Your body requires vitamin K, also called phylloquinone, to produce a series of proteins called coagulation factors. When activated, these proteins form blood clots to stop bleeding. The vitamin K your body requires comes almost exclusively from vegetables, fruits and nuts in your diet. The level of vitamin K in different vegetables varies broadly, ranging from none to amounts that greatly exceed your daily intake requirements.
Role in Health
Vegetables with high levels of vitamin K support the production of the coagulation factors. Without adequate amounts of dietary vitamin K, your body may produce abnormally low levels of the coagulation factors, potentially leading to a tendency to bleed or bruise easily. Vitamin K-rich vegetables may also support the normal mineralization of your bones, which keeps them strong and resistant to fractures. Consuming vegetables that contain high levels of vitamin K helps prevent you from developing a vitamin K deficiency, which occurs uncommonly in the United States.
Vitamin K-Rich Vegetables
Green leafy vegetables contain the highest levels of vitamin K. For example, a cup of cooked kale provides you with approximately 1,145 micrograms of vitamin K, roughly 10-times the adequate daily intake level recommended by the Institute of Medicine. Examples of the vitamin K content in a cup of other cooked vegetables rich in this micronutrient include boiled spinach, 990 to 1,045 micrograms; turnip greens, 850 micrograms; collards, 835 micrograms; beet greens, 695 micrograms; mustard greens, 420 micrograms; Brussels sprouts, 220 to 300 micrograms; broccoli, 160 to 220 micrograms; and cabbage 165 micrograms. Iceberg lettuce and raw spinach provide you with 130 micrograms and 145 micrograms of vitamin K per cup, respectively.
Vitamin K-Poor Vegetables
Knowing what vegetables contain low levels of vitamin K can help you manage your nutrition plan with respect to this micronutrient. Mushrooms and corn, for example, contain no measurable amount of vitamin K. Trace to low-level amounts of vitamin K are found in onions, radishes, beets, turnips, water chestnuts, potatoes, navy beans, parsnips, pumpkin, eggplant, sweet potatoes, lentils, zucchini, yellow squash, tomatoes and peppers.
Medical Considerations
Familiarizing yourself with the vitamin K levels in various vegetables is particularly important if you take the blood-thinning medication warfarin. Warfarin reduces the activity of vitamin K in your body and interferes with the production of certain coagulation factors. Taken in an appropriate dosage, warfarin reduces the likelihood of formation of harmful bloods clots in your body and slows the formation of normal clots. Eating large amounts vegetables with high levels of vitamin K can overwhelm the warfarin in your system, rendering the medication ineffective. When taking warfarin, consume approximately the same amount of vitamin K each day to keep the levels of warfarin and vitamin K in your body balanced. Because green, leafy vegetables contain the highest levels of vitamin K, keep the number of servings of these vegetables you eat daily at a constant level to help ensure ongoing effectiveness of your warfarin therapy.
References
- Food and Agriculture Organization of the United Nations: Human Vitamin and Mineral Requirements, Vitamin K
- Oregon State University Linus Pauling Institute: Vitamin K
- U.S. Department of Agriculture National Nutrient Database: Vitamin K (Phylloquinone) (mcg) Content of Selected Foods per Common Measure
- Institute of Medicine of the National Academies, Food and Nutrition Board: Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals
- National Institutes of Health: Important Information to Know When You are Taking Coumadin and Vitamin K
- "Chest"; Oral Anticoagulants: Mechanism of Action, Clinical Effectiveness, and Optimal Therapeutic Range; Jack Hirsh, M.D., et al.; January 2001
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