Vitamin K Helps, Not Harms Patients on Warfarin

A new clinical trial suggests that patients on warfarin benefit from increasing their vitamin K intake, as long as they keep their intake levels consistent.

Warfarin is often used to prevent blood clots that cause heart attacks and strokes, and its dosage must be calibrated to balance the risk of clots against the risk of uncontrolled bleeding. Since warfarin counteracts the activity of vitamin K in the blood, large swings in vitamin K intake can disrupt this balance. Providers often suggest that patients limit their intake as a result.

In the first randomized controlled trial to test how patients on warfarin respond to dietary intervention, the researchers analyzed 46 patients with a history of anticoagulation instability. Approximately half of the patients attended dietary counseling sessions and cooking lessons that provided general nutrition information, while the other half attended counseling sessions and cooking lessons focused on increased intake of green vegetables and vitamin-K rich oils and herbs.

After 6 months, 50% of those counseled to increase their vitamin K intake were maintaining stable anticoagulation levels compared with just 20% of those who received the general nutritional counseling, a significant improvement.

The results indicate that patients would be better advised to increase the amount of vitamin K in their diet by consuming foods that provide a minimum of 90 micrograms of vitamin K per day for women and 120 micrograms per day for men.

"I think all warfarin-treated patients would benefit from increasing their daily vitamin K intake,” lead study author Guylaine Ferland, said in a press release. "That said, given the direct interaction between dietary vitamin K and the action of the drug, it is important that (higher) daily vitamin K intakes be as consistent as possible."

Reference

• Ferland G, Chahine S, Presse N, et al. OR36-04-19 — Increasing dietary vitamin k intake stabilizes anticoagulation therapy in warfarin-treated patients with a history of instability: A 24-week randomized controlled trial. https://www.eventscribe.com/2019/ASN/fsPopup.asp?Mode=presInfo&PresentationID=545052. Presented at: Nutrition 2019. June 8-11, 2019. Baltimore, Maryland.
• Eating more vitamin K found to help, not harm, patients on warfarin [press release]. EurekAlert Website. Published June 11, 2019. https://www.eurekalert.org/pub_releases/2019-06/asfn-emv053019.php. Accessed June 11, 2019.