Four years away from a self-imposed target date for the eradication of iodine deficiency disorder, China remains the world's most affected country. Preventing iodine deficiency is simple—many countries do so by adding iodine to salt—and the penalties for ignoring the problem are immense, said experts. Chinese government figures show that about 10 million Chinese suffer some form of mental retardation because of iodine deficiency disorder.
Iodine, the 53rd element in the periodic table, is a key ingredient in thyroxine, a hormone produced in the thyroid gland. When a pregnant woman's diet lacks iodine, her fetus may suffer inadequate brain development because thyroxine production is inhibited. Thyroxine promotes complex brain development and thus directly affects an infant's intelligence. Although iodine is a critical nutritional supplement, very little of the substance—about 0.001 g (0.02 grain) each day—is required to prevent iodine deficiency disorder.
Persons born with below-normal brain development due to an absence of thyroxine sometimes suffer severe mental retardation. The most extreme form of iodine deficiency disorder is cretinism, a condition characterized by severe mental retardation accompanied by physical deformities. If treated in early infancy, cretinism may be cured with lifelong iodine supplements.
Many persons with iodine deficiency disorder do not exhibit overt signs of retardation, however. Although these people suffer decreased intelligence, their intelligence quotient (IQ) may not be low enough for them to be defined as retarded. Iodine deficiency can also cause goiter, a disease that causes enlargement of the thyroid gland; deafness; and miscarriages.
The World Health Organization (WHO) has reported that more than 400 million Chinese live in areas where iodine in the soil is not sufficient for nutritional needs. Inland areas in China tend to be iodine deficient, due mainly to alluvial and glacial activity that has reduced the iodine content of the soil. Plants grown in such soil lack sufficient iodine, and so iodine does not enter the human diet.
One of the measures China took to address the problem was to require that all salt sold in the country be iodized, a task that has proven difficult to achieve. Although salt from government sources is largely iodized, black market salt is usually not. Because black market salt is often less expensive, many Chinese buy it instead of the iodized salt produced by the government.
In 1991 Chinese Premier Li Peng said that China would eradicate iodine deficiency disorder by the year 2000. The government has sponsored awareness programs, such as National Iodine Day, and has been assisted in these efforts by a variety of international aid agencies, such as the United Children's Fund (UNICEF), WHO, and the United Nations Development Program (UNDP).
Many other regions of the world also suffer from iodine deficiency disorder, including Africa, the Middle East, and South America. In the United States the disorder was once common in the Great Lakes region—an area once referred to as the goiter belt.