Iodine intake in Germany is not optimal – tips for ensuring an adequate iodine intake

Iodine is an essential trace element that must be taken up from food. It is primarily required for the production of thyroid hormones, which play a central role in regulating a wide range of metabolic processes in the body. Among other things, these hormones are necessary for normal growth, bone formation, brain development and energy metabolism. If iodine is taken up in amounts below the required level over a prolonged period, the thyroid gland produces too few hormones, which can lead to (in some cases serious) adverse health consequences.

A person’s iodine requirements vary from individual to individual and depend on several factors, such as age. The German Nutrition Society (DGE) updated its dietary recommendations for iodine in 2025. To ensure an optimal supply, the DGE now recommends age-specific iodine intakes of 80 micrograms per day (μg/day) for infants and 90 to 150 μg/day for children, adolescents and adults. Daily intakes of 220 and 230 μg are recommended for pregnant women and breastfeeding women respectively. 
The European Food Safety Authority (EFSAshort forEuropean Food Safety Authority) last derived reference intakes for iodine in 2014; the Authority considers an intake of 70 μg/day to be adequate for infants from 7 months of age, 90 to 120 μg/day for children aged 1 to 14 years, and 130 to 150 μg/day for adolescents aged 15 years and over and adults. For pregnant and breastfeeding women, EFSAshort forEuropean Food Safety Authority considers a daily intake of 200 μg to be appropriate.
 

^a Infants who are fed only home-made baby food should receive a supplement of approximately 50 μg of iodine per day.
^b In addition to a balanced diet containing iodised table salt, pregnant women should take a daily supplement containing 100 µgshort formicrogram (up to 150 µgshort formicrogram) of iodine. In the case of thyroid disorders, a doctor should be consulted before taking any supplements.
^c Whilst breastfeeding, in addition to a balanced diet containing iodised table salt, a supplement containing 
100 µgshort formicrogram per day should be taken.

According to EFSAshort forEuropean Food Safety Authority, a long-term intake of a maximum of 600 µgshort formicrogram of iodine per day does not represent a health risk for adults. For children, correspondingly lower tolerable upper intake levels (ULs) were derived depending on their age: 200 μg/day for 1- to 3-year-olds, 250 μg/day for 4- to 6-year-olds, 300 μg/day for 7- to 10-year-olds, 450 μg/day for 11- to 14-year-olds and 500 μg/day for 15- to 17-year-olds.

Since Germany has experienced prolonged iodine deficiency, which lasted until the 1980s, functional autonomy of the thyroid gland is still to be expected in the elderly in particular. These people may display higher sensitivity to iodine and may develop an overfunction of the thyroid gland as a result of excessive iodine intake. A ULshort forTolerable Upper Intake Level of 500 µgshort formicrogram/day for adults has therefore been set in Germany.

Pregnant women and women who are breastfeeding have an increased need for iodine due to their specific metabolic requirements. To reduce the risk of iodine deficiency and the potential health consequences for both mother and child, it is recommended that pregnant women and women who are breastfeeding take an iodine supplement after consulting their gynaecologist. In addition to a diet comprising foods naturally rich in iodine and those prepared using iodised salt, as well as the use of iodised salt when cooking at home, they should take an iodine supplement in tablet form at a dose of 100 to 150 μg per day

According to the European Food Safety Authority (EFSAshort forEuropean Food Safety Authority), long-term intake of up to 600 micrograms (μg) of iodine per day does not pose a health risk to adults. For children, correspondingly lower maximum intakes (tolerable upper intake levels, ULs) have been derived on an age-dependent basis: 200 μg/day for 1- to 3-year-olds, 250 μg/day for 4- to 6-year-olds, 300 μg/day for 7- to 10-year-olds, 450 μg/day for 11- to 14-year-olds and 500 μg/day for 15- to 17-year-olds.

