Can vegan food rich in iodine affect thyroid? What about iodized salt?

Iodine-rich-foods. Health benefits and side effects

Iodine is a trace element. Certainly, iodine is good for you, but we need only a little. As there are many iodine-rich foods we can easily exceed the daily value. Iodine toxicity can be as harmful as iodine deficiency.

Why do we need iodine?

Iodine is a key component for the proper development of fetuses and infants.

Moreover, it’s important for the proper production of thyroid hormone.

What does iodine do in the body?

Additionally, iodine can play a role in the immune response of the body.

Also, studies have shown that iodine may help with mammary dysplasia and some breast diseases.

Health benefits of Iodine

Firstly, iodine is necessary for proper fetal and infant development.

For example, iodine deficiency can cause mental retardation.

For these reasons, the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) recommend a daily iodine intake for pregnant and lactating women of 250 mcg (1,2).

Why iodine deficiency is dangerous?

If a pregnant woman has iodine deficiency can cause irreversible health effects to the fetus.

Additionally, the health of a young infant is also vulnerable to iodine deficiency.

Another effect of iodine deficiency may be the increased risk for attention deficit hyperactivity disorder among children.

On the other hand, adequate amounts of iodine can improve cognitive function in iodine-deficient kids. 

Adults are also vulnerable to iodine deficiency, as a deficiency can cause (2):

  • goiter,
  • impaired mental function,
  • impaired work productivity, and
  • even increased risk of thyroid cancer

Last, but not least, iodine is so important in thyroid hormone production…

Iodine and thyroid

Iodine is essential for the proper production of the thyroid hormones.

These thyroid hormones are responsible for:

  • protein synthesis,
  • metabolic activity,
  • enzymatic activity.

Especially in fetuses and infants, thyroid hormones are important for their:

  • skeletal development and
  • central nervous system development

But, why iodine is so important?

When the body experiences iodine deficiency, we have goiter. A goiter is an abnormal enlargement of your thyroid gland. This way the body tries to trap more iodine. The iodine is necessary for the production of thyroid hormones.

Contrary, iodine toxicity can cause the same symptoms as iodine deficiency. Goiter is the most common. Keep in mind that high amounts of iodine can inhibit thyroid hormone synthesis.

Recommended Daily Intake

The recommended daily intake of iodine for adult men and women is about 150 mcg.

Infants and children need about 90 – 130 mcg.

Pregnant and lactating women have even higher iodine needs.

Women in pregnancy need about 220 mcg. Lactating women need a slightly higher amount of 290 mcg daily.

How much iodine is too much?

It is advised not to consume more than 1100 mcg of iodine daily. It’s the upper intake level for adults. Kids and teenagers tolerate even less.

If someone keeps consuming too much iodine, for a long time, it’s possible to experience health problems.

Only people who receive medical treatment can exceed this limit. Always consulting a physician.

Symptoms of too much iodine

If you consume daily foods rich in iodine, it can be dangerous for health.

High intakes of iodine, at a long term, can cause the same symptoms as iodine deficiency:

  • goiter,
  • elevated TSH (Thyroid Stimulating Hormone) levels, or
  • hypothyroidism

What’s the most common source of iodine?

The most common source of iodine is salt. Not sea salt though…

Does sea salt have iodine?

Sea salt comes from the evaporation of saltwater lakes or sea. Companies promote it as the healthiest salt, as sea salt usually hasn’t been processed heavily.

Sea salt is rarely fortified with iodine though. The amount of iodine in unfortified sea salt depends on the water source. In any case, it’s rather small.

Furthermore, sea salt and table salt have similar nutritional value.

Why iodine is added to salt?

Iodized salt is the most widely used strategy to prevent iodine deficiency.

About 70% of people worldwide consume iodized salt.

People in America use mostly iodized salt (about 90%). Contrary to 50% in Europe.

Benefits of iodized salt

Just 1.5 gr of iodized salt or 1/4 teaspoon provides us with 71 mcg of iodine. That’s about 47% of Daily Value.

It’s an effective and cheap way to deal with iodine deficiency.

Especially in regions that food is low in iodine. For instance, mountainous areas are usually such regions.

But, keep in mind that the majority of the daily salt intake comes from processed foods.

Food companies don’t use iodized salt, though. If they do, you’ll see it in the ingredient list. They have to refer that the salt is iodized.

Of course, you shouldn’t overdo it with salt. Increased salt consumption has linked to the increased risk of some cancers.

Does pink Himalayan salt have iodine?

Himalayan salt has gained popularity, as it is believed to have many health benefits.

Himalayan salt has more minerals and trace elements than table salt. That’s the reason people believe it’s better.

