Understanding a Low-Iodine Diet

Radioactive iodine (RAI) therapy is a treatment used for thyroid cancer. If you're going to get RAI, your healthcare provider may tell you to be on a low-iodine diet for up to 2 weeks before treatment. This helps the RAI treatment work better.

What is a low-iodine diet?

A low-iodine diet means you need to limit the amount of iodine you consume. You'll need to stay away from foods high in iodine and eat more foods low in it.

Iodine is a chemical found naturally in some foods. It's also added to some foods. Your body needs iodine. It helps your thyroid work the way it should. Your thyroid makes hormones that help control your body’s breathing, temperature, and metabolism.

Why might you need to follow a low-iodine diet?

You may need be on this diet if you've had surgery to remove your thyroid because of thyroid cancer, and you're now going to get RAI treatment. RAI treatment helps kill any leftover cancer cells in your body. It may also kill normal thyroid cells.

During RAI treatment, you swallow a pill that has the RAI in it. Any normal thyroid cells and any thyroid cancer cells in your body will absorb the RAI. The radiation will then kill these cells. Being on a low-iodine diet before treatment will help your body better take in the RAI.

How do you follow a low-iodine diet?

When you're on a low-iodine diet, you need to stay away from foods high in iodine. Reading food labels can help you make the right food choices.

Here are some general tips:

Don’t eat these high-iodine foods:

• Iodized salt or other seasonings and foods that have it in them

• Milk and other dairy products such as cheese, butter, ice cream, yogurt, and milk chocolate products

• Fish, sushi, and other seafood

• Cured meats

• Kelp and other types of seaweed

• Egg yolks and foods with whole eggs in them

• Vitamins and herbal supplements that contain iodine

• Protein shakes and nutrition drinks

• Foods with red dye #3 in them, such as maraschino cherries

• Foods with the additives carrageen, agar-agar, alginate, or nori

While on this diet, you can still eat many other foods, such as:

• Non-iodized salt or sea salt and foods made with it

• Egg whites

• Fresh fruits and vegetables

• Grains, cereals, and pasta made without high-iodine ingredients

• Baked goods not made with iodine-containing ingredients, such as salt or butter

• Sugar, jelly, honey, and maple syrup

• Black pepper and fresh or dried herbs

• Unsalted nuts and nut butters

• Soda, fruit juices, beer, and wine

• Coffee and tea without creamer or milk

• Limited amounts of beef and poultry

Ask your healthcare team any questions you have about certain foods. Also talk with your healthcare provider about your medicines. Some may have iodine in them. But don't stop taking medicines unless your provider tells you to. Also ask your healthcare provider about soy products. These don’t have iodine in them. But they may weaken RAI treatment.

While on this diet, it’s also a good idea to not eat out at restaurants. It can be hard to know for sure if a restaurant uses non-iodized salt or other iodine-containing ingredients.