Kale contains four vitamins considered essential for health including vitamin A, which keeps eyes healthy, and vitamin C, an antioxidant and immune booster. Kale also contains vitamin K, which aids blood clotting, and vitamin B12, also known as folate, a vitamin that is essential to new cell growth and maintaining healthy brain function. Like some types of fish, kale contains omega-3 fatty acid and lutein, which protects the eyes from cataracts.
Minerals in kale include calcium, potassium and zinc, which all have positive benefits for the human body. Calcium is well-known for building strong bones and teeth, but it is also beneficial for keeping blood pressure under control and muscles relaxed. Potassium helps maintain the body's fluid balance and keeps the heart beating steadily. Zinc frees vitamin A from the liver while supporting the body's immune system. Zinc is also an important element in wound healing.
Some varieties of kale have flat green leaves, while others have curly leaves, and one variety has leaves with a bluish tint. While each variety has a different flavor, all varieties of kale have high levels of protein. One cup of kale contains almost 3 grams of protein, but has only 33 calories. That same amount of kale also has 2.5 grams of fiber, making kale a good choice for managing blood sugar.