Iodine-rich Foods

Iodine in iodine-rich foods is a crucial nutrient that helps regulate thyroid function and metabolism. While iodine deficiency is rare in developed countries, ensuring you're getting enough of this essential mineral is still important. Luckily, plenty of delicious and easy-to-find foods are rich in iodine. Here are 5+ iodine-rich foods to consider adding to your diet.

Iodine in Food

Iodine was discovered by the French chemist Bernard Courtois in 1811 during saltpeter manufacture after adding sulfuric acid to the ash residue. A purple vapor came off, forming sublimated deposits of shiny purplish-black crystals on the sides of vats. The element is a halogen (a part of the fluorine, chlorine, and bromine series). It does not form a liquid but vaporizes on heating and crystallizes into a solid from the gas phase on cooling.

The Iodine Mineral

As the ion, I^–, it carries a negative electric charge and readily combines with potassium anions (K⁺) to form stable potassium iodide salt, KI. Consequently, it occurs sparingly in the form of iodides in seawater and is extracted from seaweeds, Chilean saltpeter, and nitrate-bearing caliche in brines from ancient sea deposits. Iodine is also present in brackish waters from oil and salt wells.

Iodine-rich Foods in the Diet

Iodine is an essential trace mineral with just one known function in the body: its role in the production of the hormone thyroxine (T4) and triiodothyronine (T3). Both hormones control the metabolic rate and the conversion of food and fat into energy. In addition, the level of body heat produced is also controlled by this important mineral.

Sources of Iodine

Good sources of iodine are:

Health Benefits of Iodine

Iodine plays a part in preventing lethargy, tiredness, and excessive weight gain. Unfortunately, sub-optimal iodine intake (T4 deficiency) leads to these symptoms, and lack of iodine is common globally. The chief symptoms of iodine deficiency are:

Iodine Deficiency

Iodine deficiency during pregnancy may lead to cretinism in the newborn (abnormal mental and physical development). With an underactive thyroid, a child’s brain can’t develop properly, which leads to mental retardation. This is seen in parts of Europe, Brazil, New Zealand, and the Himalayas. In some parts of the world, 90 percent of the population is iodine deficient.

Example

For example, in Indonesia, it’s estimated that there are 1.5 million mentally disabled children and 0.8 million with cretinism. Yet these conditions are easily preventable with expectant mothers being given injections of iodized oil before the sixth month of pregnancy. Later injection will be ineffective. In developed countries, newborns are screened for cretinism as part of the heel-prick test done shortly after delivery.

Goiter

Excessive iodine deficiency leads to thyroid gland swelling called goiter. Victims are those who restrict salt intake and who never eat iodine-rich seafood. Sub-optimal iodine consumption can be remedied with iodine supplements to boost metabolism.

Selenium and Iodine

The mineral selenium also plays a role in the metabolism of thyroid hormones, and the effects of iodine deficiency are worsened by low selenium levels in the body.

Iodine Dosage

The RNI and RDA for iodine are both around 150 mcg daily for adults. Athletes and those who sweat a lot need to watch out because 150 mcg of iodine can be lost through sweating. The upper safe level of iodine supplementation is 500 mcg or 0.5 mg daily.

Iodine Supplements

Supplementation is advisable if you can’t get hold of seaweed such as kelp or bladder wrack (Fucus species). However, 3 percent of people are allergic to iodine supplementation. As always, consult a doctor or pharmacist before taking any supplements over the long term.

Excessive Iodine Intake

Too much iodine intake may lead to a metallic taste in the mouth, headache, diarrhea, rashes, vomiting, and even goiter.

Iodine-Rich Foods

1. Seaweed

Seaweed is one of the best sources of iodine. It’s also a versatile ingredient that can be added to salads, soups, and sushi rolls. Kombu kelp, Wakame, and Nori are great seaweeds containing lots of iodine. Of these three iodine-rich foods, Kombu kelp contains more iodine than other seaweed.  Indeed, a sheet of Kombu (1 g) can contain up to 3 mg of iodine, which is 2000 times the RDI, so watch out and don’t overdo it. 

2. Cod and Haddock

Most people in Britain like a type of food called Fish’ n’ Chips from a chip shop, especially when holidaying at seaside resorts. Although the price of cod or haddock have gone up through the roof since 2020, these kinds of white fish are low in fat and have high iodine. For example, a 3 oz cod fillet has around half the iodine RDA.  However, the level of iodine in white fish varies slightly depending on whether the fish is wild-caught or comes from a fish farm.

3. Dairy Products

In the UK, milk is relatively high in iodine compared with other countries, at 200 mcg per pint, making it one of the most iodine-rich foods. So, a glass of milk (less than half a pint) contains 85 mcg of iodine or a third of the RDI. If you drink a pint of British milk each day, your iodine levels will be okay. In the United States, dairy products are significant sources of iodine.

Cattle Feed

But it depends on what’s in the cattle feed. A Boston study found that all milk had at least 88 mcg per 1 cup, so that’s okay. Some brands may contain nearly 170 mcg per cup. So, a cup of milk in the U. S. can provide 60–110 percent of the RDA of iodine.  Yogurt and cheeses are, products derived from milk, therefore, are also good sources of iodine.

4. Pink Himalayan and Iodized Salt

Pink Himalayan salt is not really one of the iodine-rich foods, but iodized salt is. Table salt can be marked iodized. All that means is that the refined salt has had a small amount of iodine added, which helps combat iodine deficiency. Pink Himalayan salt is unrefined with no added iodine. It contains only a trace amount of natural iodine but nowhere near as much as iodized table salt. However, it has many trace minerals.  A quarter teaspoon of iodized table salt has around 70 mcg of iodine or nearly half the RDI.

5. Other Iodine-Rich Foods

Eggs, shrimps, dried plums, and tuna are also good sources of iodine. The iodine in eggs is in the yolk and comes from the iodine added to chicken feed. Shrimp and tuna are seafood and get their iodine from the sea. Remarkably, dried plums are also one of the iodine-rich foods.

See also: Chloride; Chromium; Cobalt; Copper; Iodine; Iron; Magnesium; Molybdenum

Synonymous terms: iodine rich foods; vegetarian iodine rich foods list; how much iodine per day for thyroid; iodine food

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