‘Iodised salt prophylaxis’ is a health measure recommended by the World Health Organisation (WHO) which involves fortifying salt with iodine to prevent iodine deficiency and related diseases. In Germany, as in many other countries, the natural iodine content of food is insufficient to ensure an adequate iodine intake for the population. For this reason, the use of iodised table salt has been recommended in this country since the mid-1980s, both in the food industry and in food-related trades, as well as in private households.

In Germany, its use is voluntary; in other words, manufacturers can decide for themselves whether to use iodised table salt in food production and processing. The minimum and maximum levels of iodine in salt are regulated: the minimum level is currently 15 milligrams per kilogram (mgshort formilligram/kgshort forkilogram) and the maximum level is 25 mgshort formilligram/kgshort forkilogram of salt. One gram of salt therefore allows the body to take up approximately 15 to 25 micrograms (µgshort formicrogram) of iodine.
 

The minimum and maximum amounts of iodine that may be added to salt are regulated and range between 15 and 25 milligrams (mgshort formilligram) of iodine per kilogram (kgshort forkilogram) of salt. The maximum amount is set so that health effects are highly unlikely for both healthy people and those with thyroid conditions. Calculations by the Max Rubner Institute (MRIshort forMax Rubner Institute) have shown that even with 100 per cent utilisation of iodised salt in processed food and an above-average total iodine intake (from the usual diet), the risk of an iodine intake that is harmful to health is very low. The calculations are based on data from the National Consumption Study II, a study which assessed the nutrient intake of the German population aged between 14 and 80.

Compliance with the legally prescribed iodine levels is monitored by the food monitoring authorities. Furthermore, model calculations by the German Federal Institute for Risk Assessment (BfRshort forGerman Federal Institute for Risk Assessment) and the Max Rubner Institute (MRIshort forMax Rubner Institute) have shown that, even if the iodine content in salt were increased by 5 mgshort formilligram per kgshort forkilogram to a maximum of 30 mgshort formilligram per kgshort forkilogram of salt, no health effects would be expected at the current level of iodised salt use. However, this measure alone would not significantly reduce the risk of insufficient iodine intake. A refinement in iodine intake would therefore only be possible if the level of iodised salt used in processed foods were also increased.
 

As iodine levels in the soil are low in this country, many agricultural products contain very little iodine. Although sea fish and seafood have high iodine levels, they do not contribute significantly to iodine intake due to the low frequency of consumption. Overall, the natural iodine content of our food is insufficient to ensure an adequate iodine intake for the population in Germany. Continuous iodine-enriched salt prophylaxis is therefore necessary.

Following the introduction of iodine deficiency prevention measures in the mid-1980s – which recommended the use of iodised table salt in the food industry, in artisan food production and in private households – iodine intake in Germany improved significantly in the years that followed. The use of iodine as a feed additive, which leads to higher iodine levels in milk and dairy produce, also contributed to this improvement. However, data from the Robert Koch Institute (RKI) show that the iodine intake of the German population has deteriorated again (External Link: German Adult Health Survey (DEGS; 2008 to 2011) ;External Link: Second wave of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS Wave 2; 2014 to 2017, in German only). At the same time, results from market surveys indicate that, in recent years, there has been a renewed decline in the use of iodised table salt in the production of processed food.

The medianClose dialogmedianMedianTo glossary daily iodine intake from conventional food, excluding iodised table salt, is around 75 micrograms (μg) for adults in Germany (estimated on the basis of urinary iodine excretion). This corresponds to half of the daily intake of 150 μg of iodine recommended by the German Nutrition Society (DGE) and the European Food Safety Authority (EFSAshort forEuropean Food Safety Authority) for adolescents and adults.

In order to achieve an adequate iodine intake among adolescents and adults with the current average iodine fortification of 20 milligrams per kilogram (mgshort formilligram/kgshort forkilogram) of salt, around 40 per cent of all processed foods would need to be produced using iodised salt. To ensure that children’s iodine intake meets the recommended levels, a roughly comparable rate of iodised salt use would be necessary; however, there are greater variations here due to age-dependent variations in recommended intake levels and differences in median salt consumption. The proportion of artisanally and industrially produced foods currently made with iodised salt is, however, far below this level.
 

