According to traditional Chinese belief, oolong tea is effective in the control of body weight. Few controlled studies, however, have been conducted to measure the impact of tea on energy expenditure (EE) of humans. A randomized cross-over design was used to compare 24-h EE of 12 men consuming each of four treatments: 1) water, 2) full-strength tea (daily allotment brewed from 15 g of tea), 3) half-strength tea (brewed from 7.5 g tea) and 4) water containing 270 mg caffeine, equivalent to the concentration in the full-strength tea treatment. Subjects refrained from consuming caffeine or flavonoids for 4 d prior to the study. Tea was brewed each morning; beverages were consumed at room temperature as five 300 mL servings. Subjects received each treatment for 3 d; on the third day, EE was measured by indirect calorimetry in a room calorimeter. For the 3 d, subjects consumed a typical American diet. Energy content of the diet was tailored to each subject's needs as determined from a preliminary measure of 24-h EE by calorimetry. Relative to the water treatment, EE was significantly increased 2.9 and 3.4% for the full-strength tea and caffeinated water treatments, respectively. This increase over water alone represented an additional expenditure of 281 and 331 kJ/d for subjects treated with full-strength tea and caffeinated water, respectively. In addition, fat oxidation was significantly higher (12%) when subjects consumed the full-strength tea rather than water.

Marine animals produce astaxanthin which is a carotenoid and antioxidant. In this study we determined the in vitro and ex vivo effects of astaxanthin on LDL oxidation. The oxidation of LDL was measured in a 1 ml reaction system consisting of increasing concentrations of astaxanthin (12.5, 25.0, 50.0 microg/ml), 400 microM V-70 (2, 2'-azobis(4-methoxy-2, 4-dimethylvaleronitrile)), and LDL (70 microg/ml protein). Astaxanthin dose, dependently significantly prolonged the oxidation lag time (31.5, 45.4, 65.0 min) compared with the control (19.9 min). For the ex vivo study 24 volunteers (mean age 28.2 [SD 7.8] years) consumed astaxanthin at doses of 1.8, 3.6,14.4 and 21.6 mg per day for 14 days. No other changes were made in the diet. Fasting venous blood samples were taken at days 0, +14. LDL lag time was longer (5.0, 26.2, 42.3 and 30.7% respectively) compared with day 0 after consuming astaxanthin at doses of 1.8, 3.6,14.4 and 21.6 mg for 14 days compared with day 0, but there was no difference in oxidation of LDL between day 0 (lag time 59.9+/-7.2 min) and day 14 (57.2+/-6.0 min) in the control group. Our results provide evidence that consumption of marine animals producing astaxanthin inhibits LDL oxidation and possibly therefore contributes to the prevention of atherosclerosis.

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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 Ϯ 53.9 to 162.2 Ϯ 29.7 mg/dl, P Ͻ 0.001) and fructosamine (from 409.9 Ϯ 96.1 to 323.3 Ϯ 56.4 mol/l, P Ͻ 0.01), whereas the water control group had not changed (208.7 Ϯ 61.0 vs. 232.3 Ϯ 63.1 mg/dl for glucose and from 368.4 Ϯ 85.0 to 340.0 Ϯ 76.1 mol/l for fructosamine).CONCLUSIONS -Oolong tea may be an effective adjunct to oral hypoglycemic agents in the treatment of type 2 diabetes. Diabetes Care 26:1714 -1718, 2003R ecently, consumption of tea has become even more popular in Taiwan, Japan, and China. Consumption of tea leaves in Taiwan increased 2.2 times during last 20 years (1). Tea consumption may have an impact on plasma glucose concentrations. The concept was supported by in vivo studies of tea fed to diabetic rodents (2-4) and by in vitro studies where tea components were incubated with brush border membrane vesicles of rabbit small intestine (5).Caffeine is one of the most important components in tea. There are some studies examining caffeine, for example, in healthy volunteers (6,7), in type 1 diabetes (8 -10), and in type 2 diabetes (11). However, the efficacy of tea in lowering plasma glucose concentrations in humans was limited.There are three types of tea: green, oolong, and black. They are produced from a single plant species, but they are distinguished by the processing technique. Oolong tea is partially fermented during processing, whereas green tea is not fermented, and black tea is fully fermented (12).In general, the amount of the polymerized polyphenols is determined by the level of the fermentation. The degree of fermentation of oolong tea leaves from Taiwan is very low because of the preparation method. In contrast, oolong tea leaves from China contained an especially large amount of polymerized polyphenols, and fermentation was strong (13). For these reasons, oolong tea from China was used in this study.The purpose of this study was to assess the ability of oolong tea to lower plasma glucose concentrations in subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS -The ethical committee of Providence University, an institutional review board, approved the study, and subjects gave informed consent. A total of 10 men and 10 women (average age 61.2 years, duration of diabetes 4.8 years) were recruited through their physicians at Chorng Kuang Hospital, Miaoli, Taiwan.The study used a crossover design; sex-matched subjects were randomly assigned to treatment order. Subjects were divided into two groups at random. The washout period was set ...