Vitamin K is a fat soluble vitamin that is important for blood clotting and bone formation. Naturally occurring forms of vitamin K vary by plant and animal sources. Vitamin K1, the form synthesized by plants, is one of the richest sources providing on average over 100 ug of vitamin K per 100g serving.
Vitamin K in Vegetables
Vitamin K that comes from plant sources is called phylloquinone. Leafy green vegetables, such as kale, lettuce, broccoli, spinach, and seaweed are good sources. Other vegetables higher in vitamin K include cauliflower, legumes and canola, along with soybean, olive and cottonseed oils. Green teas made from sweet clover or tonka beans, soybeans and natto are also vitamin K rich foods.
Bioavailability
Food sources like vegetables generally have low rates of absorption and utilization. Since vitamin K is a fat soluble vitamin, absorption can be increased by moderate intakes of fat. A tablespoon of salad dressing on a leafy green salad can accomplish this effectively.
Cooking and freezing do not affect bioavailability, however exposure to light and hydrogenation will affect how the body absorbs and uses this nutrient.
Nutrient Medication Interactions
The function of warfarin can be affected by vitamin K intake. Anticoagulant medications inhibit an enzyme that helps recycle vitamin K. It can cause a deficiency of vitamin K, and frequently there is confusion surrounding vitamin K intake when taking such medications. Individuals taking blood thinning medications such as warfarin should keep their daily intake of vitamin K constant.
References
- "Vitamin K Background;" Dietitians of Canada; 2008
- "Krause's Food, Nutrition and Diet Therapy;" L.K.Mahan, S. Escott-Stump; 2004
- "Modern Nutrition in Health and Disease;" Shils et al.; 2006
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