Importance of iron regulation- Excretion

The human body needs iron for oxygen transport. That oxygen is required for the production and survival of all cells in our bodies. Human bodies tightly regulate iron absorption and recycling. Iron is such an essential element of human life, in fact, that humans have no physiologic regulatory mechanism for excreting iron. Most humans prevent iron overload solely by regulating iron absorption. Those who cannot regulate absorption well enough get disorders of iron overload. In these diseases, the toxicity of iron starts overwhelming the body's ability to bind and store it. ^[2]

http://en.wikipedia.org/wiki/Human_iron_metabolism#Importance_of_iron_regulation

Despite the fact that iron is the second most abundant metal in the earth's crust, iron deficiency is the world's most common cause of anemia. When it comes to life, iron is more precious than gold. The body hoards the element so effectively that over millions of years of evolution, humans have developed no physiological means of iron excretion. Iron absorption is the sole mechanism by which iron stores are physiologically manipulated.


http://sickle.bwh.harvard.edu/iron_absorption.html