12th IFDC 2017 special issue – Iodine, selenium and iron contents in Portuguese key foods as consumed

Iodine Content of Wild and Farmed Seafood and Its Estimated Contribution to UK Dietary Iodine Intake

“…In terms of seafood groups, generally higher iodine contents were found in marine species compared to freshwater species, corroborating observations from previous studies [ 16 , 38 , 39 , 40 , 57 , 58 ]. Using the geometric mean, to account for the skewness of data between the different species within each seafood group, iodine levels were in the order of shellfish (39.3 µg·100 g −1 ) > marine fish (19.8 µg·100 g −1 ) > freshwater fish (6.4 µg·100 g −1 ) ( Table 2 ).…”

“…Overall, the mean and median iodine values of the samples studied were comparatively uniform with each other, generally indicating that the variation in iodine levels can be considered as low (see Table S1 for values). However, large variations in iodine contents are known to occur between individuals from the same species [ 1 , 38 , 40 , 51 , 52 ] and the present study is no exception. In particular, haddock (427.4 and 323.3 µg·100 g −1 flesh ww, mean and median, respectively), flathead grey mullet ( Mugil cephalus , 52.2 and 21.9 µg·100 g −1 ), wild turbot ( Psetta maxima , 52.0 and 34.6 µg·100 g −1 ), Atlantic mackerel ( Scomber scombrus , 34.4 and 23.3 µg·100 g −1 ), Atlantic herring ( Clupea harengus , 30.4 and 16.8 µg·100 g −1 ), Atlantic razor clam ( Ensis ensis , 26.9 and 15.7 µg·100 g −1 ), lemon sole ( Microstomus kitt , 26.1 and 15.5 µg·100 g −1 ), and sockeye salmon ( Oncorhynchus nerka , 24.9 and 13.3 µg·100 g −1 ) all exhibited sizeable differences between their respective mean and median values.…”

“…The nutritional and physiological status of an individual fish is predominantly influenced by season, which affects both food availability and reproductive status [ 53 ]. Delgado et al [ 38 ] found that mackerel and sardines ( Sardina pilchardus ) purchased from Portuguese markets tended to exhibit higher iodine contents in summer/autumn months compared to winter/spring. Similarly, Nerhus et al [ 40 ] observed higher iodine concentrations in haddock sampled during the latter part of the year, which they attributed to a repletion of elements following the April-May spawning period.…”

“…Conversely, the mean iodine content for sockeye salmon (13.3 µg·100 g −1 ) was observed to be in the range of all other salmon (9.9–17.0 µg·100 g −1 ). As previously discussed, there are several factors that may affect the iodine content within the same species of wild fish including season and location [ 38 , 40 ]. For the other farmed salmonid, rainbow trout ( O. mykiss ), no significant differences were observed between marine and freshwater reared trout (10.7 ± 5.5 and 11.6 ± 9.2 µg·100 g −1 ), with neither showing differences with wild sea trout ( S. trutta , 17.3 ± 3.4 µg·100 g −1 ) ( Figure 2 b).…”

“…Although the iodine contents of seafood have been studied (e.g., [ 15 , 37 , 38 , 39 , 40 , 41 , 42 ]), they are generally limited to only a few species most commonly consumed. Food composition tables such as McCance and Widdowson’s The Composition of Foods provide important nutrient information in assessing the health and nutritional status of populations [ 43 ], although they must be maintained and updated in order for the data to remain relevant [ 44 ].…”