The Low-Iodine Diet for Radioactive Iodine Treatment

A low-iodine diet limits the intake of iodine from food to less than 50 micrograms (mcg) per day in preparation for radioactive iodine treatment. If you have too much iodine in your body, your thyroid gland might take from those reserves rather than the radioactive iodine used to treat hyperthyroidism and certain types of thyroid cancer.

Following a low-iodine diet two weeks before starting radioactive iodine treatment increases the odds of an optimal response. You would also need to continue the diet one to two days after the completion of treatment.

This article lists the foods you can and cannot eat on a low-thyroid diet. It also explains the benefits of a low-iodine diet and healthier ways to obtain iodine from the foods you eat.

Foods Not Allowed on a Low-Iodine Diet

A low-iodine diet involves the restriction not only of foods that are high in iodine but also foods that affect the absorption of iodine.

Foods that you need to avoid on a low-iodine diet include:

• Iodized salt
• Dairy products, including milk, cheese, cream, yogurt, butter, and ice cream
• Whole eggs, egg yolks, and any foods containing whole eggs
• Seafood, including all fish and shellfish
• Seaweed and kelp
  
• Bread products made with dough conditioners like sodium iodate that prolong shelf life
• Soy products, including soy sauce, soy milk, and tofu
  
• Blackstrap (sulfured) molasses
• Cured meats or fish, including ham, bacon, lox, and corned beef
• Red-colored food made with FD&C red dye #3
• Foods containing additives like carrageenan, agar-agar, alginates, or nori
  

Iodine in Medications and Supplements

In addition to the iodine found in food, you'll need to check for any iodine-containing substances in the medications or supplements you take.

Among the considerations:

• Some medications and supplements contain an iodine-containing colorant FD&C red dye #3, also known as erythrosine.
• There are also supplements that contain iodine in different forms, including those made with kelp or dulse.
• Iodine is found in many herbal supplements. Because these products are not strictly regulated, there may not be any mention of iodine on the product label.

You'll need to avoid these products prior to and during radioactive iodine treatment.

Before starting treatment, ask your healthcare provider if any of the medications or supplements you take contain iodine. If so, your provider may be able to recommend a substitute, If not, they can tell you whether it is OK to temporarily stop the drug.

Do not stop taking any chronic medications without first speaking with your healthcare provider.

What to Eat on a Low Iodine Diet

There are many foods you can eat on a low-iodine diet that ensure balanced nutrition. This includes the recommended daily intake of salt (sodium). It is important to remember that the aim of a low-iodine diet is not to avoid salt but to avoid iodized salt.

Foods you can eat while on a low-iodine diet include:

• Non-iodized salt
• Fresh fruit and vegetables
• Frozen vegetables
• Canned fruit
• Unprocessed meats, including beef, pork, and poultry
• Non-dairy milk and dairy (but not soy milk)
• Pasta and rice
• Bread made without iodized salt or dairy
• Matzo crackers
• Egg whites
  
• Unsalted nuts and nut butter
• Unbuttered popcorn with non-iodized salt or no salt
• Vegetable oils 
• Coffee and tea without cow's or soy milk
• Soft drinks, coffee, tea, and fruit juices
• Sugar, jam, jelly, honey, and maple syrup

Can I Have Prepared Foods?

If ordering take-out or eating in a restaurant, be sure to exercise some caution. While some ingredients in a dish may be quite obvious, others—like those in a "special sauce"—may not be. You may be able to request that your food is made without salt or with non-iodized salt.

With that said, you may want to play it safe and simply avoid take-out and prepared foods prior to and during radioactive iodine treatment.

Keep in mind that baked goods are often made with iodized salt, salted butter, egg yolks, and dairy. Seek out specialty grocery stores and bakeries that sell items prepared with low iodine. Making these yourself at home may be even safer.

Benefits of a Low-Iodine Diet

Iodine is the mineral your body uses to make important thyroid hormones. The importance was recognized back in 1924 when iodized salt first became commercially available in the United States to help overcome high rates of iodine deficiency.

But today, iodine deficiency is uncommon due to the widespread use of iodized salt in food preparation and production. Most people can get the recommended daily intake of iodine—ranging from 150 mcg for teens and adults to 220 mcg for pregnant people—from the foods they eat even if table salt is not added.

While a low-iodine diet is an essential part of radioactive iodine treatment, it is not recommended on an ongoing basis as it deprives you of an essential mineral that you can only get from food or supplements. Consuming less than 50 mcg per day on a continual basis severely depletes the iodine stores in your body and can lead to hypothyroidism (low thyroid function).

With that said, some of the principles of a low-iodine diet can be beneficial. This is because many people in the United States get iodine from processed foods that are high in iodized salt. These foods (including fast foods, baked goods, and processed meats) tend to have excessive amounts of sodium that contribute to high blood pressure and heart disease.

Processed foods also tend to be high in saturated fat, sugar, and refined carbs, increasing the risk of obesity, type 2 diabetes, and coronary artery disease.

By cutting back on processed foods, you can significantly reduce your risk of these diseases. You can instead get your recommended daily intake of iodine from "real" foods such as fish, seafood, dairy, and eggs—and the judicious use of iodized salt.

Summary

Before beginning radioactive iodine treatment, you will need to follow a low-iodine diet. While there are some foods that you will need to avoid, there are many food and drink options that adhere to a low-iodine diet. Keep in mind certain medications may also contain iodine and may need to be switched before you begin your treatment.