Green tea extract decreases plasma malondialdehyde concentration but does not affect other indicators of oxidative stress, nitric oxide production, or hemostatic factors during a high-linoleic acid diet in healthy females

Background: Green tea contains polyphenolic catechins which can act as anti oxidants and thus decrease the risk for cardiovascular diseases. Aim of the study: To investigate whether green tea extract differs from pla cebo in its effects on markers of antioxidant status, lipid peroxidation, n itric oxide production, thromboxane production, and blood coagulation durin g a controlled high linoleic acid diet in healthy subjects. Methods: Twenty healthy nonsmoking females (23-50 years) participated in a 4-week controlled intervention study. The experimental diet was rich in lin oleic acid (9 en%) and contained fat, protein, and carbohydrates: 27, 14, a nd 59 en%, respectively. In addition, the subjects ingested encapsulated gr een tea extract (3 g/d) or placebo mixture in a double-blind manner. Fastin g blood samples and five 24-hour urines were collected before and at the en d of the 4-week experimental period. Same samples were received from 10 con trol subjects. Results: Green tea extract significantly decreased plasma malondialdehyde ( MDA) concentration in comparison with the placebo treatment. The treatments did not differ in serum lipids, indicators of antioxidant status, urinary 8-isoprostaglandin F-2 alpha, 2,3-dinorthromboxane B-2, nitric oxide metabo lites or coagulation indicators. Conclusions: We conclude that an amount of green tea extract which correspo nds to 10 cups of tea per day for 4 weeks does not have specific effects on several indicators related to risk of cardiovascular diseases in compariso n with placebo treatment. The relatively small but significant decrease in lipid peroxidation indicated by decreased plasma MDA was not associated wit h changes in markers of oxidative stress (urinary 8-isoprostaglandin F-2 al pha and blood oxidized glutathione) or hemostasis.