As part of the National Reduction and Innovation Strategy for Sugar, Fat and Salt in Processed Foods (NRI), the concentrations of sugar, fat and salt in certain food groups have been reduced in Germany. The aim is to reduce the prevalence of overweight and obesity and the diseases often associated with them. However, the desirable reduction in salt intake may simultaneously lead to a reduced iodine intake via iodised table salt. Given the current average iodine content in salt of 20 milligrams per kilogram (mgshort formilligram/kgshort forkilogram) and a 10 per cent reduction in salt consumption, around 45 per cent of all foods would need to be produced using iodised salt to ensure an adequate iodine intake for the adult population (compared with 40 per cent without a reduction in salt consumption; see the question ‘What is the iodine intake with and without the use of iodised salt in foods?’). For children, the desirable level of iodised salt use under these conditions would be in a similar range; however, due to age-dependent variations in intake recommendations and differences in median salt consumption, there are greater fluctuations here.

If salt consumption were reduced by 10 per cent whilst the iodine content in salt were increased by 5 mgshort formilligram/kgshort forkilogram – i.e. to an average of 25 milligrams per kilogram (mgshort formilligram/kgshort forkilogram) of salt, approximately 36 per cent of all foodstuffs would need to be produced using iodised salt to ensure an adequate iodine intake for the adult population (compared with 45 per cent without an increase in iodine content; see the question ‘What is the iodine intake with and without the use of iodised salt in food?’). For children, the desirable level of iodised salt use under these conditions would be in a similar range; however, due to age-dependent variations in intake recommendations and differences in median salt consumption, there are greater fluctuations here.

As early as 2019, a market survey by the University of Giessen showed that the recommendation to use iodised table salt in processed foods in Germany is only partially implemented. Overall, less than 30 per cent of food products made with salt contained iodised salt.

More recent representative product monitoring data from the Max Rubner Institute (MRIshort forMax Rubner Institute) even show a downward trend in the use of iodised salt: according to the 2025 survey, the proportion of processed foods containing iodised salt in the product groups examined – bread and small baked goods, sausages and other meat products – from 2020 to 2025: from 13 to 9 per cent for bread and small baked goods, from 48 to 34 per cent for sausages, and from 19 to 16 per cent for other meat products. The use of iodised salt in stews also fell from 29 per cent in 2022 to 19 per cent in 2025. A supplementary evaluation of product monitoring data from 2024 also showed a reduction in the use of iodised salt between 2021 and 2024 in cold sauces, including ketchup, from 2.4 per cent to 1.3 per cent, and in meat and sausage substitutes from 6.4 per cent to 5.7 per cent.

In organic products in particular, little to no iodised table salt is used (see the question ‘How much iodine do organic foods contain?’).
 

Iodine is found primarily in animal food products, although the iodine content can vary considerably within a single food category. As soil iodine levels are low in this country, local agricultural products contain very little iodine. Sea fish is naturally rich in iodine, but is not consumed very frequently.

Seaweed also contains iodine; however, depending on the type of seaweed, the season, cultivation methods or processing, the iodine content in seaweed can be so high that consumption may pose health risks, particularly for vulnerable population groups such as pregnant women, women who are breastfeeding and people with thyroid disorders or impaired kidney function (see also the External Link:BfR opinion on this).

Milk and dairy products, on the other hand, are important sources of iodine, as iodine is added to cows’ feed and is thus passed into the milk. Furthermore, iodine is primarily taken up via iodised table salt and food produced using it. When iodised salt is used in food, bread, sausages and other meat products are also important sources of iodine. However, iodised salt is used only to a very limited extent in the production of organic food, particularly in bread and small baked goods.

