Kale is a vegetable in the species Brassica oleracea, which contains broccoli, cauliflower, collard greens, and Brussels sprouts. Kale has green or purple leaves, in which the central leaves do not form a head. There are many varieties of kale, classified by leaf type, including curly-leaved (Scots Kale), plain-leaved, rape kale, leaf and spear (a cross between curly-leaved and plain-leaved kale), and cavolo nero (also known as black cabbage, Tuscan Cabbage, Tuscan Kale, Lacinato and dinosaur kale). Classification
Like so many vegetables, kale comes to us from the Middle East via Europe, and U.S cultivation of kale started around 1800.
Kale is very high in beta carotene and vitamins K and C, and high in calcium. Kale contains two carotenoids, lutein and zeaxanthin, and sulforaphane, another antioxidant. Kale is also rich in antioxidant flavonoids, particularly kaempferol and quercitin.
Kale, like the other cruciferous vegetables, is a dietary source of sulfur-containing glucosinolates, which produce cancer-protective isothiocyanates as breakdown products.
Kale and other greens are rich in iron and calcium. Unfortunately, only a small percentage of these minerals is absorbed due to the presence of oxalate, which binds them and decreases their bioavailability.
Kale is high in alpha-linolenic acid (ALA), an essential omega-3 fatty acid.