Warfarin (Coumadin®) is a very common anticoagulant medication and certain foods and nutrients may affect its absorption. Anyone using warfarin needs to monitor food choices. Recent studies have raised concern about cranberry and warfarin interaction. The results of the largest study to date assessing this potential interaction, conducted in 2009, showed no clinical relevant interaction between cranberry juice and warfarin. Therefore, available evidence suggests that normal daily consumption of four to eight ounces of cranberry juice does not pose a clinically significant risk of interacting with warfarin. It is important to note that cranberries have proven to be beneficial in areas such as preventing urinary tract infections and the adhesion of certain bacteria that can cause stomach ulcers and periodontal gum disease. At this time, warfarin users do not need to completely eliminate cranberry juice from their diet, but dietary recommendation will be based on the individual and will ultimately be the physician’s discretion.
This summary was adapted by Katy Dyer, RD from the “Evidence for Safety: Cranberries and Warfarin” article appearing in the Summer 2010 Wellness/CV Connection Newsletter written by Samina Riaz RD, CDN. SCAN members can log in to the website and access the original article here: http://www.scandpg.org/wellness-and-weight-management/newsletters/
1. Ansell J, McDonough M, Yanli Z, et al. The absence of an interaction between warfarin and cranberry juice: A randomized, double blind trial. J Clin Pharmacol. 2009;49:824-830.
2. Li Z, Seeram NP, Carpenter CL, et al. Cranberry does not affect prothrombin time in male subjects on warfarin. J Am Diet Assoc. 2006;106:2057-2061.
3. United States Department of Agriculture, Nutrient Data Laboratory. Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods 2007. Available at: http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/ORAC/ORAC07.pdf. Accessed February 20, 2010.
4. United States Food and Drug Administration. Drug Details: Coumadin. Available at: http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm?fuseaction=Search.DrugDetails. Accessed September 18, 2009.
5. Lilija JJ, Backman JT, Neuvonen, PJ. Effects of daily ingestion of cranberry juice on the pharmacokinetics of warfarin, tizanidine, and midazolam-probes of CYP2C9, CYP1A2, and CYP3A4. Clin Pharmacol Ther. 2007;81:833-839.
6. Lo E, Nicolle L, Classen D, et al. Strategies to prevent catheter associated urinary tract infections in hospitals. Infect Control Hosp Epidemiol. 2008;29:S41-S50.
7. Reed J. Cranberry flavanoids, atherosclerosis, and cardiovascular health. Crit Rev Food Sci Nutr. 2002;42: 301-316.