Myth: Vitamin K should not be consumed while on anticoagulation drugs such as Warfarin (Coumadin).
Contrary Research
-
1: Blood. 2007 Mar 15;109(6):2419-23. Epub 2006 Nov 16.
-
- Comment in:
- Blood. 2007 Apr 15;109(8):3607; author reply 3607-8.
- J Fam Pract. 2008 Apr;57(4):following 220.
Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin.
School of Clinical and Laboratory Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.
Patients receiving warfarin who have unstable control of anticoagulation have a significantly lower intake of dietary vitamin K compared with their stable counterparts. We hypothesized that supplementation with oral vitamin K would improve stability in patients with previously unstable control of anticoagulation. Seventy warfarin-treated patients with unstable anticoagulation control were randomly assigned in a double-blinded fashion to receive a daily amount of 150 mug oral vitamin K or placebo orally for 6 months. Measures of stability of anticoagulation control in the 6-month study period were compared with those in the 6 months immediately prior to it. Vitamin K supplementation resulted in a significantly greater decrease in standard deviation of international normalized ratio (INR) compared with placebo (-0.24 +/- 0.14 vs -0.11 +/- 0.18; P < .001) and a significantly greater increase in percentage time within target INR range (28% +/- 20% vs 15% +/- 20%; P < .01). Anticoagulation control improved in 33 of 35 patients receiving vitamin K supplementation; of these, 19 fulfilled our criteria for having stable control of anticoagulation. However, only 24 of 33 patients receiving placebo demonstrated some degree of improvement, with only 7 patients fulfilling the criteria for having stable control. Concomitant supplementation of vitamin K, perhaps through reducing the relative day-to-day variability in dietary vitamin K intake, can significantly improve anticoagulation control in patients with unexplained instability of response to warfarin.
PMID: 17110451