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Title: Genoprotective effects of green tea (Camellia sinensis) in human subjects : results of a controlled supplementation trial
Authors: Han, KC
Wong, WC
Benzie, IFF 
Keywords: DNA
Comet assay
Oxidative stress
Green tea
Functional food
Issue Date: Jan-2011
Publisher: Cambridge University Press
Source: British journal of nutrition, Jan. 2011, v. 105, no. 2, p. 171–179 How to cite?
Journal: British journal of nutrition 
Abstract: Green tea is rich in polyphenolic antioxidants and has widely reported but largely unsubstantiated health benefits. In the present study, genoprotective effects of two types of green tea were studied both in an in vitro and in a human supplementation trial. For the in vitro study, human lymphocytes were pre-incubated in tea (0·005–0·1 %, w/v), washed and subjected to oxidant challenge induced by H₂O₂. In a placebo-controlled, cross-over supplementation study, eighteen healthy volunteers took 2 × 150 ml/d of 1 % (w/v) green tea (‘Longjing’ green tea or ‘screw-shaped’ green tea) or water (control) for 4 weeks (n 6). Subjects took all the three treatments in a random order, with 6 weeks' washout between each treatment. Fasting blood and urine were collected before and after each treatment. The comet assay was used to measure the resistance of lymphocytic DNA to H₂O₂-induced challenge. Basal oxidation-induced DNA damage was measured using the formamidopyrimidine glycosylase (Fpg) enzyme-assisted comet assay. Urine 7,8-dihydro-2-deoxyguanosine (8-oxodG, mol/mmol creatinine), a biomarker of whole-body oxidative stress, was measured by liquid chromatography with tandem MS. In vitro testing results of tea-treated cells showed increased (P < 0·05) resistance of DNA to the challenge. In the supplementation trial, a significant (P < 0·05) increase in resistance was also observed. Furthermore, the FPg comet data showed >20 % decrease in DNA damage with tea supplementation: mean and standard deviation changes in %DNA in comet tail in the Fpg-assisted comet assay were: − 5·96 (sd 3·83) % after Longjing tea; − 6·22 (sd 3·34) % after screw-shaped tea; +0·91 (sd 5·79) % after water (P < 0·05). No significant changes in urine 8-oxodG were seen. The results indicate that green tea has significant genoprotective effects and provide evidence for green tea as a ‘functional food’.
ISSN: 0007-1145
EISSN: 1475-2662
DOI: 10.1017/S0007114510003211
Rights: © The Authors 2010
The following article " K. C. Han, W. C. Wong and Iris F. F. Benzie (2011). Genoprotective effects of green tea (Camellia sinensis) in human subjects: results of a controlled supplementation trial. British Journal of Nutrition, 105, pp 171-179. doi:10.1017/S0007114510003211." is available at
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