Despite the worldwide use of iodine supplementation, iodine deficiency remains a serious health problem in Europe. In 2004, it was estimated that approximately 2 billion people worldwide were at risk of iodine deficiency, about 20% were in Europe. Even though cretinism, the most extreme manifestation of iodine deficiency, has almost disappeared in Europe, milder forms of iodine deficiency still pose a great concern. They can lead to thyroid disorders, reduced intellect, poor school performance or impaired work ability.
Article at a glanc:
- Iodine
- Iodine and its biological functions in the human body
- Iodine deficiency
- Risk groups and consequences of iodine deficiency
- Some substances can block the absorption or utilization of iodine
- Other uses of iodine
- Iodine excess
- Food sources of iodine
Iodine
Iodine is an important biogenic element that is essential for the proper development of the body. The name of the element is derived from the Greek word "iodes" = purple, because it forms dark purple plate-like crystals. This halogen element was discovered in 1811 by the French chemist Bernard Curtois in the ashes of seaweed. It is found only in compounds on land and most iodine is found in seawater, where it is present in the form of iodide and iodate.
Iodine and its biological functions in the human body
Iodine is most concentrated in the body in the thyroid gland, where approximately 70% of the total body iodine is found. Iodine can be also found in the ovaries, breast tissue, pituitary gland, eye, bile and salivary glands. Iodine is essential for the production of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), accounting for about 65% and 59% of their weight respectively.
Thyroid hormones regulate cellular metabolism, stimulate the use of oxygen by cells to produce energy, maintain a person's body temperature, and control the growth and development of the nervous system and organs, including the brain. Optimal levels of iodine and thyroid hormones are therefore essential especially during pregnancy for healthy growth and development of the fetus, and subsequently during childhood, especially the first three years of life.
Iodine deficiency
Unfortunately, iodine deficiency is a serious problem worldwide. It is estimated that iodine deficiency affects up to 2 billion people globally, with up to 50% of the European population. One of the causes of iodine deficiency is the low concentration of this element in the soil, which varies widely from region to region. As a gas from the sea, iodine reaches land where it subsequently falls. Coastal areas therefore have higher iodine levels than inland and mountainous areas.
The situation in the Czech Republic
In March 2021, the Interministerial Commission for Addressing Iodine Deficiency organized the conference "Iodine 2021", which was attended by over 120 health professionals from all over the world, including the Czech Republic. The results of this conference, published by the State Institute of Health, highlighted the worsening situation of iodine deficiency worldwide, with the Czech Republic at risk of being removed from the list of countries with a solved iodine deficiency.
Risk groups and consequences of iodine deficiency
Pregnant women and children (mainly under 3 years of age) are the most at risk group. For pregnant women, iodine requirements may double due to the increased demands on the developing fetus. Severe deficiency of iodine, and hence thyroid hormones, during fetal development or infancy can lead to a disorder called cretinism, which causes irreversible mental and physical retardation.
Reduced intellectual ability
By having a major effect on the developing brain and myelination of the central nervous system, iodine deficiency can cause intellectual disorders and learning problems, especially in children. There are studies [1] [2] that show an association between low dietary iodine intake and reduced IQ (up to 13.5 points).
Thyroid disorders
Other manifestations of iodine deficiency include thyroid disorders. Individuals with a dietary iodine intake of less than 20 mcg/day often have hypothyroidism (=decreased thyroid function), which may be accompanied by goiter. Goiter may be the first clinical sign of iodine deficiency, when the thyroid gland tries to adapt by enlargement to the increased demands for thyrotropic hormone production. Other symptoms such as fatigue, constipation, muscle weakness, dry skin, decreased libido, irregular menstrual cycles and a tendency to gain weight easily are also associated with reduced thyroid function.
Some substances can block the absorption or utilization of iodine
The use or absorption of iodine can also be affected by, for example, chlorinated substances or the presence of goitrogens in the diet.
Chloramates (or perchlorates) are among the environmental contaminants that can inhibit iodine absorption by the thyroid gland, thereby reducing thyroid hormone production. These substances are therefore classified as endocrine disruptors, which enter the food chain through contaminated soil and water. Environmental pollution by perchlorates can be caused by the use of sodium hypochlorite used to disinfect water, the widespread use of nitrogen fertilizers or other sources such as fuel or fireworks.
