Changes in iodine excretion in 50-69-y-old denizens of an Arctic society in transition and iodine excretion as a biomarker of the frequency of consumption of traditional inuit foods

Abstract

Background: Iodine intake in Greenland has been hypothesized to exceed 10 times the recommended amount. The transition from a traditional Arctic society may change the iodine intake, but no field studies have been performed. Objective: We aimed to ascertain iodine intakes, factors affecting iodine intake in circumpolar populations, and the usefulness of urinary iodine excretion as a biomarker for validation of Inuit food-frequency questionnaires. Design: Data were collected in a cohort study of 4 Greenland population groups: Inuit living in the capital city, the major town, and settlements in East Greenland and non-Inuit. Supplement use and lifestyle factors were evaluated with questionnaires, and dietary habits were ascertained with a food-frequency questionnaire. Iodine was measured in spot urine samples. Results: One percent of the population of Greenland was invited, and the participation rate was 95%. Less than 5% of Inuit but 55% of non-Inuit had urinary iodine excretion < 50 μg/24 h. Median urinary iodine excretion declined with the degree of decrease in the traditional lifestyle: it was 198, 195, 147, and 58 μg/24 h among Inuit in settlements, town, and city and in non-Inuit, respectively (P < 0.001). Participants were divided into diet groups calculated from Inuit food frequency. Iodine excretion decreased with increasing intake of imported foods (P < 0.001). In regression models, type of diet and the subject's lifestyle, sex, weight, ethnicity, and intake of iodine-containing supplements affected urinary iodine excretion. Conclusions: Circumpolar non-Inuit are at risk of iodine deficiency. Departure from the traditional Inuit diet lowers iodine intake, which should be monitored in Arctic societies. Urinary iodine excretion may be a useful biomarker of traditional Inuit food frequency. © 2005 American Society for Clinical Nutrition.