In vivo antioxidant effect of green tea H Sung 1 , J Nah 1 , S Chun 1 H Park 2 , SE Yang 1 and WK Min 1 * 1 Department of Clinical Pathology, Asan Medical Center and University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea; and 2 Department of Clinical Pathology, Kangbuk Samsung Hospital and Sungkyunkwan University School of Medicine, 108 Pyung-dong, Jongro-ku, Seoul 110-102, Korea Objective: The object of this study was to investigate the in vivo antioxidant effect of green tea and dosage effect of green tea on antioxidant effect. Design: We tested 10 healthy subjects (aged 23 – 25 y, five women and five men) with overnight fasting. The total antioxidant capacity of plasma was measured at baseline and 60 min and 120 min after ingestion of 150 ml green tea. Green tea was prepared by infusing 2.5 g of dried green tea leaves for 2 min at 80  C in 150 ml of water. In the second week, they took 300 ml of tea (5.0 g of green tea leaves) and, in the third week, 450 ml of tea (7.5 g of green tea leaves). The total antioxidant capacities of plasma were determined with a Total Antioxidant Kit (Randox Laboratories Ltd, UK) using a Cobas Mira analyser (Roche Diagnostic Systems Inc., Switzerland). The mean intra-assay coefficient of variation was 1.2%. Results: The total antioxidant capacity of plasma increased by 1.1% at 60 min and 2.1% at 120 min over baseline value in subjects consuming 150 ml of green tea, which was statistically not significant. However, total antioxidant capacity of plasma after consuming 300 ml of green tea showed a significant increase of 7.0% after 60 min and 6.2% after 120 min (P < 0.0001), and after consuming 450 ml 12.0% after 60 min and 12.7% after 120 min over baseline value (P < 0.0001). Conclusions: Total antioxidant capacity of plasma was significantly increased after taking green tea in amounts of 300 and 450 ml. A positive increment according to green tea dosage was also observed. Sponsorship: This work was funded by the Pacific Corporation (Korea). Descriptors: antioxidant effect; green tea; polyphenol; dosage European Journal of Clinical Nutrition (2000) 54, 527–529 Introduction Oxidative damage by oxygen free radicals are known to be one of the mechanisms of chronic disorders such as atherosclerosis or cancer (Halliwell & Gutteridge, 1989). Oxygen free radicals are created through aerobic meta- bolism and are mostly removed by antioxidants in vivo (Diplock, 1994). Three groups of antioxidants in vivo prevent oxidative damage. Superoxide dismutase, gluta- thione peroxidase and metal-binding proteins are primary antioxidants that prevent the formation of new free radicals. Secondary antioxidants such as vitamins C and E, beta carotene, uric acid, bilirubin and albumin prevent the cascade of oxidative reactions by combining with free radicals. Tertiary antioxidants such as DNA repair enzyme and methionine sulphoxide reductase repair the oxidative damage. There are several reports that argue that long-term intake of vitamin supplements of vitamins C and E or beta carotene prevent chronic disorders caused by oxidative damage (Barber & Harris, 1994; Gaziano et al, 1992; Rimm et al, 1993; Stampfer et al, 1993; Verlangieri et al, 1985). Not only vitamin supplements but also drinks that contain high levels of antioxidants could prevent chronic disorders (Bushman, 1998; Hertog et al., 1993). Red wine is one of the best known such drinks (Maxwell et al, 1994; Whitehead et al, 1995), and the green tea favored by Orientals also contains high level of antioxidants. A few epidemiologic studies have reported that the incidence of coronary heart disease and cancer decreased with intake of green tea (Bushman, 1998; Kohlmeier et al, 1997; Stoner & Mukhtar, 1995) and that the oxidation of low density lipoprotein was suppressed with green tea in vitro (Luo et al, 1997). However, the studies dealing with in vivo increase of antioxidant effects of green tea are rare (Benzie et al, 1999; Pietta et al, 1998; Serafini et al, 1996). As there is no report that explain the increment in antioxidant effect according to the volume of green tea, the authors carried out this study to elucidate the dosage effect of green tea on antioxidants in vivo. Methods Human subjects This study was approved by the Ethical Committee of the Asan Medical Center. The study subjects were 10 healthy adult volunteers (five women and five men). All of them were free of clinical, biochemical or haematological man- ifestations of cardiovascular, hepatic, renal or endocrine disorders. Before the study they were instructed to avoid drinking green tea for one week, otherwise to keep to their normal diet. They came to the laboratory in the morning after overnight fasting. *Correspondence: Dr WK Min, Department of Clinical Pathology, Asan Medical Center and University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea. E-mail: wkmin@www.amc.seoul.kr Guarantor: WK Min. Contributors: WKM was the lead investigator and the person mainly responsible for all stages of the study. HS carried out the study and wrote the paper. JN and SC supervised all aspects of the study. HP and SEY assisted with the experimental design and the statisitical analysis of data. All investigators were involved in preperation and subsequent revision of the paper. Received 24 August 1999; revised 26 December 1999; accepted 11 January 2000 European Journal of Clinical Nutrition (2000) 54, 527–529 ß 2000 Macmillan Publishers Ltd All rights reserved 0954–3007/00 $15.00 www.nature.com/ejcn