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
- 1Research Center, Suntory, Osaka, Japan
- 2Department of Food and Nutrition, Providence University, Taichung, Taiwan
- 3Chorng Kuang Hospital, Miaoli, Taiwan
- 4School of Medicine, University of Tokushima, Tokushima, Japan
- 5Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, Beltsville, Maryland
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.
Footnotes
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Address correspondence and reprint requests to Shigeru Yamamoto, PhD, Applied Nutrition Laboratory, Department of Nutrition, School of Medicine, the University of Tokushima, 3 Kuramoto, Tokushima City 770-8503, Japan. E-mail: syamamoto{at}nutr.med.tokushima-u.ac.jp.
Received for publication 24 November 2002 and accepted in revised form 4 March 2003.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
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