Iodine: Effects, Requirements & the Thyroid

Germany lies far from the sea – and that is precisely why iodine is a perennial topic here. The soils are comparatively low in iodine, drinking water provides hardly any, and without iodised table salt and sea fish the supply quickly runs short. It is no surprise that the region is considered a mild iodine-deficiency area.

In short and to the point: iodine is an essential trace element that your body needs above all for the thyroid. It contributes to normal thyroid function and to the normal production of thyroid hormones. The requirement for adults is around 180–200 µg per day. Good sources are iodised table salt, sea fish and dairy products – in the case of thyroid disorders, iodine belongs in medical hands.

The key points at a glance

• Iodine contributes to normal thyroid function and the normal production of thyroid hormones.
• It also supports normal cognitive function, the nervous system and energy metabolism.
• The requirement is around 180–200 µg per day, the tolerable total amount 600 µg.
• The thyroid's most important partner is selenium.
• In the case of thyroid disorders, supplement only after consulting a doctor.

What iodine does in the body – the mechanism

Iodine is not an interchangeable building block but the central raw material for the thyroid hormones T3 (triiodothyronine) and T4 (thyroxine). The numbers in the names give it away: T4 carries four iodine atoms, T3 three. Without iodine, the thyroid simply cannot build these hormones. And these hormones are something like the accelerator pedal of metabolism – they control how quickly cells convert energy, and they influence body temperature, heartbeat, concentration and much more.

That is why the authorised claims for iodine are so fundamental: iodine contributes to normal thyroid function, to the normal production of thyroid hormones, to normal cognitive function, to the normal function of the nervous system, to normal energy metabolism and to the maintenance of normal skin. These claims apply when the supply is adequate and are not a promise of a cure.

How much iodine per day?

The German Nutrition Society (DGE) suggests around 180–200 µg per day for adults. The requirement rises considerably during pregnancy and breastfeeding, because the child is supplied as well. At the upper end, the EFSA draws a clear line: the tolerable total amount for adults is 600 µg per day. Iodine is therefore a trace element with a relatively narrow window – too little is a problem, but clearly too much is not one to ignore either.

Sources: salt, fish and seaweed

The most important iodine sources in everyday German life are iodised table salt, sea fish, dairy products and eggs. A special case is seaweed such as nori, kelp or kombu: it can contain enormous amounts of iodine, and the content varies greatly from batch to batch. Here restraint is advisable – the tolerable amount is quickly exceeded with strongly iodine-rich seaweed products.

Anyone eating a vegan diet who also avoids iodised salt finds it particularly hard to take in enough iodine – background in Nutrients for Vegans. With a purely plant-based diet, it is also worth looking at Nutrients for the Thyroid.

What research is investigating

That iodine is indispensable as a building block of thyroid hormones is established textbook knowledge – there is nothing to qualify here. Beyond that, research is looking at how iodine supply is developing in various population groups, what role iodine plays in early childhood development and how the interplay with selenium affects the thyroid. Intriguing and at the same time a reason for caution is the observation that both too little and too much iodine can strain the thyroid – which is why this trace element is not a candidate for hit-or-miss self-optimisation.

Iodine and selenium – the thyroid duo

An often overlooked point: the thyroid needs not only iodine but also selenium. Selenium is a component of enzymes involved in the conversion and protection of thyroid hormones, and it contributes to normal thyroid function. But this expressly does not mean dosing both up on your own initiative – especially around the thyroid, medical guidance is important. More in the Selenium Guide.

Caution with the thyroid – honestly assessed

Iodine and the thyroid are so closely linked that particular caution applies here. With existing thyroid disorders – such as an overactive or underactive thyroid or autoimmune thyroiditis (Hashimoto's) – additional iodine can be unfavourable depending on the situation and absolutely belongs in medical hands. You should also have any changes in the neck area checked by a doctor rather than supplementing on your own. Anyone taking thyroid medication will find notes in Dietary Supplements and Thyroid Medication. Signs of a short supply are covered in Iodine Deficiency: Signs. This article provides general information and does not replace medical advice.

Matching products from Scheunengut

You will find iodine products in the Iodine category – for example as capsules or in combination with other nutrients. For the interplay with the thyroid, it is worth looking at Selenium and the Thyroid category. All products are laboratory-tested and made in Germany.

Frequently asked questions (FAQ)

How much iodine does an adult need per day?

The DGE suggests around 180–200 µg per day for adults. During pregnancy and breastfeeding the requirement is higher. According to the EFSA, the tolerable total amount is 600 µg per day – too much iodine is just as much a concern as too little.

Why is iodine so important for the thyroid?

Iodine is the central building block of the thyroid hormones T3 and T4. Without enough iodine, the thyroid cannot produce these hormones in normal amounts. That is why iodine contributes to normal thyroid function and to the normal production of thyroid hormones.

Is seaweed a good source of iodine?

Seaweed such as kelp or nori sometimes contains a great deal of iodine, but the amount fluctuates strongly. That is precisely what makes it unpredictable: the tolerable amount can quickly be exceeded. Iodised table salt and sea fish are more easily controllable sources.

May I take iodine if I have a thyroid disorder?

Only after consulting a doctor. With an overactive or underactive thyroid or autoimmune thyroiditis, additional iodine can be unfavourable. Always clarify the amount and the sense of supplementing with your doctor.