Salt iodization: Effectively combating iodine deficiency

Abstract

Iodine deficiency is a major nutritional problem worldwide. About 2.2 billion people are at risk of deficiency, according to the World Health Organization (WHO) (Hetzel BS. Bull World Health Organ 2002;80:410-17). In infants, a low blood level of thyroid hormones is the main factor responsible for damaging the developing brain. In Scandinavia, as in many other countries, a neonatal thyroid-stimulating hormone (TSH) screening programme has been successful in the early detection of congenital hypothyroidism. However, in both developed and developing countries a low intake of dietary iodine results in iodine deficiency. The most effective approach is to prevent iodine deficiency through universal salt iodization. WHO is now performing a worldwide mapping of iodine deficiency disorders (WHO Global IDD Database, www3.who.int/whosis/micronutrient/). In this issue of Scandinavian Journal of Nutrition (SJN), Maria Andersson et al., from WHO, describe the ongoing work. Furthermore, a study of iodine intake and iodine status in two groups of Norwegians is published by Lisbeth Dahl et al. In Norway the main sources of dietary iodine are milk and dairy products, as well as fish and fish products, which contribute about 80% of the iodine intake. In other European countries iodinated salt, meat, bread and milk products contribute a major part of the iodine intake. In the Norwegian study the contribution of iodine from supplements or from iodized salt was not included in the calculations, since only some brands of table salt in Norway are fortified with iodine. The study by Dahl et al. combines an estimation of iodine intake in the diet with urinary iodine concentrations and serum levels of TSH and free thyroid hormone. Some population groups have a very low intake of iodine, which is an important finding. The material is, however, relatively small and the methodology is debatable. Nationwide studies in all countries are needed, and in Norway such a study is in progress. The authors conclude that iodization of table salt in Norway is too low to secure sufficient iodine intake for all people.