Background: Black tea is known to have protective effects against plasmalipid and lipoprotein oxidation, but its influence on lipid peroxidation in tissue has been less studied.The effect of oral black tea consumption on protein oxidation has also not been demonstrated. The presentstudy investigated the antioxidant effects of oral black tea consumption. Material/Methods: Male Sprague-Dawleyrats were fed a regular murine chow diet. The controls were supplied with water ad libitum, while theblack tea group received aqueous black tea extract as the sole source of liquids. At the end of the ten-weekexperimental period, intestinal brush border, liver and kidney reduced-glutathione concentrations wereevaluated as an index of cellular antioxidant defence. Plasma and tissue malondialdehyde concentrationsand plasma protein carbonyl content were measured to evaluate lipid peroxidation and protein oxidation,respectively. Results: The plasma malondialdehyde and protein carbonyl contents of rats consuming theblack tea were significantly less than in controls. Similarly, liver and kidney malondialdehyde concentrationswere significantly lower in the experimental group, while jejunoileal mucosa were not affected. Ten weeksof black tea administration caused significantly higher reduced-glutathione levels in the kidneys ofblack tea-administered rats, and a significant negative correlation was observed between kidney malondialdehydeand glutathione concentrations. Conclusions: These findings provide evidence that long term black teasupplementation is capable of protecting both plasma proteins and plasma lipids from oxidative injury,and demonstrate that chronic black tea administration protects both liver and kidney tissues - but notthe jejunoileal mucosa - against oxidation.

Keywords: Thiobarbituric Acid Reactive Substances - analysis, Tea - chemistry, Reference Standards, Random Allocation, Plant Extracts - pharmacology, Malondialdehyde - blood, Administration, Oral, Liver - drug effects, Lipids - blood, Lipid Peroxidation - drug effects, Kidney - drug effects, Glutathione - analysis, Blood Proteins - drug effects, Antioxidants - pharmacology