Kale is the superfood. It is unquestionably one of the healthiest and most nutrient-dense plant foods available. Kale has four times the vitamin C content of spinach and twice the selenium content, as well as vitamins E and beta-carotene. All of these are essential for maintaining a healthy immune system. Many of the minerals that our modern diets lack are found in kale. It's a good source of calcium from plants, which is essential for strong bones and teeth. Kale is also high in vitamin K, which, according to research, works in tandem with vitamin D to support healthy bone metabolism.