
Co-lead author Professor Zilin Sun from Southeast University adds, “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.”
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.
They are currently conducting 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.
In addition, they cannot rule out the possibility that residual confounding by other lifestyle and physiological factors may have affected the results.