Much like kale, the leaves of mustard greens are packed with nutrients and antioxidants. Mustard greens have very high levels of vitamins K, A, and C, as well as folate and the mineral manganese. The greens have actually more vitamin A, carotenes, vitamin K, and flavonoid anti-oxidants than some of the more commonly consumed fruits and vegetables. The flavor of the greens have a distinctly peppery taste, adding a bit of a bite to salads, sautés, and the like. Spicy, crunchy mustard greens are one of the most nutritious green-leafy vegetables.