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Best Plant-Based Sources of Iodine

What is iodine?

Plantz Matter: Seaweed vegan sushi

It is a chemical element that belongs to the halogen group in the periodic table. This element is essential to produce thyroid hormones, which regulate the body's metabolism and growth. It occurs naturally in seawater, some minerals, and in soil. It can be obtained through dietary sources such as seafood, fish, seaweed, and iodised salt. But what plant-based sources have the best iodine content?

Why is iodine important?

It is needed for the following roles:

  • Thyroid health

  • Metabolism and growth

  • Brain development and function

  • Nervous system function

It's necessary for the human body to produce thyroid hormones, which are critical in regulating the body's metabolism and growth. These hormones are essential for the normal development and function of the brain, nervous system, and other organs.

Iodine deficiency during pregnancy and infancy can harm a baby's brain development. Without enough, the thyroid gland can become enlarged, leading to a goitre. Severe iodine deficiency can also result in mental delay, cretinism, and other developmental disorders.

What are the symptoms and consequences of iodine deficiency?

You may develop an iodine deficiency if you don't have a regular intake. Deficiency could have negative health consequences. Some of the more common are:

Cognitive impairment: Deficiency during pregnancy and early childhood can lead to cognitive impairment and developmental delays in children.

Cold intolerance: Iodine deficiency can cause sensitivity to cold temperatures, as the thyroid hormones help regulate body temperature.

Dry skin and hair: Iodine deficiency can cause dry skin and hair, as the thyroid hormones help regulate skin and hair growth.

Fatigue: Iodine deficiency can cause fatigue and weakness, as the thyroid hormones help regulate energy metabolism.

Goiter: The thyroid gland enlarges, which can lead to visible neck swelling.

Hypothyroidism: It is an essential nutrient that is required for the production of thyroid hormones. Thyroid hormones are synthesised in the thyroid gland by combining iodine with the amino acid tyrosine.

In the case of a deficiency, the thyroid gland may not be able to produce enough thyroid hormones, leading to a condition called hypothyroidism.

Hypothyroidism is, therefore, a condition where the thyroid gland is underactive and does not produce enough thyroid hormones. Deficiency can cause symptoms such as fatigue, weight gain, dry skin, constipation, depression and cold intolerance.

Increased risk of thyroid cancer: Deficiency may increase the risk of developing thyroid cancer.

Mood changes: Iodine deficiency can lead to changes in mood, including depression and anxiety.

Weight gain: Iodine deficiency can lead to weight gain or difficulty losing weight, as the thyroid hormones regulate metabolism.

What is the daily intake and how much iodine do I need in my diet?

Iodine is stored in the thyroid, so you don't need to eat it daily. However, there are daily recommendations that alter due to age, gender, and other factors. The standard daily iodine intake for different age groups:

  • Children 1-8 years: 90 mcg

  • Children 9-13 years: 120 mcg

  • Adolescents 14-18 years: 150 mcg

  • Adults 19 years and older: 150 mcg

  • Pregnant women: 220 mcg

  • Breastfeeding women: 290 mcg

The upper intake level (UL) for iodine is 1,100 mcg per day for adults, meaning that if you consume more than this, iodine can harm your health.

How Common is iodine deficiency?

Inadequate iodine intake can cause iodine deficiency. It is rarer in developed countries as many foods contain it, and iodised salt is readily available. However, iodine deficiency can still happen in specific populations, particularly in areas where the soil is iodine-poor and in individuals who do not eat a varied and nutrient-rich diet.

Can I get too much iodine?

Iodine excess amounts are rare in individuals who consume a balanced diet. Still, it can occur in individuals who consume excess amounts of iodine supplements or foods very high in iodine, such as kelp or supplements.

The tolerable upper intake level for iodine is 1,100 mcg per day for adults, and consuming more than this amount can be harmful. If you think that you have consumed excess amounts and or are experiencing symptoms raise your health concerns with a professional.

