Concerns about the environmental impact of animal-source foods have led to a shift towards plant-based alternatives (PBA). While dairy products and seafood are rich in iodine, an essential nutrient for thyroid function and cognitive development, PBA often lack iodine fortification. As the market expands, there is increasing concern that individuals replacing dairy products and seafood with unfortified PBA may be at risk of iodine deficiency. This study assessed changes in the iodine fortification of plant-based milk, yogurt, cheese and seafood alternatives through a cross-sectional survey of UK supermarkets (2020–2024). Supermarkets were surveyed online each December, and product nutrition and ingredient data were extracted. Between 2020 and 2024, the number of PBA increased by 55 %, with 466 PBA identified in 2024, including milk (n 246), yogurt (n 81), cheese (n 110) and seafood alternatives (n 29). Iodine fortification was inconsistent: in 2024, 48 % of non-organic milk alternatives were fortified, while only 5 % of non-organic yogurt and 4 % of cheese alternatives contained iodine. In comparison, 28 %, 6 % and 0 % of non-organic milk, yogurt and cheese alternatives were fortified with iodine in 2020. No fortified seafood alternatives were identified. Fortified PBA provided 75–83 % of the iodine content of cow’s milk, but most remained poor iodine sources. Although iodine fortification has increased, it lags behind that of calcium and vitamin B12 (48 % v. 88 % and 71 %, respectively). Given iodine’s critical role in health, clearer public health guidance and improved fortification policies are needed. Increased reliance on PBA may exacerbate iodine insufficiency in the UK without intervention.

Current food systems pose risks to both population and environmental health. Reducing the intake of animal-based foods, such as dairy products, and increasing consumption of plant-based foods align with priorities for addressing climate change and promoting overall health. Plant-based alternatives to cow’s milk can be readily substituted for cow’s milk without altering meal patterns and food habits, making them a popular choice among those reducing animal-product consumption. However, plant-based milk alternatives do not necessarily provide the same nutrients as cow’s milk, particularly essential micronutrients like iodine. While national data indicate that the UK is iodine-replete, certain population subgroups (such as pregnant women, women of reproductive age, and vegans) remain at risk of iodine deficiency. Young women are more likely than other age groups to consume plant-based milk alternatives, heightening public health concerns about iodine insufficiency in this demographic. Current consumers of plant-based milk alternatives in the UK have lower iodine intake and status compared to consumers of cow’s milk. Population-level effects of replacing milk with plant-based alternatives vary and depend on factors such as the role of plant-based milk alternatives in the diet (i.e. in addition to, or as a replacement for milk), the presence of other iodine sources in the diet, the consumer’s life stage, and whether the alternatives are fortified with iodine. This review examines the literature on plant-based milk alternatives and iodine intake, focusing on implications of this dietary shift and strategies to improve iodine intake in those opting for plant-based milk alternatives in the UK population.