Iodine is a mineral necessary for the production of thyroid hormones.
Thyroid hormones — which are secreted by the thyroid — affect nearly every organ system in the body.
To increase the effectiveness of radioactive iodine therapy — a treatment for thyroid cancer — you may need to temporarily follow a low-iodine diet.
In other instances, if you consume excessive amounts of iodine, you may be able to improve thyroid function by reducing your intake.
This article explains what to eat and avoid on a low-iodine diet and provides a sample low-iodine diet sample menu.
Who may need to follow a low-iodine diet?
Iodine is an essential mineral and component of the thyroid hormones triiodothyronine (T3) and tetraiodothyronine or thyroxine (T4) (1).
The butterfly-shaped gland in your neck that sits just above your collarbone known as the thyroid secretes these hormones.
The thyroid hormones play an important role in regulating your energy levels, body temperature, body weight, and metabolism, among other things.
The body needs iodine to make thyroid hormones and support these functions.
Although essential for thyroid health, you may need to restrict iodine, such as 4–7 days before receiving radioactive iodine therapy for thyroid cancer (2).
In other instances, if you’re consuming too much iodine, decreasing your intake may improve your thyroid function.
Excess iodine causes the thyroid to become dysfunctional, which, depending on the individual, can lead to insufficient thyroid hormone production (hypothyroidism) or excess thyroid hormone production (hyperthyroidism).
Excess intake may also contribute to the development of Graves’ and Hashimoto’s disease, which are autoimmune disorders that occur when antibodies from the immune system attack and damage the thyroid (3).
Iodine is usually restricted to 50 mcg per day on a low-iodine diet but the level of restriction varies depending on the reason for which the diet was prescribed or recommended (2).
For reference, adults need 150 mcg of iodine per day, but during pregnancy and lactation, this need increases to 220 and 290 mcg per day, respectively (4).
SUMMARY: You may need to follow a low-iodine diet before radioactive iodine therapy or if your thyroid becomes dysfunctional due to excess iodine.
Low-iodine diet food list
Many foods and additives contain iodine.
However, it can be difficult to know which foods contain iodine and in what amounts since most products don’t include iodine on the nutrition facts label.
And even if it is listed, it may not be accurate since the iodine content of foods can vary significantly depending on the iodine content of soil and the agriculture or manufacturing practices that introduce iodine to foods (5).
Still, it’s good to have a general idea of which foods are usually lower in iodine and which ones are higher.
Low-iodine foods to eat
Many foods contain iodine, but they’re not good sources.
This allows you to eat a variety of foods while following a low-iodine diet.
Here’s a list of low-iodine foods that contain less than 10% of the daily value (DV) for iodine per standard serving (6):
- Fruits: apples, apricots, avocado, bananas, blueberries, grapefruit, grapes, oranges, peaches, pears, pineapple, strawberries, watermelon
- Vegetables: asparagus, beets, broccoli, brussels sprouts, cabbage, carrots, cauliflower, celery, collards, corn, cucumbers, green beans, onions, peas, potatoes, squash, tomatoes
- Legumes: beans (black, pinto, kidney, white), peanut butter, peanuts
- Nuts and seeds: almonds, sunflower seeds, walnuts
- Grains and cereals: oatmeal, pasta (boiled without iodized salt), quinoa, rice, cereals (bran, cornflakes, crisped rice, granola, shredded wheat, etc.), bagels, biscuits, bread, crackers, tortillas
- Dairy and eggs: butter, cheese (Monterey jack or parmesan), cream cheese, half and half, sour cream, egg whites
- Seafood: shrimp (precooked), catfish, halibut, pink salmon (canned), swai, tilapia, trout, tuna (canned in water), scallops
- Meats: lunch meats, sausage, salami, chicken turkey, ham pork, beef, lamb
- Mixed dishes: chicken potpie, coleslaw, macaroni salad, meatloaf, pasta mixes, potato salad, spaghetti with meat sauce, taquitos
- Snacks and sweets: candy, chips, granola bar, honey, popcorn, popsicles, pudding, syrups
- Fast food: fried chicken, chicken nuggets, french fries, hamburgers, tacos
- Condiments: margarine, mayonnaise, olive oil, salad dressing (coleslaw, creamy buttermilk, Italian, ranch), ketchup, mustard, barbeque sauce, soy sauce
- Soups, sauces, gravies, and condiments: broth (chicken), brown gravy, salsa, canned soups (broccoli cheese, chicken noodle, ramen, tomato, vegetable beef)
- Spices: sea salt (non-iodized)
- Beverages: almond milk, coconut water, energy drinks, sports drinks, soda, coffee, juices, tea, water
High-iodine foods to avoid
The major environmental source of iodine is the ocean.
