Kosen-cha, a Polymerized Catechin-Rich Green Tea, as a Potential Functional Beverage for the Reduction of Body Weight and Cardiovascular Risk Factors: A Pilot Study in Obese Patients.

Previous studies have shown that green tea catechins (GTCs) have beneficial effects on obesity and metabolic syndromes. In this study, we prepared kosen-cha from green tea using high pressure extraction, to reduce the astringent taste of the green tea. We identified a large quantity of polymerized GTCs in kosen-cha. To investigate the effects of kosen-cha containing polymerized GTCs in obese Japanese patients, we designed an open-label pilot study in which 6 obese subjects (body mass index (BMI) >25 kg/m²) were administered kosen-cha (5 g/L/d) for 12 weeks. Body composition, serum lipids, insulin resistance, vascular functions, and cardiac hypertrophy were measured before and 12 weeks after kosen-cha administration. Kosen-cha showed no significant adverse effects on the patients. Body weights, BMI, waist circumferences, serum triglyceride (TG) levels, and homeostasis model assessment as an index of insulin resistance (HOMA-IR) levels were significantly decreased after the 12 weeks of administration. Flow-mediated dilation (FMD) (p = 0.0214), brachial-ankle pulse wave velocity (baPWV)(p = 0.0141), left ventricular mass indexes (p = 0.0120), and plasma brain natriuretic peptide (BNP) (p = 0.0144) were significantly improved. Overall, kosen-cha reduced obesity and improved insulin resistance, vascular function, and cardiac hypertrophy, indicating its preventive potential in obesity and metabolic syndrome.