Say hello to the Hulk of all superfoods! The reason this mean green is so popular? It's delicious, versatile, and incredibly nutritious. Kale contains beta-carotene and the antioxidants lutein and zeaxanthin—which are associated with eye health—as well as potassium, vitamin A, vitamin C, fiber, iron, and calcium. Plus, you get 2 grams of protein in a serving. Consider using kale as a stand-in for spinach in dishes, or try out some of these recipes.