Kale is a crisp and hearty vegetable, with a hint of earthiness. Kale is considered a superfood (meaning it is nutrient-dense while being very low in calories) and packs more nutrition than almost any other whole food.1? Like other dark green leafy vegetables, kale is high in calcium, beta-carotene, and vitamin C, but surpasses other greens with its skyrocketing levels of vitamins A and K.