Although your body can make the fat-soluble vitamin D with sufficient sun exposure, this isn't the case with vitamin K. However, as with vitamin D, you don't necessarily get all of your vitamin K from food. Bacteria in your intestines make at least some of the vitamin K you need, although experts aren't sure exactly how much.
Some of the best sources of vitamin K are green leafy vegetables, including kale, spinach, turnip greens, dark green lettuce, parsley, watercress and Swiss chard. Other sources include broccoli, cauliflower, cabbage, soybeans, green tea, beef liver, cereals and canola, olive and soybean oils.
The adequate intake for vitamin K depends on your age. For infants up to 6 months old, 2 micrograms per day of vitamin K is sufficient, and for those between 7 months and 12 months old, 2.5 micrograms per day is recommended. Children between 1 and 3 years old need 30 micrograms of vitamin K per day, those between 4 and 8 years old need 55 micrograms per day, those between 9 and 13 years old need 60 microgram per day and those between 14 and 18 years old need 75 micrograms per day. Adult women should consume 90 micrograms per day of vitamin K, while adult men need 125 micrograms.
Vitamin K is important for blood clotting and bone mineralization, and may also play a role in cell growth, according to the Linus Pauling Institute. If you switch from using fats high in saturated fat to using oils containing unsaturated fat, you may increase your vitamin K intake while lowering your risk for heart disease.
Vitamin K interacts with certain drugs, including blood thinners such as warfarin. If you take antibiotics for a long time, they may kill off the bacteria in your intestines that make vitamin K, making you mildly deficient in this vitamin if you don't consume enough vitamin K-rich foods, although this is a relatively rare problem.