Researchers are testing whether Jinhua dark tea, a naturally fermented Chinese tea, could help people with type 2 diabetes manage their blood sugar levels better. This large study will follow 264 people over one year, comparing those who drink the tea alongside their regular diabetes medications with those who only take their medications. Scientists chose this tea because early lab and animal studies showed it might lower blood sugar and improve cholesterol levels, but they need to prove it works in real people. If successful, this tea could become an affordable, natural addition to standard diabetes treatment.

The Quick Take

  • What they studied: Whether adding Jinhua dark tea to regular diabetes medications helps people with type 2 diabetes control their blood sugar better than medications alone
  • Who participated: 264 adults aged 40-70 years old with type 2 diabetes from three medical centers in China. The study excluded people with stomach problems or serious diabetes complications
  • Key finding: This is a study protocol (a plan for research), not yet completed results. The main goal is to measure changes in HbA1c (a blood test showing average blood sugar over 3 months) after 6 months of drinking the tea
  • What it means for you: This research hasn’t produced results yet—it’s still being planned and conducted. If the tea proves helpful, it could offer people with diabetes a natural option to use alongside their current medications, though it would not replace prescribed drugs

The Research Details

This is a randomized controlled trial, which is considered one of the strongest ways to test if something actually works. Half of the 264 participants will receive 1 gram of Jinhua dark tea powder mixed with warm water three times daily, while continuing their regular diabetes medications. The other half will receive just warm water with their regular medications. Neither group knows which treatment is “active” versus placebo, though the doctors do know (called an open-label design). Researchers will track participants for 12 months, measuring blood sugar control, cholesterol levels, weight, blood pressure, and other health markers at 6 and 12 months.

Jinhua dark tea is a traditionally fermented tea from China that has been used in folk medicine. Laboratory and animal studies suggested it might help lower blood sugar and improve fat metabolism, but no large human studies had tested this before. This trial is designed to fill that gap by providing solid evidence from real patients.

The study takes place across three medical centers in China, which helps ensure the results apply to different populations and settings. By comparing the tea group to a control group receiving the same medications without the tea, researchers can determine whether any improvements come specifically from the tea itself rather than from the medications or other factors.

This research approach matters because many people with diabetes struggle with their current medications due to side effects or difficulty remembering to take pills. If a natural tea could safely improve blood sugar control, it would give patients another tool. The randomized controlled trial design is important because it’s the most reliable way to prove something actually works—it eliminates bias and shows cause-and-effect relationships rather than just associations

Strengths: This is a large, well-designed study with 264 participants followed for a full year, which provides good statistical power. It measures multiple important health markers, not just blood sugar. The study is registered in a clinical trial database, which increases transparency. Limitations: The study is open-label, meaning participants and doctors know who’s getting the tea, which could create bias. The study only includes people aged 40-70 in China, so results may not apply to younger people or other populations. This is a protocol paper describing the planned study, not actual results yet

What the Results Show

This paper describes the study plan rather than actual findings. The primary outcome being measured is the change in HbA1c (hemoglobin A1c), a blood test that shows average blood sugar control over the previous 2-3 months. Researchers will compare HbA1c levels between the tea group and control group at the 6-month mark.

Secondary outcomes—meaning additional health measures they’ll track—include whether people’s diabetes goes into remission (blood sugar returns to normal range without medication), fasting blood sugar levels, blood sugar levels 2 hours after eating, triglyceride-glucose index (a measure of fat and sugar metabolism), blood pressure, waist circumference, body mass index (BMI), and other metabolic markers. These will be measured at both 6 and 12 months.

The study will help answer whether Jinhua dark tea provides meaningful improvements in blood sugar control and metabolic health when added to standard diabetes treatment. The 12-month duration allows researchers to see both short-term effects (at 6 months) and longer-term sustainability of any benefits.

Beyond blood sugar control, researchers will examine whether the tea affects weight, waist size, blood pressure, and cholesterol levels—all important factors in diabetes management. They’ll also track whether any participants experience diabetes remission, meaning their blood sugar returns to healthy levels. These secondary outcomes help paint a complete picture of the tea’s effects on overall metabolic health, not just glucose control

Previous research on Jinhua dark tea has been limited to laboratory studies and animal experiments, which showed promising results for blood sugar and cholesterol effects. However, what works in a test tube or in mice doesn’t always work in humans. This study is the first large-scale human trial of this tea for diabetes, filling an important gap in the evidence. Other fermented teas and natural products have shown mixed results in human studies, so this research will help determine whether Jinhua dark tea is genuinely effective or whether earlier findings don’t translate to real patients

This is a protocol paper, so actual results aren’t available yet. When results do come out, readers should note: The study is open-label, meaning participants and doctors know who’s receiving the tea, which could influence expectations and outcomes. The study only includes Chinese adults aged 40-70, so results may not apply to younger people, older people, or people from other ethnic backgrounds. The study excludes people with stomach problems or serious diabetes complications, so results may not apply to those populations. The study measures HbA1c at 6 months as the primary outcome, but longer-term effects beyond 12 months remain unknown

The Bottom Line

Wait for study results before making decisions. This is a study protocol, not completed research. Once results are published, people with type 2 diabetes should discuss any interest in Jinhua dark tea with their doctor before trying it. The tea should only be used as an addition to prescribed medications, never as a replacement. Confidence level: Currently low, as this is preliminary research planning. Confidence will increase once actual results are published and reviewed by other scientists

People with type 2 diabetes who are interested in natural approaches to supplement their treatment should follow this research. Healthcare providers treating diabetes patients may find this relevant if results prove positive. People with stomach problems or serious diabetes complications should not participate in this study and should consult their doctor before trying the tea. People without diabetes don’t need this information unless they’re interested in diabetes prevention

The study runs for 12 months per participant, with enrollment across multiple centers. Results likely won’t be published for 1-2 years after the study completes. If the tea does help, benefits would likely appear gradually over weeks to months, not immediately. Blood sugar improvements typically take 4-8 weeks to become measurable

Want to Apply This Research?

  • Track daily HbA1c-related metrics: log fasting blood sugar readings each morning, record blood sugar readings 2 hours after meals, and note any changes in energy levels or diabetes symptoms. If participating in this study, use the app to record tea consumption (3 times daily) and any side effects
  • If this tea becomes recommended, users could set daily reminders to drink the tea at consistent times (morning, midday, evening) with meals. The app could track adherence to both the tea routine and regular diabetes medications, helping users maintain consistency. Users could photograph their tea preparation to build habit consistency
  • Long-term tracking should include weekly blood sugar logs, monthly HbA1c trends (if testing at home), quarterly weight and waist circumference measurements, and ongoing notes about energy levels, hunger patterns, and any side effects. Users should share this data with their healthcare provider during regular check-ups to assess whether the tea is providing real benefits

This article describes a research study protocol, not completed results. Jinhua dark tea has not yet been proven effective for diabetes in human studies. People with type 2 diabetes should not use this tea as a replacement for prescribed medications. Always consult with your doctor or diabetes care team before starting any new supplement or herbal product, especially if you take diabetes medications, as some natural products can interact with drugs or affect blood sugar levels. This information is for educational purposes only and should not be considered medical advice. Results from this study may take 1-2 years to be published and reviewed by the scientific community.