Thyroid & Iodine..What You Should Know-Part 1

Medical Author: Ruchi Mathur, M.D.
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR

Many of my patients ask questions or make comments about iodine use in thyroid disease. Examples are: " Should I increase the iodine in my diet if I'm hypothyroid?" "My mother had hyperthyroidism, and they told her it was because of a lack of iodine." " My sister has thyroid disease, and to avoid getting it, I'm taking Kelp tablets." "Can I eat sushi if I take Synthroid?"

Although these questions and comments are relevant, this subject is peppered with "old wives tales" and folklore. In the first part of this discussion, I'd like to focus on the role iodine in relation to the thyroid gland and its function.... a bit of physiology for the beginner. Later, I will discuss how an excess or deficiency of iodine can contribute to diseases of the thyroid gland.

Why does the body need iodine?

The major function of the thyroid gland is to produce thyroid hormone in an amount sufficient to meet the body's needs. To make thyroid hormone, the thyroid uses iodine. If iodine is not available in the diet, the thyroid may produce an insufficient amount of hormone.

How much iodine does the body need?

Areas in the United States where iodine deficiency occurs are scarce. In North America, iodine is added to salt and bread. It is also present in additives, water sources, medications, and dietary supplements. The daily iodine intake varies widely throughout the world. A minimum of 60 micrograms of elemental iodine per day is required to make thyroid hormone. The following lists examples of average iodine intake in various countries and the recommended amount of iodine consumption:

Typical Iodine Intakes

North America

200-700 micrograms/day


20-150 micrograms/day


50-150 micrograms/day


130-180 micrograms/day