Iodine is trace element that allows the thyroid gland to synthesize hormones. Normally, the Food and Nutrition Board recommends that adults consume 150 micrograms per day. A low iodine diet is recommended prior to a radioactive immunoassay, or RAI, which is a diagnostic test used to detect or monitor diseases of the thyroid gland.
Purpose
Following a low iodine diet allows your body to deplete iodine stores. During the radioactive immunoassay, radioactive iodine is administered. Because iodine stores are depleted, the thyroid gland pulls in the radioactive iodine, saturating the thyroid cells. When the thyroid gland contains mostly radioactive iodine, the radioactive immunoassay reading is clear and more accurate.
Diet Basics
According to the Thyroid Cancer Survivors' Association, Inc., a low iodine diet typically begins 14 days prior to the radioactive immunoassay and continues for 1 to 2 days after treatment. The diet restricts iodine intake to less than 50 micrograms per day. While following the diet, you may eat as many low iodine foods, defined as foods having no more than 5 micrograms of iodine per serving, as you want. Limit medium iodine foods, which contain 5 to 20 micrograms of iodine, and avoid high iodine foods, which contain more than 20 micrograms of iodine.
Foods to Avoid
Iodized salt is one of the richest sources of iodine in the diet, containing approximately 400 micrograms per teaspoon. Avoid iodized salt as well as sea salt. Non-iodized salt is permitted. Because foods obtained from the ocean are usually high in iodine, avoid seaweed, kelp, fish and shellfish. Some foods contain ocean-based additives such as carrageenan, algin, alginate, nori and agar-agar. Read labels carefully and avoid any foods with ocean-based additives. Additionally, avoid dairy products, like cheese, milk, yogurt, ice cream, butter, cream and egg yolks, as well as commercially baked items, chocolate, soy products, potato skins, rhubarb, navy beans, pinto beans and kidney beans. Red dye #3 also contains iodine, so you must check labels for this food additive as well.
Foods to Limit
You may consume up to 5 oz. of fresh meats, like beef, pork, chicken, veal and lamb, per day. The Thyroid Cancer Survivors' Association, Inc. notes that whole meats generally contain less iodine than ground meats. You may also consume up to 4 servings of grains, such as cereal, pasta and bread, per day. It is important to check ingredient labels of these grains, however, and make sure that they are not made with ingredients that contain iodine.
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