November 29


Important Reasons Why Your Thyroid Needs Iodine

Iodine is crucial for thyroid health. Learn all about iodine and how to make sure you are getting enough to improve thyroid symptoms.

By Amy Vespa, MS - Integrative Clinical Nutritionist

November 29, 2021

minutes read time


If you have thyroid issues you have definitely heard of iodine. And you’ve also probably noticed it can be a controversial topic. 

This controversy stems from over 100 years ago. Back in the early 1900s, goiters caused by iodine deficiency were common. Governments around the world recommended (or required) adding iodine to table salt. This greatly reduced goiter prevalence in the population.

However, later it was found too much iodine was linked to higher rates of Hashimoto’s. 

Supplementation can be beneficial to thyroid health. But there are instances where restriction can improve Hashimoto’s symptoms.

This fine line of what is beneficial and what is harmful makes iodine a confusing nutrient to understand!

Let’s dive into why it is important, how to know if you need it, and how to get the right amount for you. After reading this article you will have a much better understanding of how to supply your body with just what it needs.

Iodine and the thyroid

Iodine is an essential trace element, meaning we need just a little from our food but that little bit is crucial for health. 

About 70-80% of iodine is in the thyroid. And iodine is a key part of the thyroid hormones T3 and T4. A deficiency impairs the body’s ability to make thyroid hormones, causing hypothyroidism and goiter. It is also important during pregnancy and lactation for the development and growth of the baby.

Symptoms of low iodine are similar to those for hypothyroidism:

  • headaches
  • fatigue
  • memory problems
  • hair loss
  • goiter / neck swelling
  • sensitivity to cold
  • brain fog
  • and more…

On the flipside, symptoms of excess are:

  • fatigue or muscle weakness
  • goiter / neck swelling
  • nausea
  • diarrhea
  • increased heart rate

Kinda similar right? 

The best thing to do before taking iodine is to get your levels checked. Through your doctor ask for:

  • a 24-hour urine test which will indicate recent intake (If you ate fish yesterday for the first time in months, your urine will still show higher iodine. But if you have been eating the same foods consistently, then this test would be more reliable.)
  • serum Tg (thyroglobulin) – higher levels can show deficiency
  • serum selenium

Selenium and iodine work together for thyroid health. And deficiency or excess of one affects the other.

Iodine is a crucial part of thyroid hormones T3 and T4. And selenium is a main part of the enzyme that converts T4 to T3. It’s important to understand this relationship before considering supplementation.

Without one nutrient, the other can’t do its job, leading to lower thyroid hormone production. While too much of either can cause problems too. 

Make sure you are getting enough

Because iodine is so important, how can you know if you are getting enough (but not too much)? 

First, the risk factors for iodine deficiency are: 

  • not eating iodine rich foods
  • selenium deficiency
  • smoking
  • eating too many raw goitrogenic foods
  • digestion issues (not absorbing your nutrients)

A big risk factor is impaired digestion. If you eat a good amount of iodine-rich foods but have difficulty with digestion (constipation, diarrhea, pains, bloating, acid reflux, etc.) then your body might not be absorbing enough.

Next, do you eat any of these foods with iodine:

  • seafood, especially cod, haddock, oysters, mussels, shrimp
  • seaweed (can vary widely based on type, see below)
  • iodized salt
  • egg yolks
  • milk (cow)
  • potatoes with peel
  • navy bean
  • turkey breast

The best type of seaweed to include?

Per gram – kombu has the most at 1,682% of the daily value (DV), wakame has 93% DV, nori has 24.6% DV. The popular dried seaweed sheet snacks are usually nori.

A note on salt: The only salt that has substantial iodine is ‘iodized salt’ which will be labeled as such. Sea salt, Himalayan salt, or other specialty salts do not have substantial iodine. 

Before you go out and buy iodized salt, know that using iodized salt daily can cause iodine excess. You only need ¼ teaspoon of iodized salt to get enough iodine.

What to do about iodine

Now you know a lot more about iodine! This is one of the few nutrients that you really have to be careful with the ‘more is better’ philosophy. BUT getting that right amount for great thyroid health is not that hard.

To get a good amount in your diet, enjoy the foods that contain a known amount of iodine. Eggs, fish, potatoes, navy beans, dry seaweed strips throughout the day and week. The occasional seaweed salad would be good too. 

Unless you’re eating seaweed salad and fish as a huge part of your daily diet, you will likely not go overboard with iodine.

Supplementing with iodine can be done safely with the help of a health care professional and monitoring your levels and how you feel.

Below, I’ve provided a cheat sheet giving you the best foods that contain iodine and the amounts. Enter your name and email address below and it’ll show up in your inbox shortly!

In the comments, let me know when is the last time you’ve had your iodine levels tested.

Additional sources:

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