The truth is that both pink Himalayan salt and common table salt consists mostly of sodium chloride.

As sodium chloride is essential for many of our body’s functions, the supposed health benefits of Himalayan salt may be the same as any salt. Table, sea, or Himalayan salt…

The amounts of the other minerals of Himalayan salt are so small that they are negligible.

Most noteworthy the pink Himalayan salt usually contains less iodine than iodized salt.

Maybe a good reason to prefer Himalayan salt is if you want to avoid any additives. Some table salts may contain additives. Sea salt and Himalayan salt are considered the purest salts.

If you prefer Himalayan salt, take extra care of the iodine-rich foods, to avoid iodine deficiency. Because table salt can be the main source of iodine for many people.

What foods have iodine?

Deficiency of iodine is rare in developed countries. Partially because of the usage of iodized salt.

But, many foods contain adequate amounts of iodine:

  • seafood is a good source of iodine. For instance, cod (99), shrimp (35), and canned tuna (17) are all iodine-rich foods. The values are mcg per serving.
  • dairy is also rich in iodine. The main reason is the use of iodine feed supplements though…

Vegan iodine-rich foods

Are there any vegan foods that are actually rich in iodine?

Seaweed and algae are rich in iodine

In a matter of fact, the iodine-richest food is actually vegan. It’s seaweed.

Popular algae and seaweed are kelp, nori, kombu, wakame, dulse, spirulina, and chlorella.

We should be extra cautious when consuming seaweed. Its content of iodine is highly variable. Just 1 gr of seaweed can provide us from 16 to 2984 mcg of iodine. That’s from 11% to 1989% DV.

This can be dangerous. Remember…We need iodine, but just a small dose (150 mcg). Excess iodine may cause hyperthyroidism or even thyroid cancer. According to the Food Nutrition Board, we shouldn’t consume more than 1100 mcg daily, for a long time (2).

The problem with seaweed is that its iodine content is highly demanding in many conditions:

  • sea and water region,
  • variety,
  • process method
  • storage conditions (may vaporize).

Does kelp contain too much iodine?

For instance, kelp may contain from to 514 mcg to 6571 mcg of iodine per gram. That’s depending on the preharvest conditions. Kelp that has been sun-bleached has the lowest amount. Contrary, fresh kelp has the highest (3).

Kelp is algae. It grows only in the sea and it is super-rich in iodine. Even a quarter gram of kelp can excess upper intake.

You better avoid it. The health risks are greater than the probable health benefits…

Are all seaweed or algae rich in iodine?

There are other safer seaweed options:

  • kombu. Kombu is an edible kelp. It’s super-rich in iodine. Just 1 gram of kombu contains about 1542 – 5307 mcg of iodine. You better avoid kombu, as you can easily exceed the recommended daily iodine intake (150 mcg) and even the upper iodine tolerance limit (1100 mcg).
  • wakame. Wakame is a type of edible seaweed. It’s part of the traditional Japanese cuisine. Wakame is used as a sea vegetable. Wakame doesn’t contain so much iodine as kombu. It has about 60 – 1571 mcg of iodine per gram. It may be a good idea to avoid consuming it on a regular basis.
  • nori. Nori and dulse are red seaweeds. They have lower iodine content. Usually, they have less iodine than 100 mcg per gram. The iodine content of nori depends on the nori variety and geographic location. It’s about 16 – 43 mcg per gram. So, you can consume nori safely, depending on iodine content.
  • dulse. Dulse, as nori, is a red edible seaweed. It grows in wild cold waters. Dulse’s main characteristic is its color. It has a beautiful red or purple color. Moreover, dulse is a good source of iodine. It contains about 44 – 72 mcg of iodine per gram. This means that dulse contains much iodine, but not too much… Due to dulse’s iodine content, you can consume it more often than other seaweeds or algae.
  • spirulina. Spirulina is a small, single-celled microorganism that’s rich in chlorophyll. It’s a type of blue-green algae, rich in minerals. Its iodine content can vary greatly. Some manufacturers market spirulina for thyroid support due to its iodine content. Others claim that their spirulina doesn’t contain any iodine. Consult your physical, if you have thyroid. Always read the nutrition list about iodine content.
  • chlorella. Chlorella is a single-celled algae. It grows in freshwater. Chlorella has a beautiful green color. Additionally, it’s very nutritious. Chlorella contains about 50% protein, minerals, vitamins, and many antioxidants. Chlorella may contain iodine. Usually, it contains only traces of iodine. Read the nutrition list of manufacturer, just to be sure. Seems like chlorella usually contains only about 2 mcg of iodine per gram (4).

Consequently, dulse, spirulina, and chlorella may be the safest options.

In any case, consult your physician if you have any thyroid issues.

