Iodine is an essential mineral nutrient and a trace element. A “trace element” is one that is needed by the body in minute quantities while “essential” means that the body needs such a mineral but cannot produce it by itself. So it is important for your health to take sufficient iodine with food. About 90% of nutrition-sourced iodine is absorbed in the stomach and upper small intestine.
The iodine cycle
If you want to understand why iodine deficiency can occur even with balanced nutrition, a glance at the iodine cycle below explains how iodine reaches our food.
In nature, most iodine is found in the oceans as ionic iodide and compounded with other elements such as salts. This explains why sea fish and sea foods are generally good sources of iodine. The iodide ions in seawater oxidize into elemental iodine. Being volatile, it evaporates into the atmosphere above the oceans. Its good water solubility means that iodine concentration found in water droplets is very high when it returns to the soil in the form of rain. As a result, growing plants easily accumulate iodine and when they are eaten by animals, they form a source of iodine. Good alternative natural sources of iodine to fish and seafood are cereal grains, meat, eggs and milk.
Understanding this cycle, it is easier to imagine that the further a region is from the sea, the more iodine deficient the soil is. As described in the above cycle, it is evident that the majority of iodine in the environment is found in or around oceans. In inland areas iodine levels in the soil tend to deplete with the result that food and livestock in these regions is iodine deficient. Interestingly the last ice age saw a complete washout of iodine from soil in regions where there were no oceans.
The role of iodine
Iodine is necessary for normal thyroid gland functions. 70 to 80 percent of ingested iodine is concentrated in the thyroid – a classic endocrine gland. It is here that it is used for the synthesis of two important iodine containing thyroid hormones which are necessary for energy-yielding metabolic and physiological processes. Furthermore iodine is considered necessary for the normal production of thyroid hormones and thus for the normal functioning of the thyroid gland and for your health.
Thyroid hormones have distinct functions in the body during different growth phases. In the course of pregnancy and in early years, they regulate the growth and development of organs and they are needed for proper growth and physical as well as mental development. Thyroid hormones also play a vital role in adolescents and are also involved in a variety of adult body functions being responsible for:
- Activation of the nervous system leading to higher attention levels and quicker reflexes
- Acceleration of the heart beat and increase in heart contraction
- Decrease of resistance in peripheral blood vessels
- Increase in the basic metabolic rate • Increase in body temperature
The production of thyroid hormones in the thyroid gland is regulated via the pituitary gland through the release of the thyroid-stimulation-hormone (TSH).
Recommended daily iodine intake
The necessary daily intake depends on a person’s age. The United Nations International Children’s Fund (UNICEF), the International Council for Control of Iodine Deficiency Disorders (ICCIDD) and the World Health Organization (WHO) recommend the following amounts:
|Above 12 years, including adults
|Pregnant women or breastfeeding mothers
Different agencies recommend different intakes, ranging from 150 to 290 µg/day to meet iodine needs of non-pregnant, pregnant and breastfeeding women.
One is familiar with iodine deficiency disorders but handling them, once evident can be discomforting. Iodine deficiency is not an acute disease but develops unnoticed over time. Therefore it can be adequate to decide on preventive measures, especially in certain phases of life or when it is known that there are nutritional limitations.
As iodine is unevenly distributed in the environment and most of it is found in the oceans, soil and groundwater in regions far from the sea often become iodine deficient. Older, exposed soil surfaces in particular are more likely to have iodine leached away by erosion. Major mountain ranges like the Himalayas, the Andes, the Alps and flooded river valleys such as the Ganges are among the most severely iodine-deficient areas in the world. As the amount of iodine depends on the soil vegetation grows in, plants and vegetables in these regions have a low iodine concentration. Animals consuming food grown in these soils become iodine deficient as well. As a result, the consumption of vegetables, plants and livestock from these regions cannot deliver daily iodine requirements.
In addition, 90% of iodine intake is excreted by the kidneys.
As a result, if the recommended daily intake of iodine is not amassed, iodine deficiency may occur which can affect the production of thyroid hormones. If there are not enough of these in the body, this can result in many adverse consequences on growth and development in humans, which are collectively termed as iodine deficiency disorders or IDDs. Common problems that can occur are endemic iodine-deficiency goitre or increased occurrence of an underactive thyroid gland (hypothyroidism) in cases of moderate-to-severe iodine deficiency. Typically, hypothyroidism symptoms frequently include:
- 1. Tiredness
- 2. Problems with concentration
- 3. Decrease in work productivity
- 4. Apathy
- 5. Reduced mental functions
- 6. Lack of physical energy
The effects of thyroid hormones on virtually every cell in the body is manifest in the widespread clinical effects of their lack or excess:
|Tissue or organ
|Central nervous system
|In childhood: poor neurological development (cretinism)
|Nervousness, emotional lability, hyperkinesia, tremor
|In adulthood: slowed intellectual functions
|Skin or hair
|Pale, dry, puffy skin (myxedema); dry, brittle hair, brittle nails
|Pink, warm, moist skin; onycholysis of nails; intolerance to heat
|Decreased blood volume and cardiac output
|Increased cardiac output
|Modest weight gain, decreased motility (constipation)
|Weight loss, increased motility (loose motions)
|Low resting metabolic rate, decreased appetite, weight gain, cold intolerance, reduced body temperature
|Increased resting metabolic rate, increased appetite; weight loss;
Depending on age, iodine deficiency may lead to several disorders:
Iodine deficiency can be divided into different categories – depending on the level of iodine concentration measured in the urine.* As iodine is almost solely excreted by the kidneys, the concentration in the urine is a good marker for iodine deficiency.
|Median urinary iodine concentrations(µg/l)
|Adequate iodine nutrition
|Mild iodine deficiency
|Moderate iodine deficiency
|Severe iodine deficiency
* Applies to adults, but not to pregnant and lactating women
“Thyroid gland” and “goitre” are most common terms which people relate to iodine deficiency. There are several reasons for an increased goitre. This is why you should refer to a doctor when you think your goitre has increased. In the following we explain the relation of iodine deficiency and goitre which is called endemic iodine-deficiency goitre.
