Effects of Jinhua instant dark tea in patients with type 2 diabetes mellitus: study protocol for a multicenter, open-label, randomized controlled trial.

BACKGROUNDS: The global prevalence of diabetes is rising, with many patients experiencing challenges in medication adherence and adverse effects associated with synthetic drugs. Natural products have attracted interest as potential preventive or adjunctive therapies. Jinhua dark tea (JHTea), a naturally fermented Chinese tea, has shown promising glucose-lowering and lipid-modulating effects in vitro and animal studies, but robust clinical evidence is lacking. This study is the first large-scale, long-term randomized controlled trial (RCT) evaluating JHTea as an adjunctive therapy for type 2 diabetes mellitus (T2DM). METHODS: This multicenter, open-label parallel randomized controlled trial across three centers in China will enroll 264 participants aged 40-70 years with T2DM, excluding those with gastrointestinal diseases or acute diabetes-related complications. Participants will be randomized 1:1 to the following: (1) intervention Group: 1 g of JHTea three times daily plus current oral hypoglycemic agents for 12 months. (2) control Group: warm water plus current oral hypoglycemic agents alone, with no extra active intervention. The primary outcome is the change in hemoglobin A1c (HbA1c) at 6 months. Secondary outcomes at 6 and 12 months include diabetes remission rate, fasting plasma glucose (FPG), 2-h postprandial glucose, triglyceride-glucose index (TyG), blood pressure, abdominal circumference, body mass index (BMI), and other metabolic parameters. DISCUSSION: This study aims to investigate the glycemic and lipid-modulating effects of Jinhua instant dark tea in patients with T2DM. The findings may support the adjunctive role of fermented Jinhua tea in diabetes management, providing a complementary strategy to conventional therapies. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2400080339. Registered on 26 January 2024. https://www.chictr.org.cn/showproj.html?proj=214179.