[Significance of nonsaponifiable constituents of dietary fats on the bioactivity of vitamin E]

Abstract

In experiments with male Wistar rats the influence of the non-saponifiable constituents of dietary fats: dl-alpha-tocopherol (60 ppm), dl-gamma-tocopherol (480 ppm), ubiquinone (96 ppm) and beta-sitosterol (3035 ppm) on the tocopherol status was investigated, considering the fatty acid composition of the tested fats. For a test period of eight weeks the animals were fed isoenergetic diets containing three types of dietary fats: corn oil (60% PUFA), a kind of "stripped corn oil" (60% PUFA) and butter (nearly 5% PUFA). Independent of the PUFA-content of the diet, the tocopherol supplementations were able to stabilize the erythrocyte membrane; the calculated hemolysis rates were about 2%. The absence of tocopherols in the diets ("stripped corn oil", butter) caused an increase of the hemolysis rate up to 70% after two weeks. The original amounts of tocopherols in corn oil tended to minimize the hemolysis. Ubiquinone and beta-sitosterol did not reduce the hemolysis rates when they were applied without tocopherols. With respect to creatine-phosphokinase activity, creatine and creatinine excretion the results were similar. Plasma and erythrocyte levels of alpha- and gamma-tocopherol were determined in all groups and discussed in connection with the other examined parameters of tocopherol status. The ultimate result of this experiment is that the content of tocopherols in dietary fats is not always adequate to keep vitamin E status normal, especially if polyunsaturated fatty acid content is high in the diet. Reflecting the vitamin E adequacy of dietary fats, not only alpha-tocopherol but also gamma-tocopherol should be much more considered than previously.