Our last column explained the role of iodine in the body and its importance as a nutrient in foods. New research indicates that iodine intake has been declining in the United States and a variety of emerging health problems may be related.
Don't we get plenty of iodine in salt?
Probably not. In the U.S., only about 20 percent of the salt is iodized. Virtually none of the salt added to prepared and fast-food products is iodized. Many of us have stopped adding salt to food at the table, cutting iodine intake as a consequence.
Concerns are further bolstered by tests of iodized salt in the U.S. that find lower iodine levels than is recommended. Other key foods previously high in iodine now have lower levels. For example, the iodine content of milk and bread has greatly declined due to changes in methods of production.
What health problems may be related to declining iodine intake?
In adults, low iodine intake can lead to impaired thyroid function. The result is fatigue and a host of other health problems. Poor thyroid function also is likely aggravated by low intake of iron and selenium. The greater iron needs of women may contribute to the higher incidence of thyroid problems among women.
But the greatest concern exists for infants and children. The small thyroid gland in a newborn infant contains only about 24 hours worth of iodine. Consequently, infants need a fresh supply from mother's milk or formula on a daily basis. Iodine is critical for normal nerve development.
Both cerebral palsy and impaired hearing may be associated with poor iodine nutrition during early infancy. Also, studies report links between iodine deficiency and attention deficit hyperactivity disorders in children. Increased incidence of ADHD has paralleled a national decline in iodine intake. A cause-effect relationship remains to be established and low iron status may also contribute to ADHD.
How much iodine is recommended?
Recommended daily intake for adults is 150 micrograms. The recommendation climbs to 220 mcg per day in pregnancy and 290 mcg per day during breastfeeding. The U.S. upper limit for adults is 1,100 mcg per day.
Iodine intake is of special concern for women during pregnancy and breastfeeding to provide proper nourishment to the fetus and baby. This is so important that concerned iodine researchers from Texas ended a scientific article on iodine with the statement, "... if we have the right to have children, do children have a right to be born with their full potential?"