Vitamin K is a fat-soluble vitamin essential for proper blood clotting. In fact, the "K" stands for koagulation, a variant of the word coagulation, which is another term for clotting. Bacteria, including those found in your intestinal tract, are also able to synthesize the vitamin. There is no RDA for vitamin K, but 75 to 140 mcg are recommended as an adequate level. The lower level assumes one half of the estimated requirement comes from bacterial synthesis, whereas the upper figure assumes no bacterial synthesis. Vitamin K is found in plant and animal foods. The richest sources are leafy green vegetables.
Vitamin K Sources
Vitamin K is found in a variety of foods. Plant-based sources include cabbage and cauliflower. Animal-based foods that contain vitamin K include egg yolk and liver. Foods highest in vitamin K are green vegetables, especially the dark, leafy variety. Kale, spinach, mustard greens, turnip greens, collard greens, parsley and Swiss chard are all high in vitamin K. Broccoli, lettuce and Brussels sprouts are among the foods that are moderately high. Vegetable oils, including olive, soybean and canola oils, are additional sources.
Vitamin K Rich Diets
Vitamin K rich diets exceed the adequate intake level for the vitamin, which is at least 75 mcg per day. Because of the high vitamin K concentration of green vegetables, any diet that features these foods will be rich in vitamin K. For example, 1 cup of raw spinach provides 180 percent of the daily value for vitamin K; 1/2 cup of boiled kale provides over 650 percent of the daily value.
Vitamin K Interactions
Vitamin K-rich diets can suppress the function of certain medications. For example, warfarin, also known as Coumadin, is a medication prescribed for those with a tendency to form blood clots. Warfarin inhibits the role of vitamin K in the synthesis of clotting proteins, effectively thinning the blood. Under a doctor's supervision, those who take warfarin, such as heart disease patients, reduce consumption of vitamin K-rich foods.
Vitamin K Deficiency
True vitamin K deficiency is unusual because your intestinal flora are able to synthesize it. However, if the bacterial population in your gut is decreased, for example by antibiotics, the amount of bacterial-derived vitamin is depressed. If adequate amounts are not obtained in the diet, hypoprothrombinemia may result. This condition is characterized by a tendency to bleed and usually warrants vitamin K injection. Of note, newborns have sterile intestines and cannot initially synthesize vitamin K. For this reason it is recommended that newborns receive a single intramuscular dose of the vitamin.
References
- "Biochemistry"; Pamela C. Champe; 2005
- Linus Pauling Institute at Oregon State University: Micronutrient Information Center: Vitamin K
- Office of Dietary Supplements: National Institutes of Health: Important Drug and Food Information: Coumadin
Member Comments