The Vitamin K Dilemma

Vitamin K is a nutrient found in the small intestine where it combines with protein to produce clotting of the blood.  The vitamin is also necessary for the synthesis of proteins found in plasma, bone and the kidneys. A recent prospective study of vitamin K intake and hip fractures found that low intakes of the vitamin might increase the risk of hip fracture in women.  There is a concern, however, for those who are on a specific blood thinning medication.  Here is some insider information on vitamin K.

Should I pay attention to the vitamin K in my diet?

If you have just started taking the blood thinning drug warfarin (also known as Coumadin) as prescribed by your physician, you should become knowledgeable about which foods are high in vitamin K because it might affect the way your warfarin (Coumadin) works.

How much vitamin K do I need from my diet?

The average daily intake of vitamin K in the adult diet is between 60 to 200 micrograms (mcg). The recommended daily intake is 90 mcg for women and 120 mcg for men.

What foods are high in vitamin K?

Deep green vegetables, like spinach, kale and collard greens, contain the highest amounts of vitamin K. A variety of other fruits and vegetables also make the high list (see list below). Liver, bacon and butter are also good sources of this vitamin, but you should avoid them because of their high cholesterol and fat content. Certain oils, such as soybean, canola, cottonseed and olive oil are higher in vitamin K than peanut, corn, safflower and sesame oil. Because salad dressings, margarines, mayonnaises, cakes and pastries can be prepared with a variety of oils, be sure to check the food ingredients label to determine what type of oil(s) are in the foods you are eating. Remember, no matter which oil you choose, all are high in fat and should only comprise a small part of your diet.

Should I avoid foods rich in vitamin K?

The amount of vitamin K it takes to interfere with the anticoagulant effect of warfarin is unknown and very little information is available to substantiate an amount. Unless your diet is unusually high in vitamin K, it does not appear necessary to limit dietary intake of vitamin K when taking warfarin, unless your physician specifies otherwise. Sufficient clinical reports support the importance of keeping your daily intake of vitamin K consistent¹ to improve the stability of warfarin’s blood thinning effect.

Do not make major changes in your diet without notifying your physician! If you become ill and your diet deviates from normal intake, make sure to inform your physician so that your medication can be adjusted. To help you keep a steady intake of the plant foods that contain vitamin K, use the list below to identify the foods that are high, moderate and low in this vitamin. When choosing foods moderate to high in vitamin K content, try to limit your portions of vegetables to small amounts equal to a half of a cup cooked or one cup raw. Include these foods daily to allow for a steady amount of dietary vitamin K intake and reduction of food/drug interaction possibilities.

Should I avoid vitamin K supplements?

Most multivitamins contain insignificant amounts of vitamin K and most likely not enough to cause any interaction with warfarin.  However, as with all nutritional supplements, it is best to speak with your physician before beginning anything new.

You can receive additional information and discover a more detailed list
of Vitamin K containing food items by logging on to http://www.coumadin.com/consumer/INT_VitaminK1.asp.

Foods High in Vitamin K :

Food Moderately High in Vitamin K:

Foods Low in Vitamin K:

References:

1 Cushman M et al., The association of vitamin K status with warfarin sensitivity at the onset of treatment, Br. J Haematol, 2001; 112:572.

 

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