University of Surrey model: unfortified plant-based dairy substitutes raise iodine inadequacy in UK

Replacing dairy products, even partially, with unfortified plant-based alternatives may lead to deficiencies in vital nutrients, according to a modelling study by the University of Surrey and Queen's University Belfast. The work was published on 4 November 2026 in The Lancet Planetary Health, EurekAlert reports. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗ The authors describe it as the first study of its kind in the United Kingdom. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

The team used data from the National Diet and Nutrition Survey covering more than 3,500 people aged 18 months to 100 years. They modelled how replacing milk, yoghurt and cheese with commercially available plant-based alternatives affects intake of four micronutrients found in dairy: iodine, calcium, riboflavin and vitamin B12. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

Modelling method and scenarios

The researchers identified all foods and recipes in the survey that contain dairy and substituted an equal weight of plant-based alternatives. Because the composition of products on supermarket shelves varies, every alternative found in their earlier market survey had an equal chance of being selected. They then examined nutrient intake and whether fortification options could offset shortfalls without causing excess.

Four scenarios were compared: partial replacement under existing UK market fortification; partial replacement assuming mandatory fortification of the alternatives; existing fortification with mandatory iodine fortification of bread; and mandatory iodine fortification of both the alternatives and bread. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

Iodine is the most sensitive nutrient

Even modest replacement of dairy led to marked declines in all four micronutrients, with iodine the most sensitive. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗ Replacing 20 to 35 per cent of dairy under current market fortification raised iodine inadequacy among adolescent females from 54 to 65 per cent, and among women aged 19-49 from 32 to 42 per cent. At full replacement, iodine inadequacy reached 80 per cent in adolescent females and 72 per cent in adolescent males. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

Mandatory fortification of plant-based alternatives prevented the declines in micronutrient intake, although iodine remained inadequate in 59 per cent of adolescent females. Iodine-fortified bread reduced inadequacy in this group to 37 per cent. The results suggest that combining mandatory fortification of the alternatives with iodine-fortified bread is the most effective strategy. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗

Lead author Dr Sarah Bath said the UK lacks an iodine fortification policy such as universal salt iodisation, and that dairy is a major source of iodine in the country, while unfortified alternatives have very low iodine content. Co-author Dr Katie Nicol said government policy is needed to implement fortification. eurekalert.orgEurekAlerteurekalert.orgOpen source ↗