CHAPTER 18. Interference Effect of Vitamin E on Vitamin K Metabolism

The possibility that excessive vitamin E intake causes vitamin K deficiency bleeding has been recognized for a long time, but the cause is still unknown. We aimed to clarify the influence of vitamin E intake on vitamin K concentration and its physiological activity using rats. Intake of an α-tocopherol-containing diet lowered phylloquinone (PK) concentrations in various tissues except for the liver. α-Tocopherol suppressed the elevation of an extrahepatic PK concentration after oral administration of PK. However, the tissue concentration of menaquinone-4 (MK-4), another vitamin K isoform converted from PK in the body, did not decrease after α-tocopherol intake. Unlike α-tocopherol, intake of a γ-tocopherol-containing diet did not lower PK or MK-4 concentration in tissues, but excess intake of γ-tocopherol significantly decreased PK concentration in some extrahepatic tissues. Excess intake of α-tocopherol did not affect blood clotting activity, uncarboxylated osteocalcin concentration in the serum, bone density, or expression of the gene related to bone metabolism. These results revealed that α-tocopherol intake lowered extrahepatic PK concentration, but this decrease in PK concentration had little effect on vitamin K physiological activity in rats.