Content, bio-accessibility and intake of iodine from seaweed-containing food products available in The Netherlands

Consumption of seaweed products has become increasingly popular in certain consumer segments, but the high iodine content of some of these products is of concern. We aimed to 1) assess the amount of iodine present in a selection of seaweed products; 2) determine iodine bio-accessibility from these products; and 3) estimate the daily intake of iodine from seaweed-containing products by Dutch consumers.

Seaweed products were purchased and analysed for iodine content by ICP-MS. Bio-accessibility (solubility) of iodine was determined by a static in vitro digestion model (INFOGEST), which mimics human digestive processes. Data on dietary intake of iodine from seaweed and other food products were collected from 80 regular consumers of seaweed products with an online food frequency questionnaire over the last month.

Iodine content of the seaweed products ranged from < 0.1 to 7910 µg/g of fresh weight (3.5 to 36,975 µg/serving). Bio-accessibility of iodine ranged from 24 to 56%, and was higher in products that were processed to a higher degree. Median daily iodine intake of the respondents was 270 µg/day (range: 68-16,544 µg/day), with 25% of seaweed consumers exceeding the upper limit (UL) for iodine intake of 600 µg/day over the last month.

Iodine content was very high in several of the seaweed products, which was also reflected by the high proportion of seaweed consumers who structurally exceeded the UL. In vitro data suggest relatively low bioavailability of iodine from seaweed products, but this remains to be confirmed by in vivo studies.