Under the Organic Regulation, the use of iodised salt in organic food products is permitted; however, the direct fortification with iodine is generally prohibited. Organically produced plant-based drinks must therefore not contain any added pure iodine.

Although almost all organic trade associations permit the use of iodised salt in food processing, the results of market surveys indicate that iodised salt is used only to a very limited extent in the production of organic food, particularly in bread and small baked goods.

The use of iodine as a feed additive is also authorised on organic farms. Nevertheless, individual studies show that organic milk contains only around 60 to 85 per cent of the iodine found in conventionally produced milk. These differences are likely due to variations in the animals’ iodine intake, which may be either seasonal (pasture forage and reduced intake of iodine-containing supplementary feed often lead to lower iodine levels in milk during the grazing season) or due to a potentially lower overall use of feed containing additives (such as iodine, amongst others) on organic farms.

Iodine metabolism can be influenced by the supply of other nutrients, particularly selenium and iron. Both substances are components of enzymes that play an important role in the production of thyroid hormones.

Furthermore, a high intake of certain foods – such as cabbage, cress, radish, linseed or millet – can lead to reduced intake of iodine by the thyroid gland. The reason for this reduced intake is the formation of thiocyanate, which competes with iodide for binding to a transport protein that actively transports iodide into the thyroid gland. Cabbage, cress and radish contain glucosinolates, which are broken down into thiocyanate, amongst other compounds, whilst linseed and millet contain cyanogenic glycosides that can be converted into thiocyanate in the body. However, this is irrelevant when the amounts of these foods consumed are typical.

Of the environmental factors, smoking is particularly relevant, as thiocyanate is also produced in this context.

An adequate iodine intake is possible by ensuring the consumption of iodine-rich foods. This means that, when shopping, one should look out for foods produced using iodised salt (check the labelling or, for loose goods, ask whether iodised salt has been used). Iodised salt should also be used consistently when preparing meals at home.

It is also recommended to eat sea fish (e.g. cod, mackerel or herring) once or twice a week, as this provides omega-3 fatty acids as well as iodine. Pregnant women should take care to avoid predatory fish species (e.g. tuna, swordfish), as these are at the top of the marine food chain and may have higher concentrations of substances that are harmful to health. 
Finally, the daily consumption of milk and dairy produce contributes to iodine intake. It should be noted, however, that milk from organic farms may contain less iodine than that from conventional farms. 
 

When buying pre-packaged food, the list of ingredients on the label will indicate whether iodised salt was used in its production. For loose goods at a bakery or butcher’s, consumers can ask whether iodised salt is used.

Avoiding animal food products (meat, fish, milk, eggs) increases the risk of an inadequate iodine intake. People following a vegetarian or vegan diet should therefore take particular care to ensure an adequate iodine intake, as should consumers who have to avoid fish or dairy produce due to an allergy to cow’s milk or fish, or a lactose intolerance (see question: ‘How can consumers ensure an adequate iodine intake through their diet?’).

Women should ensure they have an adequate iodine as soon as they are planning a pregnancy, as iodine is important for the baby’s healthy growth and development. Children and adolescents also need sufficient iodine for their physical and mental development.

Finally, pregnant and breastfeeding women have an increased need for iodine due to their specific metabolic situation and should therefore take particular care to ensure an adequate iodine intake or, after consulting their gynaecologist, take 100 to 150 micrograms (μg) of iodine per day in tablet form.
 

People who wish to or need to limit their salt intake should ensure they consume foods with naturally higher iodine content, such as sea fish (1 to 2 times a week) or milk and dairy produce. Particularly when reducing salt intake, iodised salt should be used consistently instead of non-iodised salt, and when choosing processed foods, those containing iodised salt should be preferred. If necessary, you should discuss with a doctor whether taking iodine tablets is advisable.

Milk and dairy produce are one of the main sources of iodine for humans. The iodine content in milk varies between 100 and 150 micrograms per litre (μg/l). The iodine intake of dairy cows via their feed plays an important role here. Furthermore, animal feed may contain substances that inhibit iodine absorption (e.g. glucosinolates). Seasonal variations in husbandry practices (indoor and pasture rearing) as well as the use of iodine-containing udder disinfectants can also influence the iodine content in milk. 

