Kale is a form of cabbage and one of the oldest varieties that was first grown in the Mediterranean. It is a type of 'cooking greens' which means they are green and leafy vegetables that are often too bitter to be eaten raw and should be cooked to take the bitterness out. Though greens in general are nutritious foods, kale stands above the rest. Kale is one of the  best sources of beta-carotene - an antioxidant believed by many nutrition experts to be a major player in the battle against cancer, heart disease, and certain age-related chronic diseases. Kale is also an excellent source of nutrients, especially vitamin A and calcium. It's high fiber content helps fill you up and to keeps you full for a good amount of time.