Iodine and Thyroid Health

There’s a lot of controversy around iodine and thyroid health, and many thyroid patients are unsure whether to increase their iodine intake with food and supplementation or avoid getting too much of it. Some consider adopting a low-iodine diet and avoiding iodine-rich foods like seaweed, fish, and iodized salt. 

However, the answer isn’t so clear-cut! It really depends on whether someone has autoimmune thyroid disease, an increased risk of developing Hashimoto’s, or non-autoimmune hypothyroidism. Iodine excess can harm the thyroid, but so can an iodine deficiency!

Let’s take a closer look at the link between iodine and thyroid health, and discuss why your need for iodine probably lies somewhere in the middle.

Iodine is essential for thyroid function

Before we discuss the link between iodine and thyroid dysfunction, I’d like to make one thing clear: some iodine is essential for thyroid health. In fact, iodine deficiency is the leading cause of hypothyroidism globally, and the prevalence of hypothyroidism decreases in iodine-sufficient populations. 

Like other trace minerals, we require small amounts of iodine throughout all life stages — including gestation, infancy, childhood, and adulthood. This is because iodine is an essential cofactor for thyroid hormone production, secretion, conversion, and metabolism (along with other nutrients like selenium, zinc, and iron). 

The thyroid gland uses iodine to synthesize thyroxine (T4) — the thyroid hormone that converts to triiodothyronine (T3) — its biologically active form. In the event of iodine insufficiency; however, the thyroid gland cannot adequately synthesize T4. The pituitary gland increases its production of thyroid-stimulating hormone (TSH) in response to this, leading to persistently elevated TSH levels. This tends to happen when daily iodine intake falls below 100 mcg

When TSH levels are persistently elevated and patients remain deficient in iodine, thyroid dysfunction (e.g. goiter, thyroid nodules, and hypothyroidism) often occurs. However, a patient’s daily iodine intake typically needs to fall below 10 or 20 mcg in order for hypothyroidism to develop. 

How much iodine per day is recommended?

Although we need at least 100 mcg of iodine daily to support thyroid function, the World Health Organization (WHO) recommends a daily intake of:

  • 90 mcg from birth through age five.
  • 120 mcg for children ages six to 12. 
  • 150 mcg for everyone 12 and older.
  • 250 mcg for pregnant and breastfeeding women (in contrast, the U.S. Institute of Medicine recommends 220 mcg of iodine in pregnancy and 290 mcg during lactation).

A daily intake of 150 to 300 mcg is likely safe for most adults, but this is where things get confusing. Excess iodine can be just as harmful to the thyroid gland as an iodine deficiency, and the American Thyroid Association (ATA) warns against ingesting more than 1,100 mcg daily. And if you’re taking kelp or iodine supplements, the ATA advises against ingesting more than 500 mcg daily.

The thyroid gland requires iodine to function, but it needs just the right amount. Not too much or too little!

Excess iodine and Hashimoto’s disease

Much of the controversy around iodine and thyroid health has to do with autoimmune thyroid disease (or Hashimoto’s autoimmune thyroiditis). This is because iodine excess may increase the risk for Hashimoto’s and subclinical hypothyroidism, or worsen existing thyroid symptoms. Iodine intakes of more than 300 mcg daily are generally deemed excessive and could be associated with autoimmune thyroid disease.

To support thyroid function without increasing the risk of autoimmune thyroid disease, anyone who has (or suspects they have) Hashimoto’s may want to avoid consuming more than 150 mcg of iodine daily. This doesn’t necessarily mean adopting a low-iodine diet, though. Remember: the thyroid gland requires some iodine and we don’t want to avoid it altogether!

Iodine and hypothyroidism: where to go from here

If you have hypothyroidism, there’s a chance you could be deficient in iodine — especially if you’re vegan, vegetarian, or don’t eat a lot of iodine-rich foods like seaweed, cod, tuna, shrimp, eggs, and iodized salt. Other symptoms of iodine deficiency include the development of a goiter and impaired mental function. 

That said, this doesn’t mean you should over consume iodine-rich foods or supplements, either — as iodine excess can also cause thyroid dysfunction and possibly lead to autoimmune thyroid disease. While iodine supplementation may be necessary in some cases, it’s best to work with a medical practitioner to determine the best course of action.

Book Your Naturopathic Functional Medicine Visit!

In my naturopathic functional medicine practice, I offer in-depth and specialized testing, nutrient supplements, diet and lifestyle recommendations, and many other services so we can identify and address the potential causes of your symptoms or health condition. Every patient is unique, and because of this, every treatment plan should be, too. Book an appointment with me online or by calling +971-800-6686.

Do you suspect you could be deficient in iodine or another essential thyroid cofactor?

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