Studies have shown that organic milk contains only around 60 to 85 per cent of the iodine found in conventionally produced milk (see also the question ‘How much iodine do organic foods contain?’).

 

The main ingredients of plant-based drinks, such as grains (e.g. oats, rice), nuts (e.g. almonds, cashews) or pulses (e.g. soya, peas), contain very little iodine, which is why these drinks are also very low in iodine unless they have been fortified with it. As conventional milk is one of the most important sources of iodine, people who drink plant-based drinks (either exclusively or in part) instead of conventional milk are at increased risk of an inadequate iodine intake. The BfRshort forGerman Federal Institute for Risk Assessment therefore recommends – in contrast to the previous recommendation to fortify only salt with iodine – that plant-based drinks should also be fortified with iodine. The iodine content of fortified plant-based drinks should correspond to the natural iodine concentration in milk (median: 14 micrograms per 100 millilitres

Seaweed is sustainable and rich in nutrients. However, iodine levels in seaweed can be particularly high because the iodine contained in seawater is taken up by seaweed and, in some species, heavily concentrated. Iodine levels vary considerably depending on the type of seaweed, the season, cultivation methods or processing.

Marine macroalgae, commonly referred to as seaweed, are classified according to their pigment composition into brown algae (Phaeophyceae), red algae (Rhodophyta) and green algae (Chlorophyta). Brown algae in particular, especially species of the genera Laminaria and Saccharina (collectively known as ‘kombu’), can have very high iodine content (on average around 2,000 milligrams (mgshort formilligram) per kilogram (kgshort forkilogram) of dry weight), but the brown alga wakame is also relatively rich in iodine (on average around 200 mgshort formilligram per kgshort forkilogram of dry weight). Red algae, such as nori, usually contain significantly lower amounts of iodine (on average around 80 mgshort formilligram per kgshort forkilogram of dry weight), whilst green algae, such as Ulva species, generally have low iodine contents.

Where iodine levels are high – as is the case, for example, with kombu – even 1 to 2 grams (g) of dried seaweed in a single portion of ready-to-eat food can result in the taking up of several thousand micrograms (µgshort formicrogram) of iodine – an amount far exceeding the tolerable maximum chronic iodine intake of 600 µgshort formicrogram per day for adults. Such a high (excessive) intake of iodine can lead to the occurrence of adverse health effects, depending on the dose and the sensitivity of the person consuming it. In particular, for at-risk groups – such as pregnant women or their unborn babies, infants and young children, or people with certain thyroid conditions – an acutely very high iodine intake and the resulting extreme excess of iodine in the thyroid gland can have adverse health effects. These include, for example, iodine-induced hyperthyroidism – which can in some cases be severe – or (prolonged) hypothyroidism.
 

At EU level, a maximum iodine concentration in seaweed is currently under discussion (as of autumn 2026). The proposed concentration is 1 gram (g) of iodine per kilogram (kgshort forkilogram) of dry matter. Calculations by the BfRshort forGerman Federal Institute for Risk Assessment have shown that the maximum level under discussion is suitable for reducing very high single-intake levels (‘exposure peaks’) when consuming seaweed or seaweed products. This can help to mitigate the acute hazards associated with excessive iodine intake from seaweed.

However, with regard to regular consumption and the resulting long-term iodine intake from seaweed and seaweed products, the maximum level under discussion would not be sufficient to ensure a safe level of iodine intake for all consumers of seaweed and seaweed products.

The maximum level of 0.02 g (20 mgshort formilligram) of iodine per kgshort forkilogram of dry matter, last recommended by the BfRshort forGerman Federal Institute for Risk Assessment in 2007, is no longer supported by the BfRshort forGerman Federal Institute for Risk Assessment, partly because it would be impracticable in reality, as even the average iodine levels in seaweed generally exceed this value.
 

