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Nutr Rev. 2008 Nov;66(11):624-9. doi: 10.1111/j.1753-4887.2008.00123.x.

Vitamin E and K interactions--a 50-year-old problem.

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Linus Pauling Institute, Department of Nutrition and Exercise Sciences, Oregon State University, Corvallis, Oregon 97331, USA.


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.

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