Effect of dietary protein on vitamin E levels in erythrocytes and tissues of rats.

The effect of dietary protein level on the transfer of alpha-tocopherol in blood to tissues including RBC was studied using rats. The first experiment comprised a 10% casein (low protein), 20% casein (normal) and 20% SPI (normal soybean protein) diet groups supplemented with 71.5 mg of alpha-Toc/kg diet. In Exp. 2 the relationship of the tissue alpha-Toc level and protein level in diets, as shown by recovery from vitamin E-deficient status after the administration of alpha-Toc for 3 days, was checked by adjusting the protein level in diets to 10%, 20% and 40% casein. In Exp. 1 alpha-Toc in RBC decreased significantly in the 10% casein and 20% SPI groups compared to the 20% casein group. Moreover, alpha-Toc in kidney, lung and muscle decreased significantly in the 10% casein and 20% SPI groups. alpha-Toc in liver in the 20% SPI group decreased significantly compared to the 20% casein group. In Exp. 2 similar results were observed (Table 4), but alpha-Toc in RBC showed only a tendency to decrease with the low protein diet. In Exp. 1 free cholesterol in RBC increased significantly in the 10% casein group compared with the other two groups.