Symptoms of too much iodine:

  • Nausea and vomiting

  • Diarrhea

  • Abdominal pain

  • Headaches

  • Metallic taste in the mouth

  • Burning sensation in the mouth and throat

  • Thyroid dysfunction, such as hyperthyroidism or hypothyroidism

  • Goiter

  • Acne-like rash

  • Swelling of the salivary glands

  • Eye irritation and tearing

  • Fever

Here are some of the most common effects of iodine excess in more detail:

Thyroid dysfunction: Consuming excessive amounts of iodine can cause the thyroid gland to become overactive or underactive, leading to symptoms such as anxiety, weight loss or gain, and irregular heartbeat.

Acne and skin rashes: Excess iodine intake may cause acne or other skin problems.

Gastrointestinal symptoms: Consuming too much iodine can cause stomach upset, nausea, vomiting, and diarrhoea.

Increased risk of autoimmune thyroid disease: Some studies suggest excessive iodine intake may increase the risk of autoimmune thyroid diseases such as Hashimoto's thyroiditis and Graves' disease.

Are there specific groups of people at higher risk of iodine deficiency?

Certain groups should monitor their iodine intake:

  • Pregnant and breastfeeding women need more iodine to support the development of their infant's brain.

  • Infants and young children have higher iodine needs for their brain development and may be at risk of deficiency if they do not get enough from breast milk, formula, or solid foods.

  • People live in specific geographic locations where the soil is iodine deficient. If the soil is deficient, the food grown there will be, as well as the people consuming the produce unless they get iodine from an alternative source.

  • People who do not eat enough iodine-rich foods. This mainly refers to those who avoid salt, do not eat seaweed or sea vegetables, and only eat whole, unprocessed plant foods. Who are these people? Unfortunately, many vegans fall into this category as they do not reach their daily recommendations.

Vegetarians and milk drinkers are not at as much risk as dairy cow utters are dipped in iodine for hygiene and infection prevention. This iodine makes its way into the milk supply.

What are plant-based dietary sources of vegan sources?

Can you get enough iodine on a plant-based diet or vegan diet? Yes, iodine for vegans is pretty easy if you know how.

Plant sources of iodine (vegan foods):

Plantz Matter  kelp, nori and dulse mixed seaweed

Eat your seaweed and sea veggies: They are major sources. Seaweed and sea vegetables have good iodine content. They are the best way to improve your iodine levels. Iodine in seaweed can vary depending on type, growing and processing.

Be careful with the amount of seaweed and sea vegetables you consume, as they can be high in iodine, and excess iodine can lead to iodine toxicity. Kelp is a very high source of iodine. It can contain up to 2000 mcg per tablespoon! 

Thinking about this, vegan iodine supplements such as kelp supplements seem to be like something to be wary of. Be careful with products like kelp meal and daily supplements.

Dr Greger (and many governments worldwide) warn against eating hiziki (hijiki) as it can contain arsenic.

To meet daily recommendations, choose one of the following vegan iodine sources:

  • 1 tsp of arame

  • 1 tbsp seaweed salad

  • 2 sheets of nori

  • 1 tsp dulse

More Plant Sources of Iodine

But wait there are many more plant sources of iodine:

Infographic Plant-based vegan sources of iodine

Fruits and vegetables: Some fruits and vegetables are good sources of iodine, such as potatoes, strawberries, and cranberries. Cranberries, fresh or frozen, can provide a small amount of iodine and other antioxidants and nutrients.

Dried prunes are another source of iodine; levels vary depending on the brand and the processing methods used.

Iodine-fortified foods: Many processed foods are sources of iodine (that's one point to junk food vegans). Dr Greger appears to be disappointed in a video on iodine that only a few plant-based milks manufacturers have cottoned on to the need for iodine fortification.

Use iodised salt: If you must use salt, go for iodised salt, but don't overdo it. Salt comes with its risks.

