Before getting the radioactive iodine
treatment, patients are supposed to follow a low iodine
diet for a week or two beforehand, so the thyroid is starved for iodine. That way, when they ingest the pill, it will travel to any thyroid tissue in the body. When on the low iodine diet, you're not supposed to have dairy products at all due to iodine in cattle feed, the products containing iodine used to clean teats and udders, and a small amount from equipment cleaning products. Interesting.