Vitamin K is a nutrient that is necessary to maintain healthy bones. It serves as a coenzyme, or a necessary helper, for the production of proteins that aid in both blood clotting and bone metabolism. Vitamin K is found in abundance in leafy vegetables like collards, turnip greens, spinach, and kale. It is also found in broccoli. Smaller amounts are found in soy, carrot juice, canned pumpkin, pomegranate juice, and okra. The best natural source of vitamin K that has the greatest amount of this vitamin is a fermented soybean dish, otherwise known as natto. Vitamin K interferes with blood-thinning medication like warfarin. Follow your doctor's dietary instructions if you are taking blood thinners.