Can iodised salt meet my daily diet needs?

Iodised salt can be a good source and help you meet your iodine needs. In some countries, iodine deficiency was a significant public health concern before iodised salt was introduced as a means of prevention.

Iodised salt is ordinary table salt that has been fortified. Iodised salt contains approximately 45 micrograms of iodine per gram of salt.

That's all well and good, but salt is still salt, which is bad if you have too much. Salt can:

woman on bathroom scale
  • Salt can raise blood pressure

  • Cause bloating and water retention

  • Disrupt mineral balance in the body

  • Contribute to kidney stones

  • Increase the risk of stomach cancer

  • This can lead to weight gain by creating cravings leading to overeating

  • Impair blood vessel function

  • Worsen asthma and Meniere's disease

  • Increased risk of osteoporosis

  • Cause dehydration

Should I take an iodine supplement?

Most people in developed countries can meet their needs with diet. High doses of can be harmful, so if you are in an at-risk group or have concerns about your iodine levels, please discuss the topic with your doctor before taking any supplements.

Then together, you can decide the best course of action for your circumstances. Iodine supplementation should only be used after testing your levels and at the suggestion and supervision of your healthcare provider.

Are there any interactions between iodine and other nutrients or medications?

Iodine does interact with other nutrients and medications:

  • Thyroid medications

  • Selenium can intensify the negative impacts of iodine, especially on the thyroid.

  • Reduces absorption of lithium and possibly other medications used to treat mental health.

How is iodine deficiency diagnosed? Are there any tests for iodine levels?

Woman curled up on bed feeling ill

There are several ways medical professionals can help diagnose an iodine deficiency:

Physical examination

  • A physical examination can diagnose a goitre, a visible enlargement of the thyroid gland in the neck.

  • A healthcare provider may also ask about symptoms of hypothyroidism or hyperthyroidism, such as fatigue, weight gain or loss, and sensitivity to cold or heat.

Medical history

  • A healthcare provider may also ask about your medical history, including any history of thyroid disease, iodine exposure, or dietary habits that may affect iodine intake.

Laboratory tests

  • Blood tests can measure thyroid function. It can measure levels of thyroid hormones, including TSH (thyroid-stimulating hormone), T4 (thyroxine), and T3 (triiodothyronine). Low levels of these hormones may indicate hypothyroidism, which can be caused by iodine deficiency.

  • Urine tests can also be used to measure iodine levels in the body. However, measuring iodine levels in urine is only sometimes a reliable indicator of iodine status, as iodine levels in urine can fluctuate depending on recent dietary intake.

  • Ultrasound or a thyroid scan may also be ordered to assess the size and function of the thyroid gland.

How long does it take to correct iodine deficiency once dietary changes are made?

Unfortunately, there is no simple answer to this question. The time it takes to get your iodine levels back into a healthy range depends on the severity of the deficiency, how you address it (diet or medical treatment) and individual factors such as age and health.

Increasing your intake of iodine may take a different amount of time for each symptom to resolve. Some symptoms may persist even after iodine levels return to normal; additional treatment or management may be necessary to address these symptoms.


The vegan diet is not devoid of iodine. Many plant-based foods have a good amount of iodine content. So it is easy to get an adequate iodine intake without animal sources such as fish. It is a myth that you need animal foods like white fish or dairy to get iodine. The risk of iodine deficiency is low on a balanced plant-based diet.

It is an essential element our body needs to function. Sources should not be added daily but regularly consumed to maintain healthy levels. While iodine deficiency is rare in developed countries, several groups need to be mindful of their intake either because they have a higher requirement, or their diets do not include enough iodine without consuming iodine-rich sources.

An easy way to increase your iodine levels is iodised salt, but the healthiest way is to include seaweed or sea vegetables. For more on seaweed, read my article Are You Seaweed Savvy?

If you found the information in this post useful, please help me spread the word and share it. Thanks for reading and remember to eat your seaweed.


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