Other common vegan iodine-rich foods

There are many vegan iodine-rich foods.

Firstly, there are many iodined-fortified products. Bread, spaghetti, fruit juices, or canned corn can be iodine-fortified. Just look at the nutrition facts.

Furthermore, other iodine-rich foods are:

  • Prunes. Just 5 prunes contain 13 mcg of iodine or the 9% DV.
  • Grains. For instance, just 1 cup of raisin bran cereal contains 11 mcg of iodine or the 7% DV.
  • Beans. Just 1/2 cup of lima beans contains 8 mcg of iodine or 5% DV.
  • Fruits. 1 cup of apple juice contains 7 mcg of iodine or 5% DV. Also, a banana contains about 3 mcg of iodine or 2% DV.

Fruits and vegetables contain iodine. But the iodine amount is highly dependent on:

  • the iodine content of the soil,
  • fertilizer use, and
  • irrigation practices.

Causes of iodine deficiency

Worldwide, iodine deficiency may still be a health problem.

It is estimated that 2.2 billion people in 47 countries live in areas with iodine deficiency. That’s 38% of the world’s population.

People who may experience iodine deficiency are those who:

  • don’t consume iodized salt,
  • live in regions with iodine-deficient soils. Iodine-deficient soils produce crops low in iodine,
  • live in mountainous regions. Mountains tend to poor in iodine,
  • eat many raw foods that contain goitrogen compounds. Goitrogens are substances that inhibit the absorption of iodine in the thyroid. Such foods are cruciferous vegetables.
  • don’t increase the iodine intake during pregnancy. Pregnant women demand more iodine daily. They should consume more iodine-rich foods. The recommended daily iodine intake increases from 150 to 220 mcg.

Do cruciferous vegetables cause iodine deficiency?

Cruciferous vegetables are the cabbage, collard greens, broccoli, Brussels sprouts, kale, kohlrabi, cauliflower, bok choy, mustard seeds, arugula, watercress, daikon, wasabi, spinach, swiss chard and many more.

Cruciferous vegetables are unique. They contain sulfur-containing compounds known as glucosinolates.

These dietary phytochemicals can decrease cancer risk. Sulforaphane has powerful antioxidant, anti-inflammatory, and anti-tumor properties. Sulforaphane has so many health benefits that have drawn the attention of researchers.

High intake of cruciferous vegetables has been associated with lower risk of (5,6,7,8,9):

  • lung cancer,
  • colorectal cancer,
  • breast cancer,
  • skin cancer,
  • stomach cancer,
  • diabetes,
  • brain diseases,
  • cardiovascular health.

Certainly, cruciferous vegetables promotes overall longevity.

So, could cruciferous vegetables be bad for you?

Cruciferous vegetables also contain natural goitrogenic compounds. Goitrogenic compounds can interfere with thyroid function though. These can inhibit the absorption of iodine from the thyroid.

Should we avoid cruciferous vegetables? Of course no…

Most noteworthy goitrogenic compounds are deactivated with cooking. If you cook your veggies you shouldn’t concern about the iodine absorption…

What about raw veggies?

You should consume considerable amounts of raw cruciferous vegetables to inhibit the uptake of iodine by the thyroid gland.

For instance, 1 kg of raw bok choy daily for several months could be dangerous for health (10). 

So, are vegan iodine foods good for you?

Iodine is certainly good for you…

Just remember… Too much iodine is as bad as too little…

You better:

  • consume iodine-rich foods such as whole grains and fruits,
  • avoid super iodine-rich foods such as kelp and nori,
  • cook your cruciferous vegetables,
  • or eat just a salad of cruciferous vegetables daily

Sources:

  1. World Health Organisation (WHO): Assessment of iodine deficiency disorders and monitoring their elimination (pdf)
  2. Iodine: Fact Sheet for Health Professionals
  3. NCBI: Variability of iodine content in common commercially available edible seaweeds (pdf).
  4. Chlorella and Spirulina Green Supplements for Balancing the Body (pdf).
  5. NCBI: Cruciferous Vegetables and Human Cancer Risk: Epidemiologic Evidence and Mechanistic Basis
  6. Trends in Cruciferous Vegetable Consumption and Associations with Breast Cancer Risk: A Case-Control Study
  7. Sulforaphane Protects against Brain Diseases: Roles of Cytoprotective Enzymes
  8. Pubmed: Cruciferous vegetable consumption is associated with a reduced risk of total and cardiovascular disease mortality.
  9. Division of Life Sciences, College of Life Sciences and Bioengineering, Incheon National University: Current potential health benefits of sulforaphane
  10. The New England Journal of Medicine: Myxedema Coma Induced by Ingestion of Raw Bok Choy