Iodine concentration in Norwegian milk and dairy products

The present study was conducted to determine the iodine concentration in Norwegian-produced milk and a selection of dairy products. The iodine concentration of eighty-five samples of milk and dairy products was analysed by inductively coupled plasma-MS. Low-fat milk and organic milk were sampled from nineteen and seven different locations in Norway, respectively, during the summer and winter season of 2000. Other milk and dairy products were chiefly collected during the summer season. Low-fat milk from the summer season had significantly lower median iodine concentration (88 mug/l, range 63-122 mug/l) compared with low-fat milk from the winter season (232 mug/l, range 103-272 mug/l). The median iodine concentration of organic summer milk (60 mug/l) was significantly lower than the iodine concentration of organic winter milk (127 mug/l). There were no significant differences in the low-fat-milk samples with regard to geographical sampling location. Whey cheese (Tine Gudbrandsdalsost) iodine concentration was significantly higher (803 mug/kg) than the median iodine concentration in casein cheeses such as Jarlsberg and Norvegia of 201 and 414 mug/kg, respectively. With a recommended iodine intake of 150 mug/d for adults, a daily intake of 0.4 litres milk meets the requirement with 25 % during the summer and more than 60 % during the winter season. Thus, milk and dairy products are important determinants of iodine intake in Norway.