Jodmangel
Iodine deficiency was previously a common disease in Norway, because the content of iodine in the drinking water was low. Before 1950 goiter was a widespread disease caused by iodine deficiency. Up to 80 per cent of the population were affected in inland areas. In the coastal communities, saltwater fish were an important part of the diet, and because of the presence of iodine in seawater, goiter was less common than in the inland districts. From the 1950s, Norwegians started adding iodine to dairy cow feed. Since milk was an essential part of the Norwegian diet, the incidence of goiter decreased in the population.