Seaweed is sustainable and rich in nutrients. However, in order to adequately protect consumers from excessive iodine intake from seaweed and seaweed products, the BfRshort forGerman Federal Institute for Risk Assessment recommends mandatory labelling of iodine content, along with consumption guidelines and supplementary warnings on ready-to-eat end products.

Stating the iodine content alone is not considered sufficient, as actual iodine intake is largely determined by portion sizes, frequency of consumption and the method of preparation of the seaweed. Supplementary consumption guidelines can help to ensure the efficacyClose dialogefficacyPositive Predictive ValueTo glossary of limiting iodine intake from seaweed and seaweed products. When purchasing seaweed, care should therefore be taken to ensure that, in addition to the iodine content, consumption and preparation instructions are also listed on the label.
 

Generally, the iodine status of population groups is determined on the basis of iodine excreted in urine. The World Health Organisation (WHO) recommends measuring iodine in spontaneous urine and assigns a specific status to the respective urinary iodine concentration.

*Although breastfeeding women have the same requirements as pregnant women, the adequate median urine concentration is lower because iodine is also excreted via breast milk. 
 According to the World Health Organisation (WHO, 2007), modified.
 

However, the iodine concentration in spontaneous urine depends heavily on fluid intake. Depending on how much has been drunk, the urine may be ‘diluted’ or ‘concentrated’, which can lead to misjudgements of iodine status. The gold standard for assessing a population’s iodine status is therefore the measurement of daily iodine excretion in a 24-hour urine sample. However, collecting urine samples over an entire day is considerably more labour-intensive. By normalising against specific biochemical reference systems (creatinine), daily iodine excretion can also be estimated from spontaneous urine.
Another method for estimating the population’s iodine status involves determining the percentage of the population whose daily iodine intake is below the Estimated Average Requirement (EAR). Ideally, this proportion should be only 2 to 3 per cent. 
In principle, none of the laboratory methods listed are suitable for estimating an individual’s iodine status, as individual iodine excretion can vary greatly depending on iodine intake on a given day. To date, there are no laboratory analytical methods that can determine an individual’s iodine status with sufficient accuracy. However, a dietary history can help to estimateClose dialogestimateEstimateTo glossary an individual’s iodine intake to a reasonable degree.
 

The population’s iodine status can be estimated, amongst other things, on the basis of urinary iodine excretion (see question: ‘How is the population’s iodine status determined?’). As around 85 to 90 per cent of the iodine ingested in the diet is excreted in the urine (the remaining 10 to 15 per cent is lost through sweat and faeces), daily iodine intake can be estimated on the basis of the daily amount of iodine excreted. Representative data on urinary iodine excretion for the German population were collected as part of the Robert Koch Institute’s (RKI) national health surveys:External Link: ‘Study on the Health of Children and Adolescents in Germany’ (KiGGS study, survey period 2003 to 2006 and 2014 to 2017) andExternal Link: ‘Study on the Health of Adults in Germany’ (DEGS, survey period 2008 to 2011) (in German only). 

The data show that 32 per cent of the adults included in the study and 44 per cent of the children and adolescents included in the study in Germany have an iodine intake below the estimated average requirement and are therefore at health risk due to insufficient iodine intake. Among children and adolescents, the estimated daily iodine intake has fallen by 13 per cent since the KiGGS baseline survey (2003 to 2006). 

The health consequences of an inadequate iodine intake depend on its severity and duration.

Severe maternal iodine deficiency during pregnancy increases the risk of miscarriage and stillbirth, as well as physical and mental malformations in the child. In particular, severe iodine deficiency in the foetus and infant can lead to cretinism. Typical symptoms of cretinism include skeletal malformations (short stature), severe impairment of cognitive abilities (intellectual disability) and, in many cases, deafness and mutism. In the early 19th century, cretinism was a common condition in Europe, particularly in the Alpine region. Thanks to improved iodine intake and newborn screening, the occurrence of this condition has virtually disappeared in Europe.

