Can Iodine Supplements Cause Thyroid Cancer?

New research has found that exposure to radioactive iodine-131 during childhood causes increased risk of thyroid cancer later in life. The research also points to both iodine deficiency and iodine supplementation as important and independent modifiers of this risk. The Journal of the National Cancer Institute for May 18th reports the study findings, which researchers say have important implications.

Investigators write:

"Stable iodine supplementation in iodine-deficient populations may substantially reduce the risk of thyroid cancer related to radioactive iodines in case of exposure to radioactive iodines in childhood that may occur after radiation accidents or during medical diagnostic and therapeutic procedures." In the study, French researcher Dr. Elisabeth Cardis performed a case-control study of 276 thyroid cancer patients and 1300 controls who lived near the Chernobyl nuclear power plant, and were 15 or younger at the time of the Chernobyl accident in the 1980s.

They found that the risk of radiation-related thyroid cancer was three times higher in iodine-deficient areas than in other areas.

According to Dr. John D. Boice Jr., of the International Epidemiology Institute in Rockville, Maryland and Vanderbilt University in Nashville, Tennessee, these new findings provide "new and, if confirmed, provocative information on the risk of radiation-induced thyroid cancer and on the modifying role of diets deficient in stable iodine and of administering iodine supplements months after the exposure has occurred."

More Information

Iodine, at About.com

Thyroid Cancer

SOURCE: Journal of the National Cancer Institute 2005;97:703-705,724-732.