Lindsey M. VanDyke, DO, FACOI, FEAA. Board certified in Internal Medicine and Endocrinology. Mansfield, Texas.
The short answer
A low iodine diet empties your body’s iodine stores so radioactive iodine treatment works better. You avoid iodized salt, dairy, seafood, egg yolks, soy, commercially baked goods and anything containing red dye number 3. You can eat fresh meat, fresh fruit and vegetables, plain grains, unsalted nuts and non iodized salt. It is temporary, and your own doctor will tell you exactly how long to follow it.
Who needs a low iodine diet?
People preparing for radioactive iodine therapy or a radioactive iodine scan, usually after thyroid cancer surgery.
The reasoning is simple. Radioactive iodine works because thyroid tissue absorbs iodine. If your body is already full of iodine from food, there is less room for the treatment to be taken up, and it works less well. Emptying the tank first makes it more effective.
This is not a diet for weight, general thyroid health, or hypothyroidism. It is short term preparation for a specific procedure.
How long do you follow it?
Commonly one to two weeks before treatment, and sometimes briefly afterwards.
Follow the duration your own doctor gives you, because it varies with the treatment plan. If nobody has given you a number, ring and ask rather than guessing. Stopping early is the most common way people undermine the preparation.
Why iodine turns up in so many foods
Iodine is used in the care and feeding of animals, and as a stabiliser and safety element in food processing. It therefore appears in varying amounts across almost all food and drink, including things that seem harmless.
That is why the list matters more than instinct. Most people would never guess that bread or a maraschino cherry is a problem.
Foods to avoid
| Avoid | Why |
|---|---|
| Iodized salt | The single largest source. Non iodized salt is fine. |
| All dairy: milk, cheese, butter, yoghurt, cream, ice cream | Consistently high in iodine. |
| Seafood, fish, shellfish, seaweed, kelp | The highest iodine foods there are. |
| Egg yolks and whole eggs | Egg whites and egg substitutes are permitted. |
| Soy: soy sauce, tofu, soy milk, soybeans | High in iodine. |
| Commercially prepared bread and bakery items | Often contain iodate dough conditioners. |
| FD&C red dye number 3 | In maraschino cherries and sometimes as pink or red colouring in drinks and sweets. |
| Restaurant food | You cannot verify the salt or ingredients used. |
Foods you can eat
- Fresh meat. Beef, lamb, veal, pork and turkey, around six ounce portions.
- Fresh fruit and dried fruit.
- Fresh or frozen vegetables without added salt.
- Plain grains. Rice, oats, matzo crackers, home baked bread made without iodized salt or dairy.
- Unsalted nuts and unsalted nut butters.
- Egg whites and egg substitutes.
- Non iodized salt, oil and vinegar.
- Black coffee and tea.
A day of meals
Breakfast. Fresh fruit, oatmeal with permitted toppings, egg substitute, permitted toast, black coffee or tea.
Lunch. Vegetarian or chicken and rice soup, matzo crackers, rice with vegetables, salad dressed with oil and vinegar, fruit.
Dinner. Six ounces of roast beef, lamb, veal, pork or turkey, with potatoes, vegetables and salad.
Snacks. Fresh fruit, dried fruit, raw vegetables, unsalted nuts, unsalted peanut butter.
Mistakes people commonly make
- Assuming sea salt is safe. Check the label. Non iodized is what matters, not whether it is sea salt.
- Eating out. You cannot confirm what a kitchen used.
- Forgetting drinks and sweets. Red dye number 3 hides in pink and red products.
- Treating it as low salt. It is not. You can salt your food, with non iodized salt.
- Stopping early. Follow it to the day you were given.
- Stopping medication without asking. Speak to your doctor first, particularly about red coloured tablets or anything containing iodine.
Medications and supplements
Do not stop any prescribed medication without speaking to your doctor first.
Some tablets contain iodine, and some red coloured medications contain the same dye you are avoiding in food. Multivitamins and kelp or seaweed supplements are usually stopped, but that is your doctor’s decision, not something to work out from a website.
Questions about your own treatment
Every treatment plan is slightly different, and the duration and details should come from the doctor managing your care.
Dr. VanDyke is a board certified endocrinologist in Mansfield, Texas, seeing patients from across Dallas Fort Worth. New patients are seen within two weeks. Telehealth is available in seven states.
Call or text (817) 380-4880.
This page is educational and is not medical advice. Follow the instructions given by the doctor managing your treatment.
Frequently asked questions
1. What foods are low in iodine?
Fresh meat, fresh fruit and vegetables, plain grains such as rice and oats, unsalted nuts, egg whites, and non iodized salt.
2. How long do you follow a low iodine diet?
Commonly one to two weeks before radioactive iodine treatment, sometimes continuing briefly afterwards. Follow the duration your own doctor gives you.
3. Can you eat bread on a low iodine diet?
Not commercially prepared bread, which often contains iodate dough conditioners. Home baked bread made without iodized salt or dairy is usually fine.
4. Is sea salt allowed on a low iodine diet?
Only if it is non iodized. Check the label, because some sea salt is iodized.
5. Can you eat eggs?
Egg whites and egg substitutes are permitted. Avoid yolks and whole eggs.
6. Why do I need this before radioactive iodine?
Radioactive iodine works because thyroid tissue absorbs iodine. Emptying your stores first means more of the treatment is taken up, which makes it more effective.
7. Is a low iodine diet the same as a low salt diet?
No. You can salt your food, as long as the salt is not iodized.
8. Can I eat at restaurants?
Better not to. You cannot verify what salt or ingredients were used, and it is only a short period.
9. Can I drink coffee and tea?
Yes, black. Avoid milk and cream, and check that nothing red or pink has been added.
10. Should I stop my vitamins?
Ask your doctor. Multivitamins and kelp or seaweed supplements are usually stopped, but do not stop prescribed medication on your own.
11. What happens if I slip up?
Do not panic and do not abandon the diet. Tell the team looking after your treatment, because they can advise whether anything needs adjusting.
12. Will this help my thyroid generally?
No. It is preparation for a specific procedure, not a treatment for hypothyroidism or general thyroid health.
13. Can I be seen by video?
Yes, telehealth is available in seven states, which is often easier during treatment preparation.
14. How soon can I be seen?
New patients are seen within two weeks. Across Dallas Fort Worth, two months is the more common answer.
15. How does payment work?
If you have Medicare, the practice contracts directly with Medicare and bills them after your care. If you have private insurance, the practice contracts with you directly and gives you the paperwork to claim reimbursement from your insurer.