Dietary iodine intake and urinary iodine excretion in a Danish population: effect of geography, supplements and food choice

I deficiency diseases remain a health problem even in some developed countries. Therefore, measurement of I intake and knowledge about food choice related to I intake is important. We examined I intake in 4649 randomly selected participants from two cities in Denmark (Copenhagen and Aalborg) with an expected difference in I intake. I intake was assessed both by a food frequency questionnaire and by measuring I in casual urine samples. I excretion was expressed as a concentration and as estimated 24-h l excretion. Further, subgroups with low I intake were recognized. I intake was lower in Aalborg than in Copenhagen for all expressions, and lower than recommended in both cities if I intake from supplements was not included. Milk was the most important I source, accounting for about 44% of the I intake, and milk (P<0.001) and fish (P=0.009) intake was related to I excretion in a multiple linear regression model. Thus, risk groups for low I intake were individuals with a low milk intake, those with a low intake of fish and milk, those not taking I supplements and those living in Aalborg where the I content in drinking water is lower. Even individuals who followed the advice regarding intake of 200-300 g fish/week and 0.5 litres milk/d had an intake below the recommended level if living in Aalborg.