• New research found that drinking a cup of dark tea every day may reduce someone's risk of type 2 diabetes.
  • Study authors note that while more research is needed to validate the clinical benefits of dark tea, adding regular consumption of dark tea into your routine is a low-risk, beneficial lifestyle habit.
  • Experts recommend patients look for a natural dark tea without any artificial sweeteners.

A daily cup of dark tea may help reduce the risk of type 2 diabetes in adults, a new study finds.


According to research presented at this year’s Annual Meeting of The European Association for the Study of Diabetes, people who consume dark tea every day have a 53% lower risk for prediabetes and 47% lower risk for type 2 diabetes.


Prediabetes is having high blood sugar levels; type 2 diabetes is characterized by insulin resistance when the body has a problem processing sugar as fuel.


“This study showed in a general Chinese population that habitual tea consumption, particularly dark tea, was associated with reduced risk of both prediabetes and diabetes,” Tongzhi Wu, MD, PhD, the study’s co-lead author, associate professor from the University of Adelaide, and mid-career fellow for the Hospital Research Foundation Group told Health.


Wu explained that previous studies showcase numerous benefits of tea consumption, like reduced inflammation and improved insulin sensitivity.


The new research focused on another aspect of diabetes risk.


“Our study showed that it is associated with increased urinary glucose excretion, which may also contribute to its glycemic benefits,” Wu said.


Since the study used data collected via standardized questionnaires from a community-dwelling population, Wu noted that further interventional trials are needed to validate the clinical benefits of dark tea.


But, the new study’s conclusions can still be easily adapted as a low-risk lifestyle habit.


Woman pouring a hot kettle to make a cup of tea

Getty Images / ferrantraite
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How Dark Tea Impacts Blood Sugar and Diabetes Risk

The underlying mechanism for dark tea’s impact on diabetes risk may be related to increased excretion of glucose in the urine as well as improved insulin sensitivity, Caroline Messer, MD, an endocrinologist at Northwell Lenox Hill Hospital, told Health.

“Dark tea might work with the kidneys to get glucose out of the blood and into the urine, and by improving insulin sensitivity in muscle and fat,” Gutierrez said.

Research shows dark tea, specifically black tea, is filled with antioxidants which can help reduce oxidative stress and lower the risk of developing a chronic illness.

A 2018 study demonstrated the impact of drinking black tea on blood sugar levels by having participants drink a high-sugar beverage paired with either a low- or high-dose of black tea or a placebo. The people who drank the low or high-dose of black tea had lower blood sugar compared to those who drank a placebo.


“The theaflavins and thearubigins may reduce cholesterol and blood sugar levels,” Divya Yogi-Morren, MD, medical director of the Cleveland Clinic Pituitary Center, department of endocrinology, diabetes and metabolism, told Health.


What Is Dark Tea?

Absalon Gutierrez, MD, an endocrinologist with UTHealth Houston explained that dark tea is a highly oxidized tea. In addition to its oxidation length, dark tea is unique in its production and is the only kind that involves microbial fermentation.


Dark tea has a variety of benefits that contribute to overall well-being, which may in turn contribute to a lowered diabetes risk.


“The catechins from oolong tea have also been shown in some studies to reduce body weight and decrease body fat,” Yogi-Morren said. “It also affects the type of bacteria in the gut that may play a role in reducing the risk of diabetes by promoting the growth of good bacteria and inhibiting the growth of bad bacteria.”


Dark tea may modulate glucose excretion in the kidney which means that more glucose may be excreted from the body lowering the risk of high blood sugars and diabetes, she explained.


Additionally, the unique fermentation process results in the creation of bioactive compounds that have antioxidants and anti-inflammatory effects that increase insulin sensitivity and the performance of beta cells in the pancreas.


Diabetes is caused by either decreased insulin production from the pancreas or reduced insulin sensitivity, Yogi-Morren explained. When insulin production and sensitivity are improved, there is a lower chance of developing diabetes.


Lastly, dark tea may enhance insulin action, improve insulin resistance, protect the beta cells in the pancreas that produce insulin, remove free radicals from the body, and decrease inflammation, Yogi-Morren said.


If you’re choosing a dark tea to add to your pantry, Gutierrez recommends a natural dark tea without added artificial ingredients.


While more research is still needed to confirm dark tea’s impact on diabetes risk, adding dark tea to your routine is still a worthwhile endeavor.


“Our observations support the concept of regularly drinking tea," Wu said, "particularly dark tea, as a safe and inexpensive dietary approach, to reduce the risk of prediabetes and diabetes."


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