Vitamin E and K interactions--a 50-year-old problem.
The mechanisms by which vitamin E interferes with vitamin K activity, especially blood clotting, are not known, but hypothetically this interference may involve metabolic pathways. Phylloquinone (K(1)) must be converted to menaquinone (MK-4, the most potent extrahepatic tissue vitamin K) by truncation of the K(1) side chain and replacement with geranylgeranyl. Possible mechanisms for the vitamin E and K interaction include: 1) vitamin E competes for the yet undiscovered enzyme that truncates the K(1) side chain; 2) vitamin E competes with K(1) for the hypothetical cytochrome P450 enzyme that omega-hydroxylates the K(1) side chain, thereby preventing its beta-oxidation and its removal for MK-4 formation; or 3) vitamin E increases xenobiotic pathways that increase hepatic metabolism and excretion of all vitamin K forms. Currently, the pathway for K(1) conversion to MK-4 is unknown, the process for regulating vitamin K metabolism to urinary excretion products is unknown, and why vitamin E supplements have such a dramatic effect, causing bleeding in some individuals and not in others, remains a mystery.
Traber
Maret G
MG
Linus Pauling Institute, Department of Nutrition and Exercise Sciences, Oregon State University, Corvallis, Oregon 97331, USA. maret.traber@oregonstate.edu
D001777:Blood Coagulation / Q000187:drug effects* / Q000502:physiology; D004347:Drug Interactions; D006490:Hemostatics / Q000378:metabolism; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D010084:Oxidation-Reduction / Q000187:drug effects; D014810:Vitamin E / Q000378:metabolism*; D014812:Vitamin K / Q000031:analogs & derivatives / Q000378:metabolism*; D024482:Vitamin K 2 / Q000031:analogs & derivatives / Q000378:metabolism; D015262:Xenobiotics / Q000378:metabolism*
D006490:Hemostatics; D015262:Xenobiotics; D024482:Vitamin K 2; D014812:Vitamin K; D014810:Vitamin E; C030814:menatetrenone