Goitre is an enlargement of the thyroid gland beyond normal sizes which are 18 ml for women and 25 ml for men. This enlargement is generally not cancerous but benign in nature. A goitre does not necessarily mean that the thyroid gland is malfunctioning. When caused by insufficient iodine intake with food it is called iodine-deficiency goitre. This condition is considered endemic in a population when more than 5 % of the 6 - 12 year-old children have enlarged thyroid glands.
The increase of the thyroid gland can be caused by numerous reasons. One of the major causes of goitre is iodine deficiency. The development of goitre or enlargement of the thyroid gland begins as an adaptive response when iodine available to the thyroid is not sufficient for adequate thyroid hormone production.
A goitre is not an illness in itself but a symptom which can occur in various conditions or disorders. And it can occur in combination with normal thyroid function and also with hyperactivity or a sub-function. In most cases the goitre will cause no symptoms, though depending on its location and growth speed, it can lead to difficulty in breathing or swallowing.
An estimated 1.9 billion people are at risk from iodine deficiency worldwide. Data reports indicate that inhabitants of 21 countries suffer from mild iodine deficiency and nine are moderately iodine deficient. On the other hand, more than 110 countries have an adequate iodine intake. However in these countries some subgroups such as vegans, vegetarians, weaned infants or those who do not use iodised salt may still be deficient in iodine.
Global iodine status
Europe has had the highest percentage of iodine-deficient children of school age compared with other WHO regions during the past decade. This is surprising because of its wealth, its high standards of health care and also because of European calls to monitor and eliminate iodine deficiency. For example in 2015 only 66% of children of school age in the WHO-monitored European region had an adequate iodine intake.
The advice given by public health authorities to counteract iodine deficiency sounds easy:
- Consume milk and dairy products daily.
- Eat saltwater fish once or twice a week.
- Only use iodised salt in the household.
- Give preference to foods including iodised salt.
But these recommendations are not as easy as they may sound for everybody: firstly you can never know exactly how much iodine your meals contain and therefore cannot be sure if you get the right amount of daily iodine. Secondly some specific groups of people need more daily iodine than others. For example pregnant women and breastfeeding mothers have an increased iodine requirement due to their changed metabolic conditions. Then there are people with hypertension who often have to restrict their daily salt intake. Those with an allergy to specific foods like cow’s milk or fish may have problems sourcing recommended daily amounts of iodine because they have to avoid such foods. The same also applies to people who refrain from eating some or all animal foods like meat, fish milk, and eggs. Vegetarians, vegans and people who have to keep to special diets have a greater iodine deficiency risk and must be very careful to ensure that they get enough iodine. And the risk of developing iodine deficiency is very high for those living in parts of the world with a low iodine status where vegetables, plants and livestock only contain small amounts of iodine.
Iodine supplementation with Iodomarin®
Supplementation is an easy and effective method of acquiring an adequate amount of iodine and prevent iodine deficiency for all of these groups. Taking Iodomarin® on a daily basis to meet the WHO recommended intake is one possibility to supplement iodine. Should the required amount of iodine in normal nutrition not be guaranteed, the iodine quantities set out below are to be taken additionally so as to prevent iodine deficiency:
Recommended iodide intake as indicated in the Iodomarin® package leaflet
- Infants and children: 50 to 100 μg Iodomarin® once daily
- Adolescents and adults: 100 to 200 μg Iodomarin® once daily
- Pregnant or breastfeeding women: 200 μg Iodomarin® once daily
These doses will supplement your daily iodine requirement and serve as an easy and convenient way to counter iodine deficiency and it consequences.
Your daily dietary habits and the iodine level in the food you eat will determine your personal iodine deficiency risk. As mentioned above, in theory you can ensure a sufficient supply of iodine with a healthy and balanced diet. In practice however, the situation is not always so easy, meaning that everybody could be at risk of developing iodine deficiency. And, as with many other diseases, early diagnosis of iodine deficiency is very important in order to start an appropriate therapy as early as possible.
There are some symptoms that can be caused by iodine deficiency and likewise by other diseases. Contact your doctor if you develop symptoms like:
- Problems with concentration
- Decrease in work productivity
- Reduced mental functions
- Lack of physical energy
Your doctor will perform some diagnostic tests to confirm an iodine deficiency. First the anamnesis is important for the doctor to acquire information about all the symptoms you have or about known thyroid diseases in your family. This will be followed by a physical evaluation of your body and an inspection of your thyroid. Then a blood test will be made to establish the concentration of thyroid-stimulation hormone (TSH), the hormone released by the pituitary gland which serves as a messenger for the thyroid gland when it comes to thyroxine production. This will be followed by ultrasonography of your thyroid. Should your doctor consider it necessary, s/he may perform a fine needle aspiration biopsy of the thyroid nodule to determine whether it is benign or malignant. To conclude your doctor will decide together with you which treatment will be best.
A daily intake of more than 500 μg/day is not necessary as it would provide no additional health benefit and theoretically could cause impaired thyroid function. A high-level intake of iodine may result in acute iodine poisoning, causing gastrointestinal or cardiovascular symptoms or even coma. The thyroid is capable of adjusting to a wide range of iodine intakes in healthy individuals with no iodine sufficiency or other health issues: these persons can tolerate up to 1 mg daily.