Iodine and Your Thyroid: What You Need to Know

Health Professional, Medical Reviewer

What is iodine and why is it important?

Iodine is an essential element in our diet needed to produce thyroid hormone since our bodies are unable to make it. About 100 years ago, iodine deficiency was very common in the United States and led to goiter (enlargement of the thyroid gland). Since the decision to iodize table salt in the 1920s, goiter has been virtually eliminated in the United States, though in many underdeveloped countries this condition is still a serious health risk. In addition to goiter, iodine deficiency can lead to hypothyroidism and complications during pregnancy, including developmental problems for the fetus. While it is less common in the United States, the American Thyroid Association estimates that 40 percent of the world’s population is still at risk for iodine deficiency.

How much iodine do I need?

The Institute of Medicine of the Natural Academies has established a recommended daily allowance (RDA) of 150 micrograms (mcg) per day for all adult men and women. During pregnancy and lactation, the RDA increases to 220 mcg and 290 mcg, respectively. By consuming iodized table salt (which is found in virtually all canned and processed foods), and eating a balanced diet, it is relatively easy to achieve this RDA.

What foods are good sources of iodine?

Foods highest in iodine include seaweed (such as kelp), dairy products (milk, cheese, yogurt, ice cream, and frozen yogurt), eggs, soy products (soy sauce and soy milk), and seafood (shellfish and cod). Foods containing iodized salt (such as breads and cereals) also can be good sources of iodine.

Who needs to limit their iodine intake?

If you have been diagnosed with thyroid cancer and are preparing for radioactive iodine therapy, you have most likely been told to follow a low iodine diet prior to treatment to help maximize the effectiveness of the radiation. Since iodized salt is added to many prepared and packaged foods, iodine is found in varying amounts in countless foods and beverages. In addition to avoiding foods containing iodized salt, it is important to avoid dairy products, fish, shellfish, grains, cereals, breads, soy products, beef, and poultry if you are following a low-iodine diet.

In addition to many foods and beverages, iodine is found in other things we consume on a regular basis. When following a low iodine diet, avoid vitamins, minerals, and herbal supplements that contain iodine. Also stay away from foods that contain the additives agar-agar, alginate, nori, carrageen, or FD&C red dye #3 due to their iodine content. Some medications, particularly if they are red in color  (such as cough medicine), should be avoided on a low iodine diet, so talk with your physician about your medication regimen prior to starting treatment.

The bottom line

While iodine is an essential element in the human diet, excessive consumption by someone undergoing radiation treatment for thyroid cancer can pose a serious health risk. If you have questions about your diet or how nutrition can help you manage a chronic condition, talk with your health care provider or a registered dietitian.

See more helpful articles:

Understanding the Dangers and Benefits of Iodine

About Thyroid Cancer — Risks, Statistics, Different Types

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