Vitamin C is not all that makes citrus fruits so indispensable. Nevertheless, they have such a high vitamin C content that one to two lemons or two to three oranges are sufficient to cover an adult's vitamin C requirements. At the same time, citrus fruits contain a healthy portion of vitamin B - which is important for blood formation and the metabolism - plus valuable minerals such as potassium and calcium. Potassium lowers the blood sugar level and promotes cell growth. Calcium ensures strong bones, healthy teeth and taut skin. The flavonoid content is also an important cell protection factor, protecting the skin against oxidative stress.