Iodine in Edible Seaweed, Its Absorption, Dietary Use, and Relation to Iodine Nutrition in Arctic People

Dietary iodine is important to human health, and both low and high iodine intake levels increase the risk of disease. Seaweed is rich in iodine and it is a common component in both Asian and in Arctic cuisines. While the intake and impact are known for Asian people, data are lacking for Arctic people. We aimed to (1) measure iodine content of dietary seaweeds in Greenland, (2) estimate iodine absorption, and (3) assess the impact on iodine intake in Arctic people. A hunter in East Greenland donated household seaweed for (1) measurement of iodine content and (2) ingestion of 45 g by each of eight individuals with subsequent urine collections. (3) In Ammassalik, 96% of 50-69-year-old Inuit reported on the frequency of intake of seaweed and provided a spot urine sample for iodine measurement. Seaweed species provided were Chondrus crispus and Ascophyllum nodosum. (1) The iodine content was 47 and 102 mg/g, respectively. (2) An estimated 1.1 and 1.9 mg of the ingested 2.1 and 4.6 of iodine in seaweed were excreted in the urine within 2 days. (3) More than two in three Inuit reported some dietary use, and 41% (109 of 268) reported a weekly intake of dietary seaweed, which was associated with iodine excretion. In conclusion, the iodine content of edible seaweeds in the Arctic is very high and bioavailable. Dietary intake contributed to the recommended iodine intake level, but marked variation in iodine excretion calls for evaluation of the impact on thyroid function.