What Plants Are High in Iodine? A Guide to Plant-Based Sources

December 13, 2025 •

4 min read

According to the National Institutes of Health, seaweeds like kelp, nori, and wakame are among the best food sources of iodine, a mineral critical for thyroid health. While iodine is more famously associated with seafood and dairy, many plants can also be part of a balanced intake, with sea vegetables offering the most concentrated amounts.

Quick Summary

Sea vegetables like kelp and nori are the most concentrated plant-based sources of iodine, but their content varies widely. Some terrestrial plants also contain this vital mineral.

Key Points

Sea Vegetables Are Richest: Seaweeds like kelp, nori, and wakame offer the most concentrated plant-based sources of iodine.
Use Kelp with Caution: Due to extremely high and variable iodine content, kelp (kombu) should be used sparingly, especially by those with thyroid conditions.
Reliable Sources on Land Are Rare: The iodine in terrestrial plants depends on soil quality, making them unreliable for consistent iodine intake.
Fortified Foods Provide Consistency: Checking labels for iodine fortification on plant-based milks offers a dependable way to ensure adequate intake.
Iodized Salt is a Key Strategy: Using iodized salt instead of non-iodized varieties like sea salt is a simple and effective method for preventing deficiency.
Goitrogens Are Not a Major Concern: While some plants contain goitrogens, they typically only pose a risk for those with very low iodine intake.

Sea Vegetables: The Richest Plant Sources of Iodine

Seaweed, or sea vegetables, are undoubtedly the most potent plant-based sources of iodine, absorbing the mineral directly from the ocean's waters. The concentration varies significantly by species and harvest location, so it's important to understand the different types and their potency.

Types of High-Iodine Seaweed

Kelp (Kombu): This brown seaweed is known for having extremely high and highly variable iodine levels, sometimes containing several times the daily recommended intake in a single serving. Because of this variability and potency, it should be used cautiously, especially by individuals with thyroid issues or those who are pregnant. Kelp is often found dried, in flakes, or as a supplement, but supplements should be avoided due to unpredictable iodine levels.
Nori: The dried seaweed used for sushi wraps, nori offers a more moderate and consistent amount of iodine than kelp, making it a safer and more reliable option for regular consumption. A couple of nori sheets can provide a significant portion of the daily requirement.
Wakame: A popular ingredient in miso soup and seaweed salads, wakame is another good source of iodine. Its content is generally lower than kelp but higher than nori, offering a balanced middle-ground for iodine intake.
Dulse: A red seaweed sold in flakes or dried fronds, dulse contains a moderate amount of iodine, typically more than nori but less than kelp. It is valued for its savory, slightly smoky flavor.

How to Safely Incorporate Seaweed

For most people, sprinkling a small amount of powdered or crumbled seaweed, such as dulse flakes or nori, onto meals a few times a week is an effective way to boost iodine intake without risking excess. It can be added to soups, salads, and pasta dishes. Always check the packaging for specific iodine content if possible, as it varies widely.

Land-Based Plants: A Less Reliable Source

The iodine content of terrestrial plants is heavily dependent on the iodine concentration of the soil they were grown in. Areas close to the coast or with soil rich in the mineral will produce plants with higher levels, while those from inland, mountainous regions typically have very little. For this reason, land plants are generally not a consistent or substantial source of iodine compared to sea vegetables.

Examples of Land Plants with Some Iodine

Potatoes (organic with skin): When grown in iodine-rich soil, organic potatoes can contain some iodine, with most of it concentrated in the skin.
Cranberries: These berries are known to contain a measurable amount of iodine, though it varies.
Strawberries: Similar to cranberries, strawberries can offer a small contribution to your daily iodine intake.
Green Beans & Lima Beans: These legumes contain small amounts of iodine.
Corn: Both organic and conventionally grown corn can contribute a small amount.

Fortified Foods and Iodized Salt

For those on a plant-based diet, relying solely on terrestrial plants for iodine is often inadequate. Fortified foods and iodized salt can be crucial for meeting nutritional needs.

Fortified Plant-Based Milks: Not all plant-based milk alternatives are fortified with iodine, but checking the nutrition label can help identify those that are. Fortified options can provide a consistent and reliable source similar to cow's milk.
Iodized Salt: The most common source of iodine for many is iodized table salt. Unlike regular or sea salt, which have negligible iodine content, iodized salt is fortified to help prevent deficiency.

Comparison of Iodine Sources


Source Type	Examples	Iodine Content	Reliability	Considerations
Sea Vegetables	Kelp, Nori, Wakame, Dulse	Very High to Moderate	Variable	Potential for excess (kelp), great for flavor and nutrition
Land Plants	Potatoes, Cranberries, Green Beans	Low to Very Low	Inconsistent (depends on soil)	Should not be relied upon as a primary source
Fortified Foods	Iodized plant milks, iodized salt	Consistent, Targeted	High	Check labels for fortification; mindful of salt intake

Understanding Goitrogens

It's worth noting that some nutritious plant foods contain naturally occurring substances called goitrogens, which can interfere with the thyroid's use of iodine. These include cruciferous vegetables (broccoli, cauliflower, cabbage) and soy. However, this effect is generally only a concern with extremely high intake and an already low-iodine diet. For individuals with adequate iodine intake, eating these foods as part of a balanced diet poses no significant risk.

Conclusion: Ensuring Adequate Iodine from Plant Sources

For those seeking reliable plant-based iodine sources, sea vegetables are the most effective option, with species like nori and wakame providing consistent levels. Kelp should be consumed with caution due to its high, variable concentration. Land-based plants offer minimal iodine, making them unreliable for meeting daily requirements. Fortified plant-based milks and, most importantly, iodized salt provide consistent and easily accessible sources of the mineral. By incorporating a variety of these foods and checking labels for fortification, it is entirely possible to meet daily iodine needs through a plant-based diet.

For more information on iodine requirements and general nutrition, consult the National Institutes of Health.

Frequently Asked Questions

Kelp, a brown seaweed, is the most potent plant source of iodine, though its content can vary significantly depending on where and when it was harvested.

No, the iodine content in land-based plants is highly inconsistent and dependent on the soil composition where they were grown, making them an unreliable source.

Kelp contains extremely high levels of iodine and can be unsafe, especially in supplement form, due to its variable and potentially excessive concentration. Health bodies advise caution, especially for pregnant women.

Vegans can get adequate iodine by incorporating small, regular amounts of seaweed like nori, using iodized salt, and choosing plant-based milks that have been fortified with iodine.

No, most specialty salts like sea salt, Himalayan salt, and kosher salt are not fortified with iodine. Only products specifically labeled as 'iodized' can be relied upon for iodine content.

For individuals with adequate iodine intake, goitrogens in foods like soy and cruciferous vegetables are not a significant concern. They only become problematic with very high intake alongside pre-existing low iodine levels.

While not primary sources, fruits like strawberries and cranberries can contribute small amounts of iodine to a varied diet. However, they should not be considered a main source.