Iodine and iodine deficiency

Iodine is a vital trace element that is required for the production of thyroid hormones and thus for important metabolic functions. It is mainly found in foods such as sea fish and seafood, but iodized salt enriched with the trace element can also help to prevent iodine deficiency. Here you can find out what we need iodine for, what role the  nutrient  plays in pregnancy and what symptoms you can use to identify an iodine deficiency. We will also explain to you when iodine tablets make sense and why the versatile substance is also used in radioiodine therapy, as a  disinfectant  or after a nuclear accident.

What is iodine?

Iodine (also iodine) is a trace element that is vital for us because it is needed for the build-up of thyroid hormones and thus for a functioning  metabolism  . However, the trace element cannot be produced by the human body itself. Therefore, intake must be through food.

From a chemical point of view, iodine is an element denoted by the letter I (iodine) on the periodic table.

What do you need iodine for?

As an essential component of the thyroid hormones, especially  thyroxine  (T3) and triiodothyronine (T4), iodine is indispensable for child growth, the development of the brain and nervous system, bone formation, energy metabolism and numerous other metabolic processes. All of our organs need iodine. Its effect on body temperature should also not be underestimated, as this could not be maintained without iodine. In particular, its function in connection with cell division and cell growth makes a sufficient iodine intake during pregnancy important.

If the body is permanently supplied with too little iodine, the thyroid gland can no longer produce enough hormones and can therefore no longer adequately fulfill its task.

In medicine, iodine is also used as a disinfectant, as an X-ray contrast medium and in radioiodine therapy.

Daily requirement: how much iodine do we need?

The daily requirement of iodine depends, among other things, on age, but also on the state of health. Healthy adults should consume around 200 micrograms (µg) of iodine per day. The following recommendations apply to daily iodine intake according to the German Society for Nutrition (DGE):

Alter Recommended daily requirement of iodine
0 to under 4 months 40 µg
4 months to less than 1 year 80 µg
1 to under 4 years 100 µg
4 to under 7 years 120 µg
7 to under 10 years 140 µg
10 to under 13 years 180 µg
13 to under 51 years 200 µg
from 51 years 180 µg

During  pregnancy  , women have an increased need for iodine and should consume 230 micrograms of iodine daily. An iodine intake of 260 micrograms per day is recommended during  breastfeeding  . The recommendations of the World Health Organization (WHO) are slightly lower than those of the DGE, only for babies under four months a higher intake is recommended.

According to the European Food Safety Authority (EFSA), the daily iodine intake for adults should not exceed 600 micrograms, and the upper limit for children is correspondingly lower. The Federal Office for Risk Assessment (BfR) even sets the maximum value a little lower: According to this, adults in Germany  should not take in more than 500 micrograms  per day.

The iodine metabolism can be affected by a lack of selenium,  zinc  or  iron  . In addition, foods such as radishes, cress,  flaxcabbage  or millet, as well as smoking, can impair the absorption of iodine in the thyroid gland.

Which foods contain iodine?

Sea fish and seafood contain large amounts of iodine. The trace element is also found in  milk and eggs and in all foods that have been prepared with iodized salt ( salt  mixed with iodine  ). Iodized salt contains 1.5 to 2.5 milligrams of iodine per 100 grams of salt. Since the iodine content in soil is very low, foods from arable farming usually provide very little iodine.

The following foods with iodine are suitable for optimal iodine supply:

  • Sea fish (e.g. haddock, saithe, cod or plaice)
  • Seafood (e.g. mussels or oysters)
  • eggs, milk and dairy products
  • Foodstuffs with iodised table salt (e.g. meat, sausage and  bread )
  • Jodsalz

Seaweed and seaweed (especially brown algae such as arame, kombu, wakame and hijiki) also contain a lot of iodine, as the substance accumulates in them. Dried algae products in particular can therefore lead to the recommended daily dose being exceeded, even when consumed in small quantities, which can have negative effects on health. When buying  algae  , be sure to pay attention to the relevant warnings on the packaging.

Iodine deficiency: recognize symptoms

Many people consume too little iodine. Depending on the amount of iodine in the soil and thus the iodine content of crops, iodine deficiency can increase regionally. Inhabitants of countries in which less fish and seafood are consumed are also more likely to be affected by insufficient iodine supply. According to the Federal Institute for Risk Assessment, almost a third of adults and 44 percent of children and young people in Germany take in too little iodine.

Iodine deficiency often causes no symptoms for a long time. Externally visible signs of an iodine deficiency can be a  goiter (goiter)  , i.e. an enlarged thyroid gland, with which the body tries to compensate for the deficiency. This iodine deficiency goiter can lead, among other things, to problems with swallowing or wheezing. Iodine deficiency can also impair fertility and cause menstrual disorders in women.

Iodine deficiency during pregnancy  or in newborns and small children can have particularly serious consequences  . There is a risk of serious, irreversible developmental disorders of the skeletal and nervous systems, including cretinism. Miscarriages and stillbirths can also be the result of severe iodine deficiency during pregnancy.

The diagnosis of a deficiency is made, among other things, by a  blood test  to determine the  thyroid  levels and the thyroid-stimulating hormone (TSH value).

Symptoms of hypothyroidism due to iodine deficiency

Chronic iodine deficiency can  result in hypothyroidism  . Possible symptoms are:

  • fatigue  and weakness
  • Reduced performance (physical and mental) and lack of concentration
  • weight gain
  • Pale,  dry skinbrittle nails  and hair loss
  • slowed heartbeat
  • loss of appetite
  • constipation
  • depressive  moods
  • sensitivity to cold
  • slight increase in TSH value

In addition, however, an iodine deficiency can also lead to so-called “hot thyroid nodules” and an  overactive thyroid gland  (hyperthyroidism), which can manifest itself in the opposite symptoms, such as weight loss,  food cravings  and restlessness.

