Antihyperglycemic Effect of Oolong Tea in Type 2 Diabetes
Kazuaki Hosoda, BS1, Ming-Fu Wang, PHD2, Mei-Ling Liao, MS2, Chin-Kuang Chuang, MD3, Miyuki Iha, BS4, Beverly Clevidence, PHD5 and Shigeru Yamamoto, PHD4
1 Research Center, Suntory, Osaka, Japan
2 Department of Food and Nutrition, Providence University, Taichung, Taiwan
3 Chorng Kuang Hospital, Miaoli, Taiwan
4 School of Medicine, University of Tokushima, Tokushima, Japan
5 Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, Beltsville, Maryland
OBJECTIVE—To determine the efficacy of oolong tea for lowering plasma glucose in type 2 diabetic patients in Miaoli, Taiwan.
RESEARCH DESIGN AND METHODS—A total of 20 free-living subjects who had type 2 diabetes and took hyperglycemic drugs as prescribed were enrolled in the present study. Subjects consumed oolong tea (1,500 ml) or water for 30 days each in a randomized crossover design. Tea was not consumed for 14 days prior to treatments.
RESULTS—Relative to initial concentrations, oolong tea markedly lowered concentrations of plasma glucose (from 229 ± 53.9 to 162.2 ± 29.7 mg/dl, P < 0.001) and fructosamine (from 409.9 ± 96.1 to 323.3 ± 56.4 µmol/l, P < 0.01), whereas the water control group had not changed (208.7 ± 61.0 vs. 232.3 ± 63.1 mg/dl for glucose and from 368.4 ± 85.0 to 340.0 ± 76.1 µmol/l for fructosamine).
CONCLUSIONS—Oolong tea may be an effective adjunct to oral hypoglycemic agents in the treatment of type 2 diabetes.
Abbreviations: HPLC, high-performance liquid chromatography
OOlong Tea Increases Plasma Adiponectin Levels
Olong tea increases plasma adiponectin levels and low-density lipoprotein particle size in patients with coronary artery disease
Kenei Shimada, , a, Takahiko Kawarabayashib, Atsushi Tanakab, Daiju Fukudaa, Yasuhiro Nakamuraa, Minoru Yoshiyamaa, Kazuhide Takeuchia, Tetsuya Sawakic, Kazuaki Hosodac and Junichi Yoshikawaa
a Department of Internal Medicine and Cardiology, Graduate School of Medicine, Osaka City University Medical School, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan
b Department of Cardiology, Baba Memorial Hospital, Sakai, Japan
c Suntory Research Center, Suntory Ltd., Osaka, Japan
Revised 15 January 2004; accepted 21 January 2004. Available online 16 March 2004.
Background: Oolong tea has been studied for its effect on cardiovascular disease and obesity. Plasma adiponectin levels are reduced in obesity, in patients with type 2 diabetes mellitus and in coronary artery disease (CAD). Objective: To investigate prospectively, whether intake of Oolong tea influences plasma adiponectin levels, low-density lipoprotein (LDL) particle size, total cholesterol, high-density lipoprotein (HDL) cholesterol, LDL cholesterol, serum triglyceride and plasma glucose levels in patients with CAD. Methods: Twenty two patients in our study consumed Oolong tea (1000 ml) or water for 1 month in our randomized cross-over study design. Results: There was a significant difference in plasma adiponectin levels before and after 1 month intake of Oolong tea (6.26±3.26 μg/ml versus 6.88±3.28 μg/ml, P<0.05), and in plasma level LDL particle size (25.02±0.67 nm versus 25.31±0.60 nm, P<0.01). The water-consuming control group showed no changes (6.28±3.28 μg/ml versus 6.23±3.21 μg/ml) in adiponectin levels or LDL particle sizes (25.03±0.70 nm versus 25.02±0.72 nm). We also observed a significant difference in hemoglobin A1c levels (7.23±4.45% versus 6.99±4.30%, P<0.05) before and after intake of Oolong tea. Conclusion: Oolong tea may have beneficial effects on the progression of atherosclerosis in patients with CAD.
Author Keywords: Oolong tea; Adiponectin; Small dense LDL; Coronary artery disease; Diabetes mellitus