Antihyperglycemic Effect of Oolong Tea in Type 2 Diabetes

Abstract

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.