Preventing iodine deficiency: What can you do about iodine deficiency?

In Germany, the natural iodine content in food is not sufficient for a satisfactory iodine supply. In order to prevent iodine deficiency, the iodized salt ordinance was passed in 1989, which allows small amounts of the trace element to be added to conventional table salt.

In the meantime, iodized salt (iodised table salt) is used in many German households. Iodine is also used as an additive in animal feed, which has led to higher levels of iodine in dairy products and eggs. Since then, iodine deficiency has only been relatively rare in Germany – in 2021, however, the Federal Institute for Risk Assessment reported that the iodine supply in this country was declining again and the population was not optimally supplied.

In addition to eating foods containing iodine, such as sea fish and dairy products, you should also make sure that you use iodized salt in your own household. If necessary, the need can also be covered with the help of iodine tablets after consulting a doctor. As a rule, however, tablets or iodine-containing supplements are not necessary to correct an iodine deficiency or to prevent it from developing.

When does it make sense to take iodine tablets?

In certain cases, taking iodine tablets with the active ingredient potassium iodide can be useful to prevent or treat iodine deficiency. One also speaks of iodide tablets.

For example, women who are pregnant or breastfeeding have an increased need for iodine. Even those who do not eat fish, eggs or dairy products (e.g. because of a vegetarian or vegan diet or  lactose intolerance ) or eat a very low-salt diet (e.g. because of  high blood pressure ) may not be getting enough iodine through their food. Then – after consulting a doctor – it may be advisable to take iodine tablets.

The dosage of the drug can vary:

  • After consultation with your gynecologist, pregnant and breastfeeding women are recommended a dose of 100 to 150 micrograms of iodide per day. For these special phases of life, there are also combination preparations with  folic acid  to buy, since the need for this vitamin is then also increased.
  • To prevent goiter, iodide is usually prescribed in doses of 100 or 200 micrograms.
  • Anyone who has an enlarged thyroid gland due to iodine deficiency should consume larger amounts of iodine. To reduce the size of a goiter, 200 to 500 micrograms of iodide are usually taken.

If symptoms of an overactive or underactive thyroid gland occur as a side effect of the tablets, you should seek medical advice immediately. Additional iodine intake is not advisable for certain thyroid diseases such as  Hashimoto’s thyroiditis .

Too much iodine – overdose rare

In Germany, an iodine overdose or iodine poisoning does not usually result from a normal diet, not even when using iodised salt: no more than 25 milligrams of iodine may be added to one kilogram of salt. An overdose is therefore often due to the improper use of iodine tablets. But some algae products also have a very high iodine content, so caution is advised when using them. In addition, medicines containing iodine, contrast media or disinfectants (as a result of absorption through the skin) can be responsible for an oversupply of the trace element.

A severe iodine overdose can manifest as a brassy  taste  in the mouth, increased salivation, and indigestion. A skin rash known as iodine acne is also one of the possible symptoms.

Too much iodine can cause an overactive thyroid, but excess can also trigger an underactive thyroid, causing goiter. Especially in the case of existing thyroid diseases such as  Graves’ disease  or Hashimoto’s thyroiditis, a so-called iodine excess can affect the function of the thyroid gland.

In healthy people, a single overdose of up to 1,000 micrograms per day is usually excreted in the urine without any consequences. However, older people in particular who grew up with an iodine deficiency can react very sensitively to large amounts of iodine.

Iodine in a nuclear emergency

During nuclear fission as a result of a nuclear accident, radioactive iodine is released. When these isotopes enter the human body, they are deposited in the thyroid gland. This can cause significant damage to the cells and even lead to thyroid cancer.

For this reason, the government stockpiles high-dose potassium iodide tablets for reactor accidents and other nuclear disasters, which are distributed to the population in such cases. If the iodine tablets are taken at the right time, this can protect the thyroid gland and block the absorption of radioactive iodine: The dangerous iodine can then no longer get into the thyroid gland.

Nevertheless, you should never take such potassium iodide tablets independently and without the express request of the responsible authorities, because the right time and the correct dosage are decisive in order to achieve the desired effect of an iodine blockade. Taking the iodine tablets on your own as a precaution not only fails to produce the desired effect, but can also lead to serious side effects as a result of undetected thyroid diseases or iodine allergies.

Due to the increased risk of side effects, iodine tablets are only recommended for people up to 45 years of age in the event of a nuclear accident.

iodine in medicine

In medicine, iodine is used in various forms. In so-called  radioiodine therapy  , radioactive iodine-131 is used to treat thyroid tumors. The thyroid absorbs and stores the iodine. When the iodine breaks down, radiation is produced which destroys the thyroid cells.

Iodine is also used in medicine as a  contrast  agent, for example to make vessels visible in computer tomography (CT).

Iodine is also used as  an antiseptic  . The disinfectant povidone-iodine, which is very popular in medicine, is a compound of iodine and polyvinylpyrrolidone (PVP, povidone). Characteristic of the antiseptic is its red-brown color. It is often used as an ointment or in liquid form (as a diluted solution) and can also be used on mucous membranes because it does not burn. In addition to open wounds, possible areas of application include fungal infections or inflammation. Trade names include Betaisodona®, Betadona® or Betadine®.

In contrast, tincture of iodine contains alcohol, among other things, and can therefore cause a strong, burning sensation. For this reason, povidone iodine has established itself as an antiseptic in medicine.

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