Open AccessVitamin E and K interactions – a 50‐year‐old problem
Author(s) -
Traber Maret G
Publication year - 2008
Publication title -
nutrition reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.958
H-Index - 150
eISSN - 1753-4887
pISSN - 0029-6643
DOI - 10.1111/j.1753-4887.2008.00123.x
Subject(s) - vitamin , vitamin k2 , clotting factor , enzyme , metabolism , chemistry , vitamin d and neurology , endocrinology , excretion , medicine , biochemistry , biology
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 ω‐hydroxylates the K 1 side chain, thereby preventing its β‐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.