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Influence of dietary vitamin K intake on subtherapeutic oral anticoagulant therapy
Author(s) -
Rombouts Eva K.,
Rosendaal Frits R.,
Van Der Meer Felix J. M.
Publication year - 2010
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/j.1365-2141.2010.08108.x
Subject(s) - medicine , vitamin , hazard ratio , confidence interval , vitamin d and neurology , vitamin k antagonist , vitamin k , vitamin k2 , gastroenterology , physiology , endocrinology , warfarin , atrial fibrillation
Summary It is unclear what advice should be given to patients using vitamin K antagonists with respect to dietary vitamin K intake. We performed a nested case–control study in patients attending a Dutch anticoagulation clinic, to determine the association between vitamin K intake and subtherapeutic International Normalized Ratio (INR) values and the interaction between usual and recent vitamin K intake. Compared to patients with a normal usual vitamin K intake, those with a high vitamin K intake had a decreased risk of a subtherapeutic INR [Hazard Ratio (HR) 0·80, 95% confidence interval (CI): 0·56–1·16] and patients with a low vitamin K intake an increased risk (HR 1·33, 95% CI: 0·79–2·25). In patients with a low usual vitamin K intake, recent vitamin K intake was twice as high in cases as in controls (164 vs. 85 μg/d). Such a difference was not observed in patients with a normal or high usual vitamin K intake. Our results suggest that a high vitamin K intake reduces the risk of a low INR by lessening the influence of incidental consumption of vitamin K rich food on the INR. These findings support the recommendation for patients on vitamin K antagonists to eat a sufficient amount of vitamin‐K containing foods.