Mustard greens are an excellent source of vitamin K, an essential nutrient that is necessary for blood clotting. Vitamin K also supports bone health by helping your blood to transport calcium throughout your body. Mustard greens are also high in vitamin C and E, two powerful antioxidants that help remove free radicals from your body. Sauté mustard greens instead of boiling them to retain their flavor. Combine 1 or 2 cups of mustard greens with 1/2 cup of chopped onions and your favorite seasonings. Enjoy them alone or with your favorite lean meat.