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Iodised salt prophylaxis does not constitute a health risk for people with a thyroid gland disorder or allergies

39/2001, 07.12.2001

Important contribution to controlling iodine deficiency diseases in Germany

Again and again rumours circulate that the fortification of foods with iodine in the form of iodised salt or indirectly through the iodisation of feeds may damage the health of specific groups of people. Statements like that or publications cause concern amongst consumers and the manufacturers of products of this kind. This has prompted BgVV to expressly point out that the voluntary fortification of foods with iodine does not constitute a health risk either to people with a thyroid gland disorder or those with allergies. Quite the contrary! Iodised salt and the iodisation of feeds make an important contribution to the control of iodine deficiency diseases in Germany. The situation is different when very high amounts of iodine are taken in, e.g. through the administration of iodine-containing X-ray contrast media, iodine-containing medicinal products or disinfectants and the consumption of algae products with very high iodine levels. These iodine levels can constitute a health risk for people with a thyroid gland disorder and allergy sufferers. BgVV asks doctors and health authorities for their support in the differentiated and informed raising of awareness amongst patients and consumers.

Iodine is an essential nutrient and an important component in thyroxine which cannot be formed without iodine. The recommended food intake of iodine, depending on the age of infants, is 40-80 microgram/day (µg/d) and increases to up to 200 µg/d for adolescents and adults. The maximum level recommended in Germany is 500µg/d. As a consequence of the unfavourable geo-chemical conditions, the iodine content of indigenous agricultural products is not sufficient to guarantee an adequate supply of iodine. In 1996 the average daily intake of iodine was still just under 120 µg. As a consequence, around 40% of the German population was found to have an enlarged thyroid gland. Many of them suffer from hormonal imbalances and the ensuing health problems. Pregnant and lactating women are particularly at risk and, by extension, infants and small children. Although the situation has improved considerably in recent years, Germany is still considered to be an iodine deficiency region.

The use of iodised table salt is considered to be the "best way" of overcoming iodine deficiency diseases on the international stage. It is recommended by national and international organisations like the World Health Organisation (WHO) and has been practiced in Germany since 1959. In order to reliably prevent an overdose of iodine, maximum levels have been laid down for the iodine fortification of table salt (15-25 mg/kg salt) and feedstuffs for animals (10 mg/kg e.g. for cattle and pigs). Since then there has been an additional daily iodine intake of approximately 120-140 µg iodine from iodised salt and foods fortified with iodised salt. This is not expected to trigger an increase in hyperthyroidism (hyperthyreosis). This has been demonstrated in Switzerland where iodised table salt has been successfully used since 1922.

Only the chronic intake of unphysiologically high iodine doses (2000 µg and more per day) or the single administration of more than 100,000 µg/day can lead to a long-term block of iodine intake by the thyroid gland and then to thyroid insufficiency (hypothyreosis). Hypothyreosis triggered by high doses of iodine is clinically relevant in newborn babies; it may occur after the use of iodine-containing household disinfectants in conjunction with mothers or infants. Iodine-induced hypothyreosis may also occur after the consumption of seaweed with very high levels of iodine. This is not the same as iodine over-sensitivity or iodine allergy which may occur after the administration of iodine-containing X-ray media or the use of iodine-containing disinfectants or iodine-containing medicinal products. In this context, large-molecular compounds to which the iodine is bound, act as the allergens not the iodine itself. There is no information on an allergy to iodine or iodised salt.

A detailed BgVV opinion on "Iodine fortification of foods in Germany" is accessible (as German version only) on the BgVV homepage (www.bgvv.de) under "Lebensmittel/Nahrungsergänzungsmittel".

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