Coumadin is an anticoagulant and blood thinner prescribed to people who are at risk of developing blood clots. One of its main drug-nutrient interactions is with vitamin K. Changing your dietary intake of vitamin K will alter the effect of Coumadin -- sudden increases may decrease its effect, while greatly lowering your intake can increase it. Vitamin K-2 is simply one of the naturally occurring forms of vitamin K.
Coumadin's Mechanism of Action
Vitamin K is an essential player in the blood clotting process. It catalyzes the carboxylation of certain protein residues that are required for blood coagulation. Coumadin inhibits clotting by interfering with some of these vitamin K-dependent reactions, thereby resulting in the undercarboxylation of glutamic acid. This interferes with the coagulation cascade, lengthening the time it takes for a clot to form.
Dietary Recommendations
As a result, the Clinical Center of the National Institutes of Health Drug-Nutrient Interaction Task Force recommends that in order to maintain a therapeutic effect for Coumadin and ensure that it works effectively, it is important to keep your intake of vitamin K foods as consistent as possible. So, if you eat foods containing vitamin K as part of your normal diet, continue to do so in moderation. Refrain from eating excessive amounts of vitamin K-rich foods. The Clinical Center suggests limiting intake of foods considered "high" in vitamin K to no more than one serving per day and foods "moderately high" to no more than three servings per day.
Food Sources
Green, leafy vegetables, including kale, spinach, turnip greens, collards, Swiss chard, parsley and mustard greens are rich sources and are considered "high" in vitamin K. "Moderately high" foods are Brussels sprouts, green leaf lettuce, broccoli, endive and Romaine lettuce. Other sources are cranberry juice, alcohol, green tea, chickpeas, lentils, soybeans, canola oil, mayonnaise and pistachio nuts.
Other Considerations
When Coumadin is given to pregnant women, it may interfere with the newborn's vitamin K synthesis, placing him at increased risk of a vitamin K deficiency. Also, according to Drugs.com, perinatal administration of Coumadin may result in other problems, such as central nervous system defects, spontaneous abortion, stillbirth and hemorrhage. It is therefore contraindicated during pregnancy. The manufacturer also recommends that nursing women exercise caution when taking Coumadin, even though Coumadin has not been detected in human milk.
References
- National Institutes of Health Drug-Nutrient Interaction Task Forc: Clinical Center:
- Linus Pauling Institute, Oregon State University: Vitamin K
- USDA National Nutrient Database for Standard Reference, Release 17: Vitamin K Content
- "Drugs"; Current concepts and controversies in the use of vitamin K; JA Thorp, L Gaston, DR Caspers, ML Pal; March 1995.
- Drugs.com: Warfarin Pregnancy and Breastfeeding Warnings
