Objectives: To examine dietary iodine sources and to estimate the dietary iodine intake of the Norwegian population. Design: Food iodine analyses carried out in Norway during the last 10 years were compiled, and iodine intake calculated on the basis of food intake data from nationwide dietary surveys among children and adults. The food intake of adults was measured by a self-administrated food-frequency questionnaire, which covered habitual diet during the past year. The food intake of children was measured by dietary record during four consecutive days. Setting: Neither household nor industrial iodisation of salt is mandatory in Norway, but some brands of table salt have 5 mg of iodine added per gram of NaCl. In spite of this, the population has been considered iodine-replete for decades, i.e. having an iodine intake well above the Recommended Dietary Allowance of 150 mg day 21. This assumption has not been substantiated by dietary surveys. Subjects: The adults included 1374 females and 1298 males aged 16 -79 years. The children included 185 girls and 206 boys aged 4 years, 411 girls and 404 boys aged 9 years, and 517 girls and 492 boys aged 13 years. Results: The calculated iodine intake was in the range of 100-250 mg day 21 in the majority of the adult population. The mean iodine intake was 136 mg day 21(170 mg I/10 MJ) among women and 176 mg day 21 (161 mg I/10 MJ) among men. For children the iodine intake was in the range of 100-120 mg day 21. Milk and dairy products contributed approximately 55% and 70% of the dietary iodine intake in adults and children, respectively. Fish contributed more than 20% of the iodine intake in adults and about 10% in children. The iodine contribution of drinking water was negligible. Conclusions: While fish has the highest natural concentration of iodine and as such is an excellent iodine source, milk and diary products are the main determinants of iodine intake in the Norwegian population. Iodisation of cow fodder has been mandatory in Norway since 1950 and provides an efficient alternative to universal salt iodisation. Our results show that the dietary iodine intake of adults is in the range considered to be sufficient. The dietary intake of iodine was at recommended levels among the youngest children; however, it decreased among adolescents, especially among girls.

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 mg/l, range 63 -122 mg/l) compared with low-fat milk from the winter season (232 mg/l, range 103-272 mg/l). The median iodine concentration of organic summer milk (60 mg/l) was significantly lower than the iodine concentration of organic winter milk (127 mg/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 mg/kg) than the median iodine concentration in casein cheeses such as Jarlsberg and Norvegia of 201 and 414 mg/kg, respectively. With a recommended iodine intake of 150 mg/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.

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A study was conducted to determine the dietary iron requirement of fingerling Atlantic salmon Salmo salar L. During the first 4 weeks of the experiment, fish with an initial weight of 5 g were fed a casein–gelatine‐based purified diet which contained 11 mg iron kg−1. Thereafter duplicate tanks (200 fish in each) were fed the casein–gelatine purified diets containing supplemental iron levels of 0, 10, 20, 30, 40, 60, 100, 200 or 400 mg iron kg−1 (added as FeSO−4* 7H2O) for 12 weeks. Weight gain, body length and mortality were monitored. Liver iron and ascorbic acid concentration were analysed in addition to whole‐body iron, manganese and zinc concentration. Several haematological parameters were also measured. There were no significant differences in weight gain and survival of salmon fed diets containing different iron levels. Haematological values, hepatic and whole‐body iron concentrations were, however, significantly affected by the dietary iron content. Liver vitamin C concentration decreased with increasing dietary iron levels. Dietary supplementation with iron significantly reduced whole‐body manganese, but no effect of dietary iron on whole‐body zinc was found. Based on haematology and hepatic iron concentration, the iron requirement of Atlantic salmon was determined to be between 60 and 100 mg iron kg1.

Background/Aims: A food frequency questionnaire (FFQ) and a database for dietary supplements were developed for use in the Norwegian Mother and Child Cohort Study (MoBa). The aim of the present study was to investigate the relation between reported use and biomarkers in supplement and nonsupplement users and to validate self-reported intake of dietary supplements in mid pregnancy. Method: 120 women were recruited from MoBa, and 119 subjects completed the MoBa FFQ and a 4-day weighed food diary. Information on supplement use was collected by both methods. Venous blood specimens and 24-hour urine samples were obtained for measurement of dietary biomarkers. Results: Biomarker concentration/excretion and intake differed significantly between supplement and nonsupplement users for vitamin D, carotenoids, folate, the n–6/n–3 fatty acid ratio and iodine (p < 0.05 for all variables). Flavonoid excretion was higher in flavonoid-supplement users (p < 0.05). Significant correlations between total dietary intake (food and supplements) and biomarker concentration/excretion were found for vitamin D (r = 0.45, p < 0.001), folate (r = 0.26, p = 0.005), the n–6/n–3 fatty acid ratio (r = 0.36, p < 0.001) and iodine (r = 0.42, p < 0.001). Conclusion: The biochemical indicators examined in this study confirmed differences in self-reported micronutrient intake between supplement and nonsupplement users for vitamin D, beta-carotene, folate, n–3 fatty acids, flavonoids and iodine.

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The present study showed that 24-h urinary iodine excretion may be a useful biomarker for validating the intake of milk and dairy products in pregnant Norwegian women.