Reducing salt intake won't make you iodine deficient, from the Harvard Heart Letter
The surplus of sodium in the American diet contributes to a host of cardiovascular problems, from high blood pressure and stroke to heart attack, heart failure, and more. Cutting back on salt is generally good for the heart and arteries. But some people fear that by doing this they won't get enough iodine in their diets. Not to worry, explains the June 2011 issue of the Harvard Heart Letter. Salt provides only a fraction of daily iodine intake for most Americans.
The human body needs iodine to make thyroid hormone. This hormone is critically important during fetal development, infancy, and childhood, for the brain and nervous system to develop normally. Later in life, thyroid hormone controls metabolism. Adults who don't take in enough iodine can develop a goiter (a swelling of the butterfly-shaped thyroid gland in the neck), and the low output of thyroid hormone can lead to sluggish metabolism, poor thinking skills, infertility, thyroid cancer, and other conditions. Since the 1920s, iodized salt has been one way of preventing iodine deficiency.