Seaweed, Iodine and The Thyroid

Thyroid location from

Firstly, what’s a thyroid?

The thyroid is a gland situated in the neck just below the Adam’s apple.

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Okay, and what's iodine?

Iodine is a mineral needed for normal thyroid function. It’s predominantly found in seaweed, fish and milk but also occurs in other foods.

Even in seaweed, iodine quantities vary by species, but overall it’s an excellent source.

iodine in food

What does my thyroid do with iodine?

It helps to play a very important role in maintaining normal cognitive function like thinking and problem solving. The thyroid maintains body temperature, controls your metabolism, regulates heart function and contributes to physical and cognitive growth and development in early life.

Wow! So what happens if my thyroid doesn’t function properly?

Some of the signs of an underactive thyroid, known as hypothyroidism, include decreased energy, dry skin, thinning hair and feeling cold all the time. Muscle aches and forgetfulness can occur too. In pregnant women, it can have severe effects on the cognitive development of children.

You can learn more about the effects of hypothyroidism in our case study on Mara Seaweed and thyroid dysfunction. 

Gosh. Is hypothyroidism common?

Well, the World Health Organisation has declared that the UK has a national problem of iodine insufficiency. And research papers in 2011 and 2014 identified 76% of British teenage school girls and 66% of adult women as iodine deficient.

Crikey. Should I be worried? How do I treat an underactive thyroid?

If your thyroid is borderline, or you have some of the symptoms, you may find consuming more iodine makes a big difference. In any case, prevention is better than cure.

Better get my iodine on then! What if I don’t eat dairy or animals?

Iodine can be manufactured and added to salt or taken in supplements. But seaweed is the most concentrated form of natural (chelated) iodine, easily absorbed by the body.

What kind of iodine isn’t easily absorbed by the body?

There are different types of iodine. Potassium iodide found in salt and supplements is absorbed very quickly and excreted again within three hours. However, natural iodine found in seaweed is absorbed by the body slowly and excreted over the next three days. This creates a much more stable, steady supply of iodine for the thyroid.

What’s the recommended daily intake (RDI) of iodine?

That depends on who you ask. There are two figures to take into account, RDI and Tolerable Upper Limit (TUL).

Recommended Daily Intake refers to “the daily intake which meets the nutrient requirements of almost all healthy individuals.” Tolerable Upper Limit  (TUL) refers to “the highest average daily nutrient intake level unlikely to pose risk of adverse health effects to almost all healthy individuals.”

The World Health Organisation has set an RDI of 150 micrograms, which is mirrored by the US government. Meanwhile, the EU has set an RDI of 600 micrograms, with 1.1mg as TUL; the WHO’s TUL is 1mg. Over in Japan, due to a seaweed-rich diet they consume far more iodine, on average 50-80mg.

How much iodine you should consume will also depend on your age and gender, as the table below illustrates.

iodine by age group

The important thing to remember is everything in moderation, and listen to your body.

So there are side effects if I have too much iodine?

Too much iodine can be over-stimulating, and lead to an overactive thyroid, a condition known as hyperthyroidism. Generally, side effects are minimal but may include dizziness, tiredness, fever, vomiting and abdominal pain. If you suspect you’ve consumed too much iodine, ease off the seaweed and drink plenty of water. This will help to flush out excess iodine.

How do I find a happy medium then?

Mara Seaweed is your best natural source of iodine. One serving (2g or 1 tsp) will provide you with your recommended daily amount of iodine and it’s easily added to food during cooking as a seasoning. Far more enjoyable than taking a pill and much more delicious!

Sold! Where can I get some of this thyroid-friendly seaweed?

Visit Mara's shop and use SEASKEPTIC to get 15% off your first order. For ideas on how to use Mara Seaweed, visit our recipe pages


With thanks to the following for resources:


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