Vitamin K, a fat-soluble vitamin, plays an important role in blood clot formation. The liver uses vitamin K to make prothrombin, the protein that causes blood clotting. While this is normally beneficial, people who take blood thinners, such as warfarin or heparin, can develop excessive bleeding if they take in too much vitamin K. Since many vegetables contain vitamin K, people taking blood thinners limit their intake of vegetables high in vitamin K.
Daily Allowance
The recommended daily allowance of vitamin K is 65 mcg for women and 80 mcg for men, Frank Jackson, M.D. of Jackson/ Siegelbaum Gastroenterology reports. Most of the vitamin K you need comes from diet, although bacteria in the intestine also produce a small amount of vitamin K. The National Institutes of Health recommends eating no more than one serving of vegetables high in vitamin K per day and no more than three servings of vegetables with moderate levels.
Vegetable Types
Green leafy vegetables contain the largest amount of vitamin K in the vegetable family. Kale contains the highest amount, followed by Swiss chard, collard greens, spinach, Brussels sprouts and watercress and endive. Green scallions, broccoli, cabbage and mustard greens also contain a full day's supply of vitamin K, Dr. Jackson reports. While parsley also contains large amounts of vitamin K, you're unlikely to eat this garnish in the amounts required to exceed your daily limit.
Amounts of Vitamin K
One cup of raw kale contains 540 mcg of vitamin K per cup, while 1/2 cup of cooked collard greens contains 440 mcg and 1/2 cup of cooked spinach contains 360 mcg. Five Brussels sprouts supply 289 mcg and 1/2 cup cooked broccoli 113 mcg. Coleslaw and cooked cabbage both contain around 100 mcg per serving. Seven asparagus spears supply 80 mcg, about one day's worth of vitamin K, Dr. Jackson states.
Keeping a Food Diary
Keeping a food diary can help pinpoint the amount of foods you can eat without having an effect on your tendency to bruise or bleed excessively, Dr. Jackson recommends.
Staying Consistent
The National Institutes of Health recommends keeping your vitamin K intake consistent rather than avoiding foods containing vitamin K altogether, since a sudden increase or decrease can interfere with your blood's clotting ability.
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