A nutritional powerhouse, kale contains high amounts of several vitamins and minerals. Of note is its hefty vitamin K content. Vitamin K is responsible for blood-clotting, which means that it may interact with medications meant to thin the blood. If you're on such a medication, be sure to speak with your doctor about how much kale you can safely consume.
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Kale's Vitamin K Content
Like most green leafy vegetables, kale is a rich source of vitamin K. One cup of chopped raw kale contains 472 micrograms of the vitamin. This is far more than 100 percent of the adequate intake for adults, which is 90 micrograms for women and 120 micrograms for men. Cooked kale is an even richer source; 1 cup offers over 1,062 micrograms. That's more than 10 times the adequate intake for women.
Problems With Too Much K
For healthy people, getting too much vitamin K isn't a problem. Vitamin K is a fat-soluble vitamin, which means that excess is stored in the body, but no known toxicity risks occur from taking in too much. If you have a condition that requires you to take blood-thinning medications such as warfarin, however, excessive intake of vitamin K or fluctuations in the amount you consume each day through diet and supplements can inhibit the effectiveness of your medication and lead to complications.
What to Do
Be sure to talk to your doctor about your specific situation. The Linus Pauling Institute recommends that people taking anti-coagulants stick to the adequate intake for vitamin K and keep their intake levels steady. This means you'll have to limit your intake of kale, especially if you eat other vitamin K-rich foods throughout the day. Other foods high in vitamin K include other leafy greens such as spinach and collard greens, as well as brussels sprouts, broccoli and asparagus. If kale is your only source, you can have about 1/4 cup of the raw vegetable in a day.
Other Benefits of Kale
Including some kale in your diet is a good thing. Kale is a rich source of the antioxidants lutein and zeaxanthin, which support your eyesight. It's also rich in the antioxidant beta-carotene, which can potentially boost immunity and prevent diseases such as cancer. If you're a vegetarian who avoids dairy, you should know that kale is one of the richest vegetarian sources of calcium, which you need for strong bones.