For a simple grass you can easily grow at home, wheatgrass generates a lot of buzz. Some proponents claim it can cure everything from the common cold to cancer, but there is no scientific evidence to support those claims. Even so, drinking the juice as a nutritional supplement is a good way to get essential vitamins, including a substantial dose of vitamin K. Because of its high vitamin K content, certain people, including those who take the anti-coagulant medication warfarin, should speak to their doctor before consuming wheatgrass.
All About Vitamin K
Vitamin K is a fat-soluble vitamin, which means your body stores excess amounts in the liver and in fatty tissue. The vitamin's main role is to support proper blood coagulation. Bacteria in your intestines make a small amount of vitamin K, and you also get it form your diet. The best sources of the vitamin are green vegetables rich in chlorophyll, the plant pigment that produces vitamin K. Kale, turnip greens, broccoli, spinach, asparagus and wheatgrass are all rich sources.
Vitamin K in Wheatgrass
The daily value for vitamin K is 80 micrograms. A small 4-gram serving of wheatgrass contains 35 micrograms of vitamin K, which is 44 percent of the daily value. This is a moderate amount, but some powdered wheatgrass juice supplements can contain as much as 160 percent of the DV for vitamin K.
Vitamin K and Warfarin
People who take warfarin need to keep their vitamin K intakes as consistent as they can. Suddenly increasing your vitamin K intake by drinking wheatgrass juice can decrease the effectiveness of warfarin and increase your risk of developing a blood clot. The National Institutes of Health advises people who take warfarin to limit their intake of of foods that contain moderate amounts of vitamin K -- between 60 percent and 199 percent of the DV -- to three servings per day. Wheatgrass is considered a supplement and not a food, however. NIH cautions those who take warfarin to avoid supplements that list vitamin K on the label unless they have a doctor's permission.
Other Potential Issues With Vitamin K
According to the University of Maryland Medical Center, vitamin K has few side effects at recommended intake levels. Wheatgrass can provide more than the recommended intake, however. As such, pregnant and breast-feeding women should not take wheatgrass without a doctor's consent. Vitamin K crosses the placenta and is present in breast milk. Others who should not consume wheatgrass without their doctor's consent include those taking antibiotics, especially cephalosporins, phenytoin, orlistat and olestra, and certain cholesterol-lowering medications.