The Importance of Iodine in Everyday Diet

Feb 10, 2011
Michael Koger

Fruit - Reprinted with permission from Centers for Disease Control

Iodine is an essential nutrient throughout life for humans, and deficiency may lead to serious medical complications.

Iodine is a trace element which occurs naturally in some foods and through fortification in others. It has been present in table salt in the United States since the 1920s, and this has virtually resolved the problem of iodine deficiency disease there. The use of iodized salt is inexpensive, simple, and effective for the prevention of iodine deficiency anywhere in the world. Some vitamin and mineral supplements also contain iodine.

During the last 20 years, iodization of salt has taken place in many other countries through the efforts of the World Health Organization, the United Nations Children’s Fund, the salt industry, and the International Council for the Control of Iodine Deficiency Disorders. More than 70 countries have implemented universal salt iodization, and this covers two-thirds of the world’s population.

Prevalence of iodine deficiency

Iodine deficiency, however, is still prevalent in Europe, Southeast Asia, Africa, Eastern Mediterranean, Western Pacific, and the Americas. Although 70 percent of households worldwide use iodized salt, nearly one-third of school age children on the globe do not. This poses a serious public health problem because pregnant women, infants, and children are especially at risk for the consequences of iodine deficiency when it occurs.

Worldwide, iodine deficiency is still a public health problem in 47 countries. Mountainous regions tend to be the most iodine deficient because the soil there contains insufficient amounts of the mineral. As a result, the crops have very little iodine to offer humans who consume them. Furthermore, animals that eat those crops will be deficient in this trace element, and humans who consume meat will not obtain much iodine from it.

Hence, iodine deficiency was endemic in mountainous areas of the United States and Mexico and regions close to the Great Lakes prior to the use of iodized salt. Today the most iodine deficient parts of the world are the Himalayas, Alps, and Andes where mountain ranges are present. Moreover, river valleys prone to floods, such as in South and Southeast Asia, tend to become iodine insufficient areas.

Most salt intake in the United States is from processed foods, and that salt has usually not undergone iodization. Iodine is available, however, in seaweed and many other foods. Seaweed includes kelp, nori, kombu, and wakame. It is also present in seafood, dairy products, grain products, and eggs. Breast milk and infant formulas also have iodine.

Pregnancy and breastfeeding

Iodine deficiency is the most common cause of preventable mental retardation worldwide. If the mother is deficient in iodine during pregnancy, there may be neurodevelopmental problems and below average intelligence quotient in the child. This is particularly true if the deficiency is severe enough that the mother’s thyroid gland enlarges and becomes a goiter.

It may also lead to attention-deficit hyperactivity disorder in the child. There may also be stillbirth, miscarriage, or cretinism when the mother is iodine deficient during pregnancy. Cretinism is a serious and irreversible form of mental retardation which results from iodine deficiency and still occurs in Africa and Asia today. Children and pregnant women in low income countries are especially at risk for health problems when there is iodine deficiency.

Since iodine has an important role in the synthesis of thyroid hormone or thyroxine, the mother’s requirement during pregnancy increases. The fetus has not yet developed his or her thyroid gland and must therefore depend on the mother’s supply of iodine and thyroxine. In other words, if the mother does not consume enough iodine during pregnancy, or any other time in her life, she will not make enough thyroid hormone.

Many prenatal multivitamin supplements in the United States do not have iodine, and some pregnant or breastfeeding mothers do not take iodine supplementation. However, some studies suggest that iodine supplementation is not necessary for women who are pregnant or breastfeeding if the geographic area where she lives is iodine sufficient. Nevertheless, some organizations recommend iodine supplementation for the mother during pregnancy and breastfeeding and for the child during the first several years of life.

In areas of the world where iodized salt is not always available, the World Health Organization recommends iodine supplementation for all women of childbearing age.

The best way to obtain enough iodine is through a well-balanced diet, and this trace element absorbs nearly 100 percent via the gastrointestinal tract. Mothers who exclusively breastfeed their child must still supply enough of the mineral to the baby. Regardless of whether iodized salt is available, the mother should give the baby complementary foods which contain iodine when she weans the infant from breastfeeding.