Vitamin K May Actually Benefit Warfarin-Treated Patients
A small study presented at Nutrition 2019 suggests that vitamin K intake may be beneficial in some patients receiving the anticoagulant warfarin.1
These findings are somewhat contradictory to the common belief that patients receiving anticoagulant therapy should limit their intake of vitamin K, which promotes coagulation.2 Patients on anticoagulants like warfarin are often advised to avoid vitamin K-containing vegetables like kale, spinach, cabbage, broccoli, and collards, as well as foods like soybean oil, strawberries, and whole milk.2
However, according to lead study author Guylaine Ferland, PhD, professor of nutrition at Université de Montréal and scientist at the Montreal Heart Institute Research Centre in Canada, vitamin K intake could be safe in this patient population as long as intake levels remain stable.
“I think all warfarin-treated patients would benefit from increasing their daily vitamin K intake. 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,” explained Dr Ferland in a press release.3
Dr Ferland and colleagues arrived at their conclusion after performing a 24-week randomized controlled trial of 49 participants aged 32 to 85 years at the Anticoagulation Clinics of the Montreal Heart Institute and the Jewish General Hospital in Montreal.
Participants included in the study had been receiving anticoagulation therapy for more than 6 months with a target international normalized ratio (INR) range of 2.0 to 3.0 or 2.5 to 3.5 and had also presented a %TTR of less than 50% within the past 6 months.
Each participant was randomly assigned to either the vitamin K intervention group (n = 28) or a control group (n = 21). In the intervention group, participants were advised to increase their vitamin K consumption to at least 150 µd/day. Dietary counsel on specific food choices, recipes, and cooking strategies was provided. In the control group, patients received a similar amount of general dietary information.
Ultimately, 50% of patients in the intervention group had achieved the primary clinical outcome of anticoagulation stability, or %TTR of at least 70%, from weeks 4 through 24 compared with 19% of controls. Mean %TTR was 67.7 for the intervention group and 61.4 for the control group throughout the assessment period.
With these findings in mind, Dr Ferland and colleagues concluded that warfarin-treated patients may not need to avoid vitamin K completely. In fact, warfarin-treated women and men may benefit from consuming a minimum of 90 mcg and 120 mcg per day, respectively, from food sources, Dr Ferland added.3
“Our hope is that healthcare professionals will stop advising warfarin-treated patients to avoid green vegetables,” said Dr Ferland in a press release.3
1. Ferland G, Chahine S, Presse N, et al. Increasing dietary vitamin K intake stabilizes anticoagulation therapy in warfarin-treated patients with a history of instability: a 24-week randomized controlled trial. Paper presented at: Nutrition 2019; June 11, 2019; Baltimore, MD.
2. Vitamin K. Medline Plus. https://medlineplus.gov/vitamink.html. Page last reviewed April 24, 2019. Accessed June 11, 2019.
3. Eating more vitamin K found to help, not harm, patients on warfarin [press release]. Baltimore, MD. American Society for Nutrition. June 11, 2019. Accessed June 11, 2019.