7/20/2004 - Sarah Booth and colleagues from Tufts University, Boston, US,have discovered that high dose vitamin E supplements can antagonise theeffects of vitamin K, resulting in an anticoagulant effect typical of lowvitamin K status.

High levels of vitamin E supplementation (as alpha-tocopherol) have beenreported to enhance anticoagulant effects in patients taking oralanticoagulants such as warfarin and phenprocoumon. Although it has beenproposed that vitamin E might be responsible for this antagonism byinteracting with vitamin K, this had not been systematically investigatedin humans with a normal baseline coagulation status. Animal data hadsuggested that there might be a critical ratio of vitamin E to vitamin K,such that elevated doses of vitamin E have an anticoagulant effect whenvitamin K intake is low.

This study comprised two trials. The first (study A) involved 38 men andwomen with rheumatoid arthritis, and the second (study B) involved 32healthy men. Both trial groups had normal baseline coagulation status andsubjects were not taking oral anticoagulants. Both trials lasted for 12weeks and involved vitamin E supplementation with 1,000 IU/day. Thebiochemical marker PIVKA-II (proteins induced by vitamin K absence-factorII) was used to assess vitamin K status, with an increase in PIVKA-IIbeing indicative of poor vitamin K status.

In both studies the vitamin E supplemented groups had significantlyincreased plasma vitamin E levels after twelve weeks. This did not changein either placebo group. In both studies baseline vitamin K status wasnormal. PIVKA-II significantly increased from baseline in both vitamin Esupplemented groups, but remained unchanged in the placebo groups. Hencethe authors concluded that high doses of vitamin E did increase PIVKA-IIstatus, which may have been due to an inhibitory effect on vitamin Kactivity. However, they point out that further research is necessary todetermine the mechanism of action involved, and the possible benefits oradverse outcomes of this interaction. (From the American Journal ofClinical Nutrition , 2004, 80 (1):143 - 148).

In a separate but related article, it is also suggested that regulation ofvitamin K is important in patients on coumarin anticoagulants, accordingto a paper in the American Journal of Medicine (2004; 116 : 651-56).Eating too many vitamin K-rich foods led to under-coagulation whiledecreasing their consumption had the opposite effect. Coagulationincreased by day 7 in those whose diets had lowered vitamin K levels andfell by day 4 in those supplemented with vitamin K. The research group areconcerned that the usual advice given to such patients to reduce theirvitamin K intake is not always accurate.

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