As such, seafood is one of the best sources of iodine since marine plants and animals intake iodine from seawater.
Dairy products are another rich source of iodine, but not because iodine is a natural component of cow’s milk, but because it comes from iodine supplements in cattle feed and iodine-containing disinfectants used to sterilize milking equipment and the udders (7).
The other major source of dietary iodine is iodized salt.
Iodized salt was introduced in 1924 as an effective and inexpensive way to ensure adequate iodine intake for Americans (8).
Many other countries also use iodized salt for the same reason.
In America, only sodium chloride — commonly known as table salt — is iodized while the salt typically used in processed foods contains only minimal amounts.
However, about 70% of the salt that Americans consume is from packaged and processed foods like chips, hot dogs, frozen meals, and hot dogs, and fewer than 30% of consumers choose iodized salt for home cooking (8).
Still, dairy products and iodized salt are the primary sources of iodine for Americans.
Specialty salts, such as sea salt, kosher salt, Himalayan salt, and fleur de sel are not usually iodized and contain minimal amounts of iodine.
Other foods that contain high amounts of iodine are breads made with iodate, which manufacturers use to strengthen the dough.
You can identify bread that looking for the word “sodium iodate” in the ingredient list.
Here’s a list of low-iodine foods that contain 20% or more of the DV for iodine per standard serving (6):
- Vegetables: seaweed
- Grains: breads made with iodate dough conditioner, breadcrumbs
- Dairy and eggs: cheese (ricotta or swiss), cottage cheese, whole eggs, ice cream, cow’s milk, yogurt
- Seafood: crab, lobster, fish sticks, cod, haddock, pollock, clams, oysters
- Mixed dishes: corn dogs, macaroni and cheese, pizza, sushi (California roll)
- Soups: clam chowder
- Spices: iodized table or sea salt
- Beverages: some meal replacement drinks
In addition to these foods, some dietary supplements like multivitamins may contain iodine.
If you’re pregnant or planning to become pregnant, talk with your healthcare provider about taking a supplement containing iodine since it’s recommended during this time (9).
SUMMARY: Iodized salt and certain types of seafood tend to be the richest sources of iodine while others like fruits, vegetables, grains, and meats tend to be poor sources.
3-day sample low-iodine diet menu
Here’s a 3-day sample low-iodine diet menu:
- Breakfast: egg white omelet and oatmeal topped with blueberries
- Lunch: chickpea salad
- Snack: apple slices and almonds
- Dinner: baked tilapia, white rice, and sauteed green beans
- Breakfast: proats (protein oats) made with water
- Lunch: grilled chicken salad
- Snack: trail mix
- Dinner: vegetable beef soup and iodate-free baguette
- Breakfast: black bean breakfast bowl
- Lunch: hamburger and pasta salad
- Snack: hummus with veggies for dipping
- Dinner: pork roast and sauteed carrots
SUMMARY: Use this sample low-iodine diet menu to guide your menu planning and food choices.
The bottom line
Although iodine is essential for thyroid health, you may need to follow a low-iodine diet in preparation for radioactive iodine therapy or if you experience thyroid dysregulation due to excessive iodine intake.
A low-iodine diet generally restricts iodine to 50 mcg per day but the level of restriction may vary depending on the reason for which a low-iodine diet was prescribed or recommended.
Many foods contain iodine but they aren’t good sources allowing you to have a varied diet while limiting your iodine intake.
The primary sources of iodine include most types of seafood — including seaweed — dairy products, and breads made using iodate sodium.