Trace elements are minerals which the body only needs in small (trace) amounts. Elements which are present in the body with less than 50 milligrams per kilogram of body weight are therefore known as trace elements. Iron is an exception, it slightly exceeds the defined upper limit, but is still one of the trace elements. Besides iron, also zinc, selenium, copper, iodine, fluoride, manganese, chromium and molybdenum are trace elements. Trace elements are important for healthy development. The body needs iodine for the formation of thyroid hormones, iron for blood formation, zinc for the normal function of the immune system, and fluoride for healthy teeth.