Goitrogens, or strumigenic substances, found in cruciferous vegetables (such as cauliflower, broccoli, cabbage or kale) can inhibit the use of iodine and thus the subsequent synthesis of thyroid hormones. However, consumption of these foods in their raw state would have to be very high. On the other hand, cruciferous vegetables, which also have many health benefits, are rather absent from the diet of a large number of people.
Other uses of iodine
In addition to its use in the treatment of thyroid disorders (assuming iodine is the cause), iodine has other effects. On the surface, it acts as a powerful antiseptic that has been used topically as a disinfectant in the treatment of wounds for more than 170 years. The antimicrobial properties of iodine were already used in antiquity, when Aristotle's pupil Theophrastus described the pain relief from wounds after using seaweed. Iodine has a broad-spectrum antibacterial action and is also effective in killing molds, yeasts and viruses. Unlike other antibiotic and antiseptic agents, bacterial resistance to iodine has not developed, which is probably due to its broad mechanism of action.
Iodine also has a mucolytic effect, helping to dissolve mucus. This is one of the reasons why the use of a nasal teapot with vincentka to rinse the sinuses is effective for rhinitis. Iodine prevents the deposition of radioactive iodine in the thyroid gland, which is why it was used, for example, after the Chernobyl nuclear power plant explosion. It is also used in the treatment of breast diseases, especially fibrocystic breast disease. Breast tissue tenderness (e.g. in premenstrual syndrome) may also indicate iodine deficiency.
Iodine excess
After the start of the Russian-Ukrainian war, interest in iodine tablets increased due to concerns about possible radiation. It should be noted, however, that just as deficiency is harmful, excess iodine intake is also risky. Excessive intake can damage the thyroid gland. Manifestations of toxicity include vomiting, diarrhea, metallic taste in the mouth or headaches. EFSA has set an upper tolerable intake limit (UL) for adults of 600 mcg of iodine per day. EFSA also states that in the European population, the daily intake of iodine (from all sources) for adults is unlikely to exceed the upper tolerable intake.
Food sources of iodine
The amount of iodine needed varies according to age and gender. For adults, the daily recommended intake is 150 mcg, rising to 250 mcg per day for pregnant and breastfeeding women. The richest food sources of iodine are marine fish, seafood and seaweed. With seaweed, however, the species is very important. Kombu seaweed contains the most iodine, wakame seaweed less, and nori seaweed even less. Unrefined sea salt enriched with algae may therefore be a suitable source.
Sources:
[1] Bleichrodt N., Born P.M. A Meta-Analysis of Research on Iodine and Its Relationship to Cognitive Development. In: Stanbury J.B., editor. The Damaged Brain of Iodine Deficiency: Cognitive, Behavioral, Neuromotor and Educative Aspects. Cognizant Communication Corporation; New York, NY, USA: 1994. pp. 195–200.
[2] Bougma K, Aboud FE, Harding KB, Marquis GS. Iodine and mental development of children 5 years old and under: a systematic review and meta-analysis. Nutrients. 2013 Apr 22;5(4):1384-416. doi: 10.3390/nu5041384. Erratum in: Nutrients. 2014 Dec;6(12):5770-1. PMID: 23609774; PMCID: PMC3705354.
Bailey R, L, West Jr. K, P, Black R, E: The Epidemiology of Global Micronutrient Deficiencies. Ann Nutr Metab 2015;66(suppl 2):22-33. doi: 10.1159/000371618
Leung AM, Pearce EN, Braverman LE. Perchlorate, iodine and the thyroid. Best Pract Res Clin Endocrinol Metab. 2010 Feb;24(1):133-41. doi: 10.1016/j.beem.2009.08.009. PMID: 20172477; PMCID: PMC4137763.
World Health Organization. (2007). Iodine deficiency in Europe : a continuing public health problem. World Health Organization. https://apps.who.int/iris/handle/10665/43398
https://www.efsa.europa.eu/sites/default/files/efsa_rep/blobserver_assets/ndatolerableuil.pdf