Iodine deficiency is the world’s single greatest cause of preventable mental retardation. It is especially damaging during the early stages of pregnancy and in early childhood. In their most severe form, iodine deficiency disorders (IDD) include cretinism, stillbirth and miscarriage, and increase infant mortality. Even mild deficiency can cause a significant loss of learning ability – about 13.5 intelligence quotient points at population level – as well as other symptoms such as goitre, an abnormal enlargement of the thyroid gland (Bleichrodt and Born 1994). In addition to infringing on the rights of children, iodine deficiency results in a loss of economic productivity and slows progress towards achievement of the Millennium Development Goals. The good news is that it is easily preventable.