In addition, there are also symptoms caused by moderate to mild iodine deficiency.

For example, prolonged iodine deficiency can lead to an enlargement of the thyroid gland (goitre). This enlargement represents a physiological adaptive response by the body to compensate for chronic iodine deficiency by producing more hormone-producing tissue. Where the enlargement is uniform, the condition is referred to as ‘diffuse goitre’, whilst where the enlargement involves the formation of nodules, it is termed ‘nodular goitre’. In so-called ‘cold nodules’, the cells have ceased to function and no longer produce thyroid hormones. The vast majority of cold nodules are benign; in very rare cases, they may be malignant. In so-called ‘hot’ nodules, active or overactive cells produce too much hormone regardless of the body’s needs (functional autonomy). ‘Hot’ nodules are usually benign. However, a sudden, very high intake of iodine can trigger an acute episode of hyperthyroidism, which in some cases can be a life-threatening metabolic disturbance (thyrotoxic crisis).

Functional autonomy often goes unrecognised, i.e. undiagnosed. Affected persons are particularly older people who lived through the period before the introduction of iodine prophylaxis and were therefore exposed to a more severe iodine deficiency over the long term.

Furthermore, chronic iodine deficiency can lead to hypothyroidism – characterised by reduced production of thyroid hormones – in both adults and children. In children and adolescents, hypothyroidism can result in reduced mental and physical performance as well as delayed development. Some studies have shown an improvement in certain cognitive functions following iodine supplementation in children with mild to moderate iodine deficiency.

The consequences of mild to moderate iodine deficiency during pregnancy have been studied to a lesser extent. Several studies indicate an association between mild iodine deficiency during pregnancy and reduced cognitive abilities in children. However, a clear causal relationship cannot be established from this.
 

An ‘excess of iodine’ is generally defined as an iodine intake of more than 1,000 micrograms (μg) per day. Causes of an excess of iodine may include the use of iodine-containing contrast agents and iodine-containing medicines, or the consumption of seaweed that is particularly rich in iodine.

Such a high intake cannot be achieved through a normal diet without seaweed – even when taking into account the use of iodised salt.
 

A healthy thyroid gland is able to physiologically compensate for even high intakes of iodine and adapt to an increased intake. This occurs via the so-called Wolff–Chaikoff effect, in which acute, excessive iodine intake leads to a temporary blockage of thyroid hormone synthesis. This mechanism serves as a safeguard against excessive hormone production. The excess iodine is shedded in the urine. After a few days, a healthy thyroid gland resumes its normal hormone synthesis, i.e. it ‘escapes’ the Wolff–Chaikoff effect. 

In the presence of existing thyroid disorders, these regulatory mechanisms may fail, leading to the occurrence of iodine-induced hyperthyroidism or hypothyroidism.

People with functional autonomy of the thyroid, for example, are particularly at risk. In this condition, the thyroid gland has so-called ‘hot’ nodules, which produce thyroid hormones independently of physiological requirements. The excess iodine is used uncontrollably by the ‘hot’ nodules for hormone production, which can lead to the formation of hyperthyroidism, sometimes of a severe nature. Functional autonomy may also be undiagnosed.

In people with Graves’ disease, an autoimmune disorder of the thyroid gland associated with hyperthyroidism (overactive thyroid), increased iodine intake can exacerbate the existing hyperthyroidism in addition to the underlying condition.

Furthermore, iodine-induced hyperthyroidism has also been observed in people with an enlarged thyroid gland (goitre) who otherwise have a normal (euthyroid) metabolic state. 

However, following high iodine exposureClose dialogexposureExposureTo glossary, the occurrence of iodine-induced hypothyroidism may also occur. The physiologically beneficial inhibition of hormone production following excessive iodine intake (the Wolff–Chaikoff effect) is temporary in people with healthy thyroids. In cases of Hashimoto’s thyroiditis, this inhibition may persist to some extent. However, even in foetuses, the mechanism for overcoming this inhibition is not yet fully developed by the 36th week of pregnancy. Consequently, very high iodine intake by the expectant mother can cause foetal hypothyroidism to form.

Breastfed infants may also develop a blockage in hormone production – and consequently, usually a temporary hypothyroidism – if the mother’s iodine intake is very high.

Furthermore, excessive iodine intake can have a negative impact on the course of autoimmune diseases such as Hashimoto’s thyroiditis or Graves’ disease. However, the mechanisms involved are not yet fully understood. 

In patients with dermatitis herpetiformis Duhring, a very high iodine intake can lead to the occurrence of an exacerbated skin reaction.

In hyperthyroidism, the thyroid gland produces too many thyroid hormones (free thyroxine (fT4) and triiodothyronine (fT3)). The occurrence of these symptoms can include a racing heart, irregular heartbeat, high blood pressure, unintentional weight loss, nervousness, hand tremors, sleep disturbances, increased sweating, diarrhoea and, in women, menstrual irregularities.

In hypothyroidism, the thyroid gland produces too little thyroid hormone (free thyroxine (fT4) and triiodothyronine (fT3)). The occurrence of these symptoms can include tiredness, weakness, reduced mental and physical performance, a reduced basal metabolic rate with weight gain, a slow heart rate, dry and pale skin, brittle nails, apathy, difficulty concentrating, loss of appetite, constipation and depressive moods.

Hashimoto’s thyroiditis refers to an inflammation of the thyroid gland which, in its early stages, can lead to hyperthyroidism, but which, as the condition progresses, usually results in hypothyroidism due to scarring and, in most cases, atrophy of the thyroid tissue. The condition is the result of an autoimmune reaction and is influenced by genetic factors. As the condition progresses, antibodies are produced against the body’s own thyroid tissue, and the thyroid gland becomes infiltrated with immune cells, leading to chronic inflammation of the thyroid. The persistent inflammation of the thyroid gland results in scarring and hypothyroidism.

The progression of this condition is very slow, meaning that the occurrence of hypothyroidism often does not occur until years or even decades after thyroid autoantibodies are first detected. However, a positive autoantibody titre does not always lead to Hashimoto’s disease and hypothyroidism; thyroid function may also remain normal throughout a person’s life.
 

Graves’ disease is an autoimmune disorder in which the immune system produces antibodies against a protein located on the so-called TSH (thyroid-stimulating hormone) receptors on the thyroid gland. fillerWhilst the release of TSH is subject to a feedback mechanism – meaning that the binding of TSH to this receptor leads to the production of thyroid hormones in line with the body’s needs – the binding of the antibody to the TSH receptor results in a persistently increased production of thyroid hormones and thus to hyperthyroidism.

This autoimmune disorder can also lead to protrusion of the eyes (endocrine orbitopathy) and fluid retention in the shins (pretibial myxoedema).

Yes, in both Hashimoto’s thyroiditis and Graves’ disease, consuming food made with iodised salt poses no health risk, as only relatively small amounts of iodine are taken up in this way. However, one should avoid additional high intakes of iodine, such as iodine-containing food supplements or seaweed with particularly high iodine content.

An allergy is a hypersensitivity reaction caused by the immune system being stimulated by an allergen. The iodine compounds used in iodised salt are too small to act as allergens.

However, allergies to iodine-containing products, such as X-ray contrast media, can occur. In suh cases, the allergen is the carrier substance to which the iodine is bound.
 

‘Iodine acne’ is an intolerance reaction accompanied by skin changes and occurs only when daily iodine intakes in the milligram or gram range – and thus far above the possible iodine intake based on iodine deficiency prevention and also far above the Tolerable Upper Intake Level (ULshort forTolerable Upper Intake Level) – are taken up. An iodine intake on this scale can result, for example, from taking iodine-containing medicines.