Effects of megadoses of dietary vitamin E on the antioxidant status of rats fed lard or salmon oil

This study was undertaken to investigate whether megadoses of vitamin E in the diet of rats can have pro-oxidative activity. Two experiments with rats were conducted in which both the dietary vitamin E concentration (Experiment 1: 100; 500; 3000; 10,000 mg all-rac-alpha-tocopheryl acetate/kg, and Experiment 2: 100; 1000; 10,000 mg all-rac-alpha-tocopheryl acetate/kg) and the type of dietary fat (lard vs. salmon oil) were varied. Experimental parameters were the concentrations of thiobarbituric acid-reactive substances, 7beta-hydroxycholesterol, the activities of several antioxidative enzymes, the concentration of glutathione in the liver, and the lag time during copper-induced low-density lipoprotein (LDL) oxidation. Increasing the dietary vitamin E concentration to 10,000 mg all-rac-alpha-tocopheryl acetate/kg led to a significant reduction of thiobarbituric acid-reactive substances in the liver after feeding salmon oil, and also to a significant reduction in 7beta-hydroxycholesterol after feeding both dietary fats. Megadoses of vitamin E (3000 and 10,000 mg all-rac-alpha-tocopheryl acetate/kg) also led to a reduction in the activity of superoxide dismutase and the concentration of glutathione in the liver of rats fed salmon oil. The lac, time during LDL oxidation was independent of the dietary vitamin E concentration. The study shows that megadoses of vitamin E, far from having pro-oxidative activity, actually increase the antioxidative capacity of the liver, especially after ingestion of salmon oil.