Article contents
Green tea extract only affects markers of oxidative status postprandially: lasting antioxidant effect of flavonoid-free diet*
Published online by Cambridge University Press: 09 March 2007
Abstract
Epidemiological studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease and cancer. The objective of the present study was to investigate the effect of green tea extract (GTE) used as a food antioxidant on markers of oxidative status after dietary depletion of flavonoids and catechins. The study was designed as a 2×3 weeks blinded human cross-over intervention study (eight smokers, eight non-smokers) with GTE corresponding to a daily intake of 18·6 mg catechins/d. The GTE was incorporated into meat patties and consumed with a strictly controlled diet otherwise low in flavonoids. GTE intervention increased plasma antioxidant capacity from 1·35 to 1·56 (P<0·02) in postprandially collected plasma, most prominently in smokers. The intervention did not significantly affect markers in fasting blood samples, including plasma or haemoglobin protein oxidation, plasma oxidation lagtime, or activities of the erythrocyte superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase. Neither were fasting plasma triacylglycerol, cholesterol, α-tocopherol, retinol, β-carotene, or ascorbic acid affected by intervention. Urinary 8-oxo-deoxyguanosine excretion was also unaffected. Catechins from the extract were excreted into urine with a half-life of less than 2 h in accordance with the short-term effects on plasma antioxidant capacity. Since no long-term effects of GTE were observed, the study essentially served as a fruit and vegetables depletion study. The overall effect of the 10-week period without dietary fruits and vegetables was a decrease in oxidative damage to DNA, blood proteins, and plasma lipids, concomitantly with marked changes in antioxidative defence.
Keywords
- Type
- Research Article
- Information
- Copyright
- Copyright © The Nutrition Society 2002
Footnotes
The study has been carried out with financial support in part from a Danish Food Technology grant (FØTEK2, 'Antioxidants from plants') and in part from the Commission of the European Communities, Agriculture and Fisheries (FAIR) specific RTD programme, CT 95-0158 'Natural Antioxidants from Foods'. It does not necessarily reflect its views and in no way anticipates the Commission's future policy in this area.
References
- 81
- Cited by