Effects of the Danish iodine fortification program: consequences for thyroid health in children and adults

The aim of this project is to investigate the consequences of iodine fortification in Denmark with focus on the increase in fortification in 2019. Thyroid diseases affect over 14% of the Danish population during the lifetime and constitute a significant burden on patients and the health care system. A large proportion of these diseases can be prevented by optimal iodine intake. Therefore, in Demark iodine was added to salt in 2000. However, it is important to monitor the effect of iodine fortification, as both too little and too much iodine can affect children's development and increase the risk of thyroid diseases in children and adults. After the implementation of the iodine fortification in 2000 marked changes in the incidence of thyroid diseases were observed; some types of thyroid disease fell while others rose. The level of iodine in salt was further increased by 50% in 2019 - from 13 to 20 mg/kg. Through this project, we will investigate iodine intake and thyroid health in adults before and after the increase in iodine fortification in 2019, and also measure iodine intake in children. In addition, we will investigate whether some individuals are further vulnerable, e.g. due to their individual genetic make-up, to the effects of iodine fortification and thereby provide important insights into the mechanisms behind the development of thyroid diseases and whether there is a need for an individualized preventive approach. The project will be carried out in close collaboration between experts within clinical thyroid disease, nutrition and epidemiology in order to utilize the strengths of each collaborator and create synergy. Food fortification is an effective and inexpensive preventive strategy to increase the whole population's intake of a micronutrient. It can, however both have beneficial and detrimental health effects and it is therefore essential to examine the consequences of fortification.