What food is highest in iodine? A complete nutrition diet guide

October 24, 2025 •

5 min read

Approximately one-third of the global population has insufficient iodine intake. When it comes to answering the question of what food is highest in iodine?, the answer is resoundingly kelp and other seaweeds, but many other sources are also vital for a balanced nutrition diet.

Quick Summary

This article explores the top dietary sources of iodine, including marine vegetables like kelp, seafood, dairy, and fortified products. It details their importance for thyroid health and proper intake, comparing iodine content across different food groups and providing guidance on safe consumption.

Key Points

Kelp is the Highest Source: Dried kelp is the most iodine-dense food, though its concentration can vary and requires careful, moderate consumption to avoid excess.
Seafood and Dairy are Rich: Excellent sources include fish like cod, shellfish such as oysters and shrimp, as well as milk and yogurt.
Iodized Salt is a Public Health Staple: Fortified table salt remains an accessible and widespread method of preventing iodine deficiency, although the use of non-iodized salt in processed foods has become more common.
Balance is Essential: Too much iodine can be as problematic as too little, with the potential to cause thyroid dysfunction in sensitive individuals.
Special Diets Require Planning: Vegans and those on low-sodium diets must carefully plan their intake using fortified products, plant sources like prunes and potatoes, or supplements under medical supervision.
Cooking Matters: The method of cooking can impact iodine levels. Boiling can cause loss, whereas baking and frying generally preserve more of the mineral in fish.
Soil Affects Plant Levels: The iodine content in vegetables and fruits is highly dependent on the mineral composition of the soil they are grown in.

The Unrivaled King of Iodine: Seaweed

For anyone seeking the single most concentrated source of dietary iodine, seaweed is the clear winner. The iodine in seaweed comes from its ability to concentrate the mineral up to 30,000 times the level found in seawater. However, the exact content can vary dramatically depending on the species and growing environment. Brown seaweeds tend to be the highest, and some species of kelp (like kombu) contain massive amounts that can easily exceed the recommended daily allowance in tiny portions. Nori, the red seaweed used in sushi, and wakame, commonly found in miso soup, also offer significant amounts, but generally less than the potent brown varieties.

Because the iodine levels in seaweed can be so high, it is crucial to consume it in moderation to avoid excessive intake, which can cause thyroid dysfunction in some people. Dried kelp flakes are an easy way to add a mineral boost to soups, salads, and dressings while carefully controlling the quantity.

Other Top Marine and Animal-Based Sources

While seaweed takes the top spot, several other foods offer excellent and more predictable iodine levels. These sources are a cornerstone of healthy iodine intake for many populations.

Fish and Shellfish: Since the world's iodine is concentrated in the oceans, it's no surprise that marine life is a rich source.
- Cod: A lean, white fish that is a particularly high source of iodine, with one 3-ounce serving providing a significant portion of the daily value. Its exact content can vary based on geography.
- Oysters: These mollusks pack a powerful iodine punch, with a 3-ounce serving providing nearly two-thirds of the daily requirement.
- Shrimp: A low-calorie option that offers a good contribution to iodine intake.
Dairy Products: Milk and dairy are major sources of iodine in many industrialized countries, though the content can vary based on the cow's diet and farm practices.
- Yogurt: Especially Greek yogurt, offers a higher concentration of iodine per serving than regular milk.
- Milk: A single cup of milk can provide a substantial amount of iodine.
Eggs: The yolk of an egg is a good source of iodine and other essential nutrients. One hard-boiled egg can contribute over 20% of the daily value.

Fortified Foods and Iodized Salt

Beyond natural sources, many countries have implemented public health programs to combat widespread iodine deficiency by fortifying common foods. Iodized table salt is the most prominent example.

Iodized Table Salt: This remains a critical and accessible source of iodine for many people. However, as public health campaigns encourage lower sodium intake, and with the rise of non-iodized salts (like sea salt or kosher salt) and the use of non-iodized salt in processed foods, this source is becoming less reliable.
Fortified Bread: In some regions, bread and other grains are fortified with iodate dough conditioners, adding a significant amount of iodine. However, this varies by country and brand, and the iodine content isn't always listed on nutritional labels.

