Iodine fortification of plant-based dairy and fish alternatives: the effect of substitution on iodine intake based on a market survey in the UK

Iodine deficiency has been demonstrated in UK women, which is of concern as iodine is required for fetal brain development during pregnancy. Plant-based diets are increasingly popular, especially with young females, which may affect iodine intake as the main dietary sources are dairy and fish; plant-based products are naturally low in iodine. We, therefore, aimed to (i) assess the iodine fortification of milk-, yoghurt-, cheese- and fish-alternative products available in UK supermarkets and (ii) model the impact that substitution with such products would have on iodine intake using portion-based scenarios. A cross-sectional survey of retail outlets was conducted in 2020 and nutritional data was extracted from food labels. We identified 300 products, including plant-based alternatives to: (i) milk (n=146), (ii) yoghurt (n=76), (iii) cheese (n=67), and (iv) fish (n=11). After excluding organic products (n=48), which cannot be fortified, only 28% (n=29) of milk alternatives and 6% (n=4) of yoghurt alternatives were fortified with iodine, compared to 88% (n=92) and 73% (n=51) respectively with calcium. No cheese alternative was fortified with iodine but 55% were fortified with calcium. None of the fish-alternatives were iodine-fortified. Substitution of three portions of dairy (milk/yoghurt/cheese) per day with unfortified alternatives would reduce iodine provision by 97.9% (124 vs. 2.6 µg) and substantially reduce the contribution to adult intake recommendations (83 vs. 1.8%). Our study highlights that the majority of plant-based alternatives are not iodine-fortified and that use of unfortified alternatives in place of dairy and fish may put consumers at risk of iodine deficiency.