Although many people are aware that the drugs they take can interact with each other, many do not realize that certain nutrients can also interact with medications. Whether the nutrient increases or decreases the drug's effect, the result can be dangerous. The blood thinner Coumadin and vitamin K are one such interacting pair: Vitamin K is an important nutrient, but you must keep your intake consistent when taking Coumadin.
Coumadin
Coumadin -- generic name warfarin -- is an anticoagulant medication prescribed for people at risk for developing blood clots. When you take Coumadin, you lengthen the time it takes your blood to clot. Your doctor will typically usually do a monthly blood test to check how long it takes for your blood to clot, to make sure it stays in the desired range.
Vitamin K
Vitamin K is a fat-soluble vitamin needed for blood clotting and bone health. You get vitamin K in certain foods, and your intestinal bacteria make it. Most people easily get enough vitamin K in their diet, but deficiencies can result from diseases that affect nutrient absorption, including Crohn's disease, celiac disease, cystic fibrosis, gallbladder disease and liver disease. Mild deficiency may also occur if you take antibiotics that kill intestinal bacteria.
If you are at risk for blood clots, obviously vitamin K intake can be a concern, since it helps blood to clot. The dilemma is that you need vitamin K to help the body use calcium; low levels have been associated with low bone density.
Dietary Sources of Vitamin K
For adults, the dietary reference intake -- or DRI -- for vitamin K is 80 mcg daily. A serving of kale contains 660 percent of the DRI, cooked spinach has 560 percent and turnip greens, 530 percent. These foods, along with collard greens, Swiss chard, beet greens, parsley and mustard greens, are considered very high in vitamin K. Foods considered moderately high include Brussels sprouts with 190 percent, raw spinach, 180 percent; turnip greens, 170 percent; and broccoli, 110 percent. Endive, Romaine and green leaf lettuce also contain moderately high amounts. Foods made with the fat substitute Olestra sometimes contain fat-soluble vitamins and should be considered a source of vitamin K.
Balancing Coumadin and Vitamin K
If you take Coumadin, you might think you should avoid foods containing vitamin K. In fact, you need to consume some vitamin K for bone health. What you do need to do, however, is consume about the same amount of vitamin K each week so your doctor can accurately calculate your Coumadin dosage. If you considerably decrease the amount of vitamin K-rich foods you eat after you begin taking Coumadin, you can be at risk of bleeding. If you considerably increase your vitamin K intake, your Coumadin dosage will not be strong enough and you can be at risk of forming blood clots. If your intake of vitamin K does change, notify your doctor.