Comparison of Iodine-Rich Foods


Food (Serving Size)	Approx. Iodine Content	Notes
Dried Kombu Kelp (1g)	Up to 2,984 mcg	Highly variable; caution needed to avoid excess.
Dried Nori Seaweed (5g)	~116 mcg	Commonly used for sushi rolls.
Cod, Baked (3 oz)	~146 mcg	Lean white fish with high iodine content.
Greek Yogurt, Plain (¾ cup)	~87 mcg	Excellent dairy source, also rich in protein.
Milk, Nonfat (1 cup)	~84 mcg	A reliable daily source for many.
Iodized Table Salt (¼ tsp)	~78 mcg	A key source, but moderation on salt intake is important.
Hard-Boiled Egg (1 large)	~31 mcg	The iodine is concentrated primarily in the yolk.
Shrimp, Cooked (3 oz)	~13 mcg	A low-calorie protein option.
Prunes (5 prunes)	~13 mcg	A modest vegan source.

Iodine for Special Diets: Vegans and Low-Sodium Dieters

For individuals following vegan diets, or those on low-sodium plans who avoid iodized salt, meeting the daily iodine requirement of 150 mcg can be challenging. Seafood and dairy, the most common rich sources, are absent from these diets.

Vegan Food Sources: While some plant-based foods contain small amounts of iodine, it is often dependent on the soil's mineral content, which varies greatly. Some options include prunes, lima beans, and potatoes, but their iodine levels are much lower than marine sources.
Supplementation: For those on restricted diets, a daily multivitamin or an iodine-specific supplement containing potassium iodide can be a reliable way to ensure adequate intake. Always consult a healthcare provider to determine the right dosage.

The Risks of Imbalance: Deficiency and Excess

Maintaining the right balance of iodine is crucial for thyroid health. Both deficiency and excess can cause problems.

Iodine Deficiency

When iodine intake is too low, the body cannot produce enough thyroid hormones. This can lead to a range of issues, including:

Goiter: The thyroid gland may enlarge in an attempt to capture more iodine.
Hypothyroidism: The metabolism slows down, causing fatigue, weight gain, and cold intolerance.
Developmental Issues: During pregnancy and infancy, severe iodine deficiency can lead to irreversible intellectual disabilities.

Iodine Excess

While rarer, excessive iodine intake can also lead to thyroid dysfunction. This is a particular risk for people consuming large amounts of kelp or taking unregulated supplements. Symptoms can include elevated TSH levels, hyperthyroidism, or even thyroiditis. The Tolerable Upper Intake Level (UL) for adults is 1,100 mcg per day.

Conclusion: A Balanced Approach to Iodine

Ultimately, a healthy nutrition diet for iodine intake is about balance and variety. While kelp is definitively the food highest in iodine, relying solely on it is ill-advised due to the risk of excess. Incorporating a mix of reliable sources like fish, dairy, and eggs, alongside using iodized salt in moderation, is the safest and most effective strategy for most people.

For those on restricted diets, careful planning and the potential use of supplements under medical guidance are necessary. Regularly checking with a healthcare provider can help ensure optimal iodine levels, especially for vulnerable groups like pregnant women who have increased needs. A balanced diet provides not only the necessary iodine for thyroid function but a wide range of nutrients essential for overall well-being. For more information, the National Institutes of Health provides comprehensive details on iodine and health.

Frequently Asked Questions

Dried kelp, a type of brown seaweed, has the highest concentration of iodine found in any food. However, the amount can be extremely high and variable, so it should be consumed in moderation.

Other excellent sources of iodine include marine foods like cod, shellfish (oysters, shrimp), dairy products such as milk and yogurt, and eggs.

Yes, milk and other dairy products are a major source of iodine in many diets. However, the exact content can vary depending on factors like farming practices, feed, and geographic location.

Vegans need to be proactive about their iodine intake since they avoid primary sources like seafood and dairy. They can rely on iodized salt, iodine supplements, or include certain plant-based foods like potatoes and lima beans, though the amount in plants is often lower and less consistent.

Yes, excessive iodine intake is possible and can be harmful. It can lead to thyroid dysfunction, including both hypothyroidism and hyperthyroidism, especially in susceptible individuals. Sources like kelp and high-dose supplements carry this risk.

Cooking methods can affect iodine content. Studies on cod show that boiling can lead to a significant loss of iodine into the water. However, cooking methods like pan-frying and baking tend to preserve more of the mineral.

Iodized table salt is the most reliable salt source for iodine. Specialty salts like sea salt and Himalayan salt are not typically iodized and contain negligible amounts of iodine.

Iodine deficiency can cause an enlarged thyroid gland (goiter) and hypothyroidism, leading to symptoms like fatigue, weight gain, and cold intolerance. In pregnant women, severe deficiency can cause serious developmental issues for the fetus.