To be honest, I never worried about iodine until I became vegan. While it might not be as buzzworthy as protein or iron, iodine is an essential trace element that plant-based eaters, like everyone else, need to maintain their well-being.

Iodine plays a crucial role in regulating our metabolism and supporting overall thyroid function, which influences everything from energy levels to brain development. But here’s the issue: iodine predominantly finds its way into our diets through seafood and dairy products – staples absent from the vegan plate.

Fear not, fellow plant-based enthusiasts! This blog is your compass to navigate the sea of vegan iodine sources, providing insights, practical tips, and when to supplement.

What Is Iodine?

Iodine is an essential trace mineral, which means it’s required by the body in relatively small amounts. Since your body is unable to make iodine it is essential that you obtain it either from your diet or from a supplement.

Why Iodine Is Essential for Our Health:

Thyroid Function

One of the primary roles of iodine in the body is in the synthesis of thyroid hormones, thyroxine (T4), and triiodothyronine (T3).

These hormones are produced by the thyroid gland, a butterfly-shaped organ located in the neck, and they play a fundamental role in regulating the body’s metabolism.

Thyroid hormones influence the rate at which the body uses energy, regulates body temperature, and supports the growth and development of various organs, including the brain and the nervous system¹.

Brain Development

Iodine is particularly critical for pregnant women and infants. During pregnancy and early infancy, adequate iodine intake is vital for proper brain development.

Iodine deficiency during this period can lead to cognitive impairments, stunted growth, and intellectual disabilities in children².

Immune System Support

Iodine not only has been shown to have antimicrobial properties, but it can help support the body’s immune system by fighting off infections and protecting against various pathogens³.

How Much Iodine Do You Need?

The RDA (Recommended Dietary Allowance) for iodine is 150mcg daily for both men and women (19 years and older) and 220 and 290 mcg daily for pregnant and lactating women.

How Much Is Too Much?

It appears that high iodine intake for most healthy people is well tolerated. However, those who have autoimmune thyroid disease or have a history of iodine deficiency can be more sensitive to excessive iodine intake⁴.

Iodine toxicity or getting too much iodine can ironically cause some of the same symptoms as iodine deficiency such as hypothyroidism as well as leading to too much thyroid hormone production (hyperthyroidism).

The recommended tolerable upper intake limit set at no more than 1100mcg per day including both diet and supplement sources.

For sensitive individuals there appears to be a fine line of getting enough and getting too much. Even small increases over the RDA could cause problems⁴.

Iodine Deficiency

Iodine deficiency is a lot more common worldwide. For adults, an iodine deficiency (an intake of less than 10-20 mcg a day) can lead to inadequate thyroid hormone production, causing hypothyroidism⁵. This can lead to various symptoms such as:

• Fatigue
• Weakness
• Sensitivity to cold
• Weight gain
• Constipation
• Dry Skin
• Hair Loss
• Goiter (a lump or swelling of the neck)

Adequate iodine intake is essential for proper metabolism, brain development, immune system function, and many other critical processes in the body.

A deficiency in iodine can lead to a range of health issues, including hypothyroidism, goiter (enlargement of the thyroid gland), intellectual disabilities in children, and metabolic imbalances.

Why Are Vegans at Risk For Iodine Deficiency?

Seafood, Dairy & Egg Exclusion

Some of the major sources of iodine come from white fish and shellfish (cod, haddock, pollock, oysters, shrimp), eggs and dairy. If you are vegan you do not eat any of these foods.

One of the main reasons why milk and dairy products can contain a lot of iodine is that cows often receive iodine feed supplements and an iodine containing udder disinfectant (used to prevent mastitis infections) which contribute to the milk’s iodine content⁴.

Reduced Iodized Salt Intake

Many people get a significant portion of their iodine from iodized table salt. However, many vegans often use alternative, non-iodized salts, such as sea salt or Himalayan salt, which contain little to no iodine.

The Dietary Guidelines for Americans recommends adults limit sodium intake to less than 2,300 mg per day which is equal to about 1 teaspoon of table salt.

So, for those who are more conscious about their sodium intake and are not adding table salt to their food would not be getting in enough iodine this way.

Variable/Low Iodine Content of Plant Foods

Most grains and commercially prepared bread in the United States contains very little iodine unless the manufacturer has used potassium iodate or calcium iodate as a dough conditioner.

Fruits and vegetables are typically poor sources of iodine and the amount can be highly variable. This is because the iodine content depends on the amount of iodine in the soil and fertilizer used.

So, in general, most plant-based foods are not rich sources of iodine.

Goitrogens, Iodine & Thyroid Function

You might have heard that certain plant foods like soy and cruciferous vegetables – otherwise known as “goitrogens” can interfere with the uptake of iodine in the thyroid causing hypothyroidism.

This is a hypothesis based on animal studies and there are actually no human studies backing this up unless you are consuming massive amounts of these foods in addition to being iodine deficient⁶,.

You might think that vegans and vegetarians would have higher risk of hypothyroidism due to their higher intake of plant foods and lower intake of iodine. The Adventist Health Study-2 assessed the risk of hypothyroidism in those on a vegan and vegetarian diet compared to omnivores and a vegan diet tended to be associated with lower, not higher, risk of hypothyroid disease.

Cruciferous vegetables and natural soy foods rich in isoflavones offer a lot of health benefits and can be protective against certain cancers including thyroid cancer⁷. For more on soy and thyroid function you can check out the blog: Pros and Cons of Soy.

Bottomline, ensure you are meeting your iodine needs either through diet or supplements and don’t eat extreme amounts of any food and goitrogens should not pose any problems.

The Best Vegan Sources of Iodine

Iodized Salt

As previously mentioned, you can add table salt fortified with iodine to meet your needs. You would need to add about 1/2 teaspoon daily to give you around 150mcg.

If you’re not salt sensitive or don’t have blood pressure issues this might be an option for you, however, I don’t believe this is the healthiest way to meet your iodine needs.

Sea Vegetables or Seaweed

Sea vegetables are a rich source of iodine. The majority of Americans are not used to consuming very many sea vegetables in comparison to other countries throughout Asia. A few good examples would be nori, kombu, kelp, and wakame.

Wakame is often used in seaweed salad or miso soup. You would really only need around 1 Tbsp (5g) to meet the RDA for iodine.

Nori is a popular seaweed used to wrap sushi rolls or are often made into roasted snack sheets. The iodine content in nori varies (~16-43 mcg/g), so eating around 2 sheets of nori would do the trick. Nori sheets are usually around 3g each.

Another option is using dulse flakes in place of salt to flavor a meal. Different brands vary, but if you used Main Coast Dulce Granules you would only need about 1/2 teaspoon which would provide close to 150mcg with minimal sodium.

The challenge would be to find a way to use it on a regular basis. I tried using dulse but found that I ended up rarely using it.

There are a few problems, however, with relying on sea vegetables for your iodine intake.

The iodine content of sea vegetables is highly variable with some sources like Kombu (kelp) containing very high amounts of iodine. Just a small 1g sheet could contain close to 3,000 mcg and 1g of kelp flakes providing over 8,000 mcg of iodine⁵!

For people with thyroid issues I would not recommend using kombu or kelp as even small amounts can significantly exceed the RDA of 150 mcg. I would also avoid hijiki which can contain toxic amounts of arsenic.

When To Supplement With Iodine

If you are following a plant-based or vegan diet and do not use iodized salt or consume dulse flakes or other sea vegetables on a regular basis it might be prudent to take a daily supplement.

Supplementing up to the RDA amount of 150 mcg daily is what is usually recommended. Many vegan multivitamins contain iodine. This is something that I take myself just to ensure that I’m getting enough.

It’s always a good idea to discuss supplementation with your doctor before starting on a new supplement.

Iodine Summary

We learned that iodine is an essential trace mineral that your thyroid depends on for the production of thyroid hormones and is also critical for brain development and can provide support to our immune system.

You probably noticed that if you are following a plant-based or vegan diet that there are very few foods that you can count on providing you with adequate amounts of iodine.

Two of the best vegan sources of iodine are sea vegetables and iodized salt. Sometimes taking a supplement might be necessary and that’s OK!