Vitamin K helps your body by making proteins for healthy bones and tissues. It also makes proteins for blood clotting. If you don't have enough vitamin K, you may bleed too much. Newborns have very little vitamin K. They usually get a shot of vitamin K soon after they are born. If you take blood thinners, you need to be careful about how much vitamin K you get. You also need to be careful about taking vitamin E supplements. Vitamin E can interfere with how vitamin K works in your body. Ask your health care provider for recommendations about these vitamins.
Most people get their vitamin K from plants such as green vegetables, and dark berries. Bacteria in your intestines also produce small amounts of vitamin K.
Vitamin K helps make four of the 13 proteins needed for blood clotting. Its role in maintaining the clotting cascade is so important that people who take anticoagulants such as warfarin (Coumadin) must be careful to keep their vitamin K intake stable.
Lately, researchers have demonstrated that vitamin K is also involved in building bone. Low levels of circulating vitamin K have been linked with low bone density, and supplementation with vitamin K shows improvements in biochemical measures of bone health. (1) A report from the Nurses’ Health Study suggests that women who get at least 110 micrograms of vitamin K a day are 30 percent less likely to break a hip than women who get less than that. (2) Among the nurses, eating a serving of lettuce or other green, leafy vegetable a day cut the risk of hip fracture in half when compared with eating one serving a week. Data from the Framingham Heart Study also shows an association between high vitamin K intake and reduced risk of hip fracture in men and women and increased bone mineral density in women. (3, 4)
People who do not regularly eat a lettuce salad or green, leafy vegetables are likely to be deficient in their intake of vitamin K; national data suggests that only about one in four Americans meets the goal